April 2019 Outcrop by The Rocky Mountain Association of Geologists

OUTCROP Newsletter of the Rocky Mountain Association of Geologists

Volume 68 • No. 4 • April 2019

4/8-9/2019

1999 Broadway

April Short Course

Oil & Gas Law and Policy for Geologists Ralph Cantafio Ralph Cantafio, attorney at Feldmann Nagel Cantafio Margulis PLLC and lecturer at the University of Colorado Global Energy Management Program, will reprise his Oil and Gas Law for Geologists course, with updated information and an inside look a the Martinez case, Propositions 74 and 112, and Colorado Senate bill 181. Topics covered will include: The political environment of Colorado oil and gas law and regulation under the Polis administration; contract basics; oil and gas development contracts (upstream); the oil and gas lease; severed mineral estate; federal oil and gas leasing; the demise of the preemption doctrine in Colorado: Martinez, Propositions 74 & 112, Senate Bill 181 and the foreseeable political landscape of the oil and gas industry; joint operating agreements (JOAs) and farmouts. About the presenter: With an extensive history in law and knowledge of the Oil and Gas industry, Ralph practices oil and gas law in Alaska, Colorado, North Dakota, Texas, Utah, and Wyoming. Not only is Ralph a shareholder of a law firm, with offices located in Denver and Steamboat Springs, Colorado, that emphasizes oil and gas law, but he is also an adjunct professor teaching oil and gas related classes. Ralph currently teaches in the Global Energy Management Program taught at the University of Colorado Denver. Mr. Cantafio has also lectured foreign professionals, primarily from Nigeria and China, focusing on international oil and gas law, industry, as well as international natural resources law.

Member price: $225 Non-member price: $250

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OUTCROP | April 2019

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Vol. 68, No. 4 | www.rmag.org

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OUTCROP The Rocky Mountain Association of Geologists

1999 Broadway • Suite 730 • Denver, CO 80202 • 303-573-8621 The Rocky Mountain Association of Geologists (RMAG) is a nonprofit organization whose purposes are to promote interest in geology and allied sciences and their practical application, to foster scientific research and to encourage fellowship and cooperation among its members. The Outcrop is a monthly publication of the RMAG.

2019 OFFICERS AND BOARD OF DIRECTORS PRESIDENT

2st VICE PRESIDENT-ELECT

Tom Sperr tsperr@bayless-cos.com

Dan Bassett dbassett@sm-energy.com

RMAG STAFF EXECUTIVE DIRECTOR

Barbara Kuzmic bkuzmic@rmag.org

PRESIDENT-ELECT

TREASURER

Jane Estes-Jackson janeestesjackson@gmail.com

Eryn Bergin eryn.bergin@aec-denver.com

1st VICE PRESIDENT

TREASURER-ELECT

Heather LaReau heatherthegeologist@gmail.com

Chris Eisinger chris.eisinger@state.co.us

Kira Timm kira.k.timm@gmail.com

1st VICE PRESIDENT-ELECT

SECRETARY

Ben Burke bburke@hpres.com

Anna Phelps aphelps@sm-energy.com

Courtney Beck Courtney.Beck@halliburton.com

2nd VICE PRESIDENT

COUNSELOR

Sophie Berglund sberglund@raisaenergy.com

Donna Anderson danderso@rmi.net

PROJECTS SPECIALIST

Kathy Mitchell-Garton kmitchellgarton@rmag.org CO-EDITORS

Jesse Melick jesse.melick@bpx.com DESIGN/LAYOUT

Nate Silva nate@nate-silva.com

ADVERTISING INFORMATION

Rates and sizes can be found on page 48. Advertising rates apply to either black and white or color ads. Submit color ads in RGB color to be compatible with web format. Borders are recommended for advertisements that comprise less than one half page. Digital files must be PC compatible submitted in png, jpg, tif, pdf or eps formats at a minimum of 300 dpi. If you have any questions, please call the RMAG office at 303-573-8621. Ad copy, signed contract and payment must be received before advertising insertion. Contact the RMAG office for details. DEADLINES: Ad submissions are the 1st of every month for the following month’s publication.

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The Outcrop is a monthly publication of the Rocky Mountain Association of Geologists

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2ND ANNUAL RMAG

Geo Train to AAPG ACE Fort Worth to San Antonio MAY • 18 • 2019 $75 per person | one-way

Sponsored by

OUTCROP | April 2019

Vol. 68, No. 4 | www.rmag.org

OUTCROP Newsletter of the Rocky Mountain Association of Geologists

CONTENTS FEATURES

DEPARTMENTS

18 Lead Story: The Colorado Mineral Belt Composite Batholith and its Role in Explaining the Genesis of Ore Deposits

6 2019 RMAG Summit Sponsorship 12 RMAG March 2019 Board of Directors Meeting 14 President’s Letter

ASSOCIATION NEWS 2 RMAG April Short Course 4 RMAG Geo Train to San Antonio 11 RMAG Summit Sponsors 13 RMAG Golf Tournament 15 RMAG/DWLS Fall Symposium, Call For Papers 41 2019 Outcrop Cover Photo Competition 46 2019 RMAG Foundation Scholarship Winners

30 RMAG Luncheon programs: Lisa Morgan 32 RMAG Luncheon programs: Bob Raynolds 34 Mineral Of The Quarter: Rhodochrosite 47 Cartoon 48 Welcome New RMAG Members! 48 Outcrop Advertising Rates 49 In The Pipeline 50 Advertiser Index

COVER PHOTO Hanging Lake (located in Glenwood Canyon, Garfield County) was created when dissolved Carbonate from the Mississippian Leadville Formation precipitated as travertine gradually adding to the lake’s rim and ledges below. Photo by Steve Sturm.

50 Calendar

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OUTCROP | April 2019

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The Rocky Mountain Association of Geologists 910 16th Street, Suite 1214, Denver, CO, 80202 phone: 303.573.8621 | fax: 888.389.4090| email: staff@rmag.org

November 6, 2018 Dear Partners, 2018 was a very successful year at Rocky Mountain Association of Geologists. Our 2018 Summit Sponsors made it possible for us to host 37 separate educational and technical events, and 4 social events, in addition to assisting with overall operations. We simply cannot thank you enough! All of us here at RMAG are very excited for the 2019 Summit Sponsorship program, and we think you will be too. Program levels, benefits and pricing are remaining the same as 2018, but with one attractive addition, website advertising. RMAG has purchased new association management software (AMS) and a custom designed website. The new website will have a “click to open” advertiser’s page. 2019 Summit Sponsors, at all levels, will have ads placed on the advertiser’s page in addition to their monthly ads in The Outcrop. Platinum and Gold level Summit Sponsors will have the added benefit of publishing articles on the advertiser’s page. The advertiser’s page was modeled in part by the AAPG Explorer website, where companies can present their work to the public. Another Summit Sponsor website benefit will be company logos continually scrolling on the home page. Summit Sponsorship also includes no-cost training and social activities. These benefits are to use as you wish, for staff, vendors or guests. RMAG provides some of the highest quality, and industry relevant trainings in the country. We also like to have fun while networking with our annual golf tournament, and various other social activities throughout the year. If you company hasn’t previously been an RMAG Summit Sponsor, or it has been awhile since you were, please consider becoming a Summit Sponsor! RMAG maintains a membership base of 1800 throughout the year, the largest membership base of any geological-based association in the Rocky Mountain region, assuring your company broad exposure. Again, a sincere thank you to everyone who has supported RMAG throughout 2018! We are looking forward to our continued partnership and making new partners in 2019. Please contact me directly at bkuzmic@rmag.org , or 303-573-8621 x 2, if your or your company have any questions. Best Regards,

Barbara Kuzmic Executive Director Rocky Mountain Association of Geologists

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OUTCROP | April 2019

2019 RMAG Summit Sponsorship Platinum, Gold, Silver Sponsorship Level Contribution Level

Platinum

Gold

Silver

$10,000

$5,000

$2,500

$9,500 for returning 2018 sponsors

$4,500 for returning 2018 sponsors

RMAG Website Benefits

üMedium Logo

Large Logo & Link 4 Articles & 4 Large Ads

Medium Logo 2 Articles & 2 Medium Ads

The Outcrop (receive benefits for 12 issues, monthly online publication)*

ü Full page ad

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ü 1/2 page ad

Company logo listed as a 2019 annual sponsor in the Outcrop

üLarge Logo

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Company logo placed on 2019 Summit Sponsor signage at all monthly luncheons

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Opportunity to offer RMAG approved promotional items at luncheons

Company logo on 2019 Summit Sponsorship Website Page Articles & Ads on Special Advertiser's Website Page

4 Small Ads

Publications

Monthly Luncheons

2019 Continuing Education Event Tickets - Choice of 2 Events Platinum

Gold

Silver

Please choose two events and indicate your selections below. Each box counts as one event.

4 Core Workshop Tickets - including Hot Plays Core Workshop without Fall Symposium Tickets

2 Core Workshop Tickets - including Hot Plays Core Workshop without Fall Symposium

2 Short Course Tickets

1 Short Course Ticket

2 Fall SymposiumTickets

2 Fall Symposium Tickets

1 Fall Symposium Ticket

2 Fall Symposium Tickets - including Hot Plays Core Workshop (counts as two selections)

1 Fall Symposium Ticket - including Hot Plays Core Workshop (counts as two selections)

2 half price Tickets to the Fall Symposium and Hot Plays Core Workshop

* 12 months of Outcrop Advertising: Company logos and advertising information must be received no later than January 31st, 2019 to receive 12 total months. 12 total months includes January 2020. If received between January 31st and February 28th will receive 11 total months. All logos and advertising information must be received no later than January 15, 2019 to be included on Summit Sponsor signage. Previous Summit Sponsors only need to submit advertising information.

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2019 RMAG Summit Sponsorship Platinum, Gold, Silver RMAG 2019 Events

Platinum

Gold

Silver

Additional Tickets

Purchase additional 1/2 Price Continuing Education Event Tickets

ü3 total tickets for any event ü2 total tickets for any

event excludes Fall excludes Fall Symposium and Symposium and Hot Plays Hot Plays Core Workshop Core Workshop

No half price tickets at this level

RMAG Luncheons

ü 4 Total Tickets through

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Player tickets

ü 2 Teams of Four Players

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Event tickets

ü 4 Tickets

ü 2 Tickets

Company logo placed on 2019 Summit Sponsor signage

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Company logo looping in PowerPoint presentation

üLarge Logo

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Event Tickets

2019

Golf Tournament

Sporting Clay Tournament

Rockbusters Bash

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OUTCROP | April 2019

2019 RMAG Summit Sponsorship All sponsor benefit event tickets must meet RMAG event registration deadlines. All benefits end March 31, 2020 Discount to returning 2018 Summit Sponsors for 2019 Summit Sponsors only.

RMAG 2019 Summit Sponsorship Opportunities Platinum Sponsor Gold Sponsor Silver Sponsor

Deadline for sponsorship: March 31, 2019. Specify type of payment on signed form, and send logo to staff@rmag.org by 2/28/19. No benefits will be provided without payment. Company: Company Representative: Address: City/State/Zip: Phone:

Email:

Payment by Credit Card Select a card: Amex M/C VISA Discover Name as it appears on Credit Card:____________________________________________________ Credit Card #: Exp. Date: _________________ Security #: Signature: Payment by Check Mail checks payable to RMAG: Rocky Mountain Association of Geologists (RMAG) 1999 Broadway, Suite 730 Denver, CO, 80202

RMAG events are subject to change. Cancellation or rescheduling of events does not give sponsor right to refund. Summit Sponsors will receive benefits at any new events added into the RMAG schedule for 2019.

Thank you for your generous support!

email: staff@rmag.org

phone: 303.573.8621

OUTCROP | April 2019 Denver, CO, 80202 910 16th Street #1214,

fax: 888.389.4090 web: www.rmag.org Vol. 68, No. 4 | www.rmag.org follow: @rmagdenver

The Rocky Mountain Association of Geologists

2019 Summit Sponsors PLATINUM SPONSOR

GOLD SPONSORS

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OUTCROP | April 2019

RMAG MARCH 2019 BOARD OF DIRECTORS MEETING By Anna Phelps, Secretary aphelps@sm-energy.com

if you are a Rocky Mountain geologist working the Permian Basin, or another basin outside the Rockies, you now have a new venue for publication. Send those manuscripts over to the Mountain Geologist! The On the Rocks Committee has nine field trips planned for this summer, including family trips, fossil hunting trips, and a geology hike. Keep an eye out for field trip registration on the RMAG website. The Educational Outreach Committee continues to grow in members and will have a table at the career boot camp for the Denver Kids Program in March. April’s fun geology fact fun geology fact comes to us all the way from South China. Researchers recently found a new Burgess Shale–type fossil Lagerstätte with extremely well-preserved soft-bodied fossils. This Lagerstätte, which is part of the Cambrian Shuijingtou Formation, contains Qingjiang biota with very high diversity and 53% new taxa. This discovery rivals that of the Burgess Shale and Chengjiang biotas and will improve the understanding of the Cambrian explosion!

Happy Spring outcrop lovers! After some heavy snow on the Front Range, the lower elevation outcrops are coming back into view. It won’t be long now until we can get our hand lenses on the mountain outcrops! In the meantime, enjoy the lower elevation outcrops, and if you’re lucky, perhaps some Spring Break outcrop adventures in warmer weather. The March meeting of the RMAG Board of Directors was held on March 20, 2019 at 4:00 PM. All board members except Donna Anderson were present. Director Barbara Kuzmic reported that there are currently 1,514 RMAG members and we continue to see membership renewals come in. Publication sales were flat in February. There are 27 registrations for the March Intro to Unconventional Play Prospecting and Development Short Course and registration for the May Golf Tournament is open. Treasurer Eryn Bergin reported that the February Mudrock Petrography Short Course brought in good revenue for RMAG. Operating expenses continued to be high in February due to the office move. The Continuing Education Committee has five short courses booked for 2019 and many more in the hopper. The Committee also has great Luncheon speakers booked through the summer. The Publications Committee reported a new scope for the Mountain Geologist. The Mountain Geologist will now accept submissions encompassing any areas and basins being worked by geologists in the Rockies. So,

SOURCE

Fu, D., Tong, G., Dai, T., Liu, W., Yang, Y., Zhang, Y., Cui, L., Li, L., Yun, H., Wu, Y., Sun, A., Liu, C., Pei, W., Gaines, R.R., Zhang, X. (2019). The Qingjiang biota—A Burgess Shale–type fossil Lagerstätte from the early Cambrian of South China. Science, 363, 1338–1342.

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MAY

RMAG 2019

GOLF TOURNAMENT

Member team $600 Non-member team $700 //////////// Member individual $150 Non-member individual $175 //////////// ✓ Teams of 4 and individuals welcome to register ✓

Includes club entry, 18 holes of golf, cart, dinner and chance to win prizes!

A RROWHEAD G OLF C LUB 1:30pm shotgun email: staff@rmag.org

phone: 303.573.8621

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1999 Broadway, Suite 730, Denver, CO 80202

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OUTCROP | April 2019

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PRESIDENT’S LETTER By Tom Sperr

Geologists - Are We Scientists? organize an overview of where we have been. Geology is still a very descriptive field. Certainly, we use hard science. Big labs, full of people in white lab coats operate expensive machinery that spews out digits describing our rocks. But there is that word ‘describe’ again. Through the years, we travel writers seem to have moved from painting water color studies to

I have often wondered whether exploration geologists are really scientists. Many of you who know me would whole heartedly agree that I am not a scientist, but let’s leave that argument for another time. Much of my career has been that of a travel writer, describing the places visited in the subsurface and the inhabitants of this nether world; oil, gas and water. Like a travel writer, we visit a spot here and there and try to

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Lateral Thinking. Experience our Edge!

geostar energy partners

GeoStarSolu�ons.com OUTCROP | April 2019

303.249.9965 Vol. 68, No. 4 | www.rmag.org

RMAG/DWLS

Fall Symposium October 22, 2019

Call 4 Papers The Rocky Mountain Association of Geologists and the Denver Well Logging Society are teaming up again to present the 2019 Fall Symposium on October 22, 2019 at the Sheraton Denver West!

MULTISCALE IMAGING FOR RESERVOIR OPTIMIZATION

The technical program will be organized topically and will attempt to provide cross-disciplinary collaboration between our two societies. We welcome abstracts in the following categories: Imaging at nano, micro, and macro scales, Image analysis, 2-D and 3-D, Quantitative SEM imaging data and links to petrophysical measurements, Modeling properties: capabilities and limitations, Applications to reservoir characterization, conventional reservoirs, Applications to reservoir characterization, unconventional reservoirs, Applications to optimizing completions and production, including EOR, Dynamic imaging, and Future Directions We are especially interested in recent multidisciplinary reservoir studies, new interpretations of image analysis linked to production optimization and understanding, new play concepts and prospects based on application of image analysis and petrophysics, and new insights into conventional and unconventional petroleum systems in US basins. We welcome abstracts for the technical talks with a minimum of 500 words and up to a page. Send your abstract in today and join us for Multiscale Imaging for Reservoir Optimization, 2019!

Deadline for abstract submission is April 22nd, 2019 Authors of accepted abstracts have the option to submit a 4-10 page technical paper, with slides for course publication Send papers to: Katerina Yared kyared@sm-energy.com Vol. 68, No. 2 4 | www.rmag.org www.rmag.org

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President’s Letter

Solid Performance. Fluid Thinking.

can do the same thing. You can visit Cleveland and hypothesize what Toledo looks like. Your hypothesis would probably be right, too. They both would have the same gray, dreary weather much of the year, and a view of a big lake. Cleveland has the Indians while Toledo has the Mudhens. “The present is the key to the past” is the uniformist creed. But what do we really know about the geologic past? It seems like every day more geological studies are identifying catastrophic events in our rock record. How do you stack up and preserve fifty feet of Morrow sandstone in a single event? Do we ever see a volcanic eruption of the scale that occurred in the past in Yellowstone? I sincerely hope we don’t. Many geologists read mysteries, as do I. Our favorite detective will first gather clues from the scene of the crime. Many of the clues are not pertinent, if not darn right misleading. After sorting through the clues, the detective forms their hypothesis. Our sleuth then seeks other clues and interviews possible witnesses to get to the truth. This sounds like our jobs as explorationists. I guess that makes me Inspector Clouseau from the Pink Panther. But remember that even Clouseau occasionally solved his mystery. Good luck with all your ‘mysteries’.

making detailed photographs to describe our travels. A scientist is a person who employs the scientific method. One forms a hypothesis and dreams up experiments to test that hypothesis. Its very difficult to experiment with geology. If we had supernatural powers, we might create our own planet and turn loose a hurricane on a mountain sized pile of sand and

see what happens. Occasionally, mortals do perform experiments with the earth. We build dams that rupture and form interesting bedforms, or pump fluids into the earth near faults causing earthquakes. Not everyone approves of our experiments. Drilling a well is a form of an experiment where we hypothesize what lies in the subsurface and then drill to see if we are right. But really a travel writer

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LEAD STORY

The Colorado Mineral Belt Composite Batholith and its Role in Explaining the Genesis of Ore Deposits

FIGURE 1: Simplified map of the Colorado Mineral Belt (after Tweto and Sims, 1963),

highlighting some of the ore districts.

By Joshua M. Rosera1*, Sean P. Gaynor1,2 1: Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill NC 27599-3315 2: Department of Earth Sciences, University of Geneva, Geneva, 1205, Switzerland * corresponding author: roserajm@live.unc.edu

government formed the U.S. Geological Survey. One of the Survey’s early directives was to characterize and estimate the amount of mineral resources in Colorado. Consequently, the CMB became a focal point for the study of ore deposits. Many of the geological models used today for mineral exploration and characterization in continental settings are greatly influenced by early work completed in Colorado. In 1886, S.F. Emmons published a report detailing the geology and mineral resources of the prolific Leadville mining district. In his monograph, Emmons

INTRODUCTION The wealth of ore deposits in the Rocky Mountains of Colorado are largely concentrated into a narrow strip of land that extends from the Four Corners area to Boulder known as the Colorado Mineral Belt (CMB; Figs. 1 & 2). The mining districts throughout the CMB are of historical interest to the development of the state. Mining towns like Leadville had great economic influence, and the current metropolis along the Front Range owes much of its foundation to transporting ores extracted from the CMB. In 1879, three years after Colorado became a state, the federal

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LEAD STORY

FIGURE 2: Field photo looking north from the Middle Mountain molybdenum deposit near the historic mining town of Winfield, in

the central Colorado Mineral Belt. View is toward the Twin Lakes pluton, showing the close spatial association of unmineralized granites and mineral deposits, as well as the scale of igneous rocks within the central Colorado batholith. This region overlies a negative Bouguer gravity anomaly (see location on Fig. 4), which has led to the interpretation that deep, unexposed intrusions fed mineralizing fluids to deposits similar to that at Middle Mountain.

posited that the sediment-hosted ore bodies of the Leadville district were the result of deeply circulating meteoric waters that leached metals from rocks above. By turn of the 20th century, the field of economic geology had come to the realization that magmas, upon crystallization, release large amounts of water (and other volatiles), and that this process was crucial for explaining the origin of at least some ore deposits. This led Emmons to “resurvey” the Leadville district, and in 1907 he published a new interpretation of the Leadville district that discusses the role of magmatic waters derived from a deep-seated, and unexplored, magma system. Over the 100 years following the publication of Emmons & Irving (1907), numerous articles challenged the degree in which ore deposits form with significant components of magmatic fluid. This debate resulted in the reclassification of ore deposits to include those that are hydrothermal (having no appreciable evidence for magmatic fluid input) and those that are magmatic-hydrothermal (wherein some or all of the water is from a magma). Advances in the in analytical techniques and fields such as isotope geochemistry and geophysics would eventually be applied to help distinguish between deposits. In the CMB, isotopic studies demonstrate that

OUTCROP | April 2019

the prolific molybdenum deposits at Henderson and Climax formed by precipitation of ore directly from magmatic fluids (Stein and Hannah, 1985). Similar techniques applied to the carbonate hosted Pb-Ag-Zn deposits indicate varying degrees of magmatic input. A second line of evidence in support of the magmatic origin of many of the CMB deposits was through geophysical gravity data. Regional surveys discovered a large gravity low beneath the San Juan mountains and in the central CMB. It was hypothesized that this depletion in earth’s gravity potential was due to the presence of a buried, but upper crustal, low-density batholith. It is therefore envisioned that this deep batholith could have supplied large volumes of magmatic fluids to the overlying ore deposits in the CMB. We discuss herein why there is a gravity low in the central Colorado Rockies. First, we present basic models detailing how these gravity anomalies are believed to form. Then we discuss how economic geologists have used the inferred batholith in the central CMB to construct models to explain the origin of ore deposits. Although it is tempting to use some volume of the predicted batholith to justify the fluid budget for a given ore deposit, we show that such an approach is tenuous. Ultimately, we suggest more

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LEAD STORY

FIGURE 3: Schematic

models of Bouguer gravity anomalies (A) given a series of simplified low density blocks, showing the effect of different scales and depths of low density blocks on the Bouguer gravity anomaly (B-D). All examples (B-D) produce negative Bouguer gravity anomalies because the density of the schematic blocks is lower than their surrounding wall rock. The Bouguer anomaly corrects for topography, so all examples are shown with a horizontal surface.

can be used to determine the density structure of the crust, and the volumes of low or high density rocks buried in the subsurface. Negative Bouguer gravity anomalies, regions where the gravitational pull of the Earth is below the average gravitational field after terrain correction, are commonly interpreted as either the result of the presence of lower density rocks (e.g., sediments or felsic igneous rocks) or the lack of high-density crust (e.g., removal or delamination of high-density lower crust). The geometry and depth of these density contrasts directly affect Bouguer gravity anomaly (Fig. 3), so steep sided negative Bouguer gravity anomalies are commonly interpreted to be middle to upper crustal felsic batholiths. The CMB directly overlies a significant negative Bouguer gravity anomaly within Colorado, with the trend of ore deposits and surficial exposures of plutons oriented parallel to the major axis of the anomaly (Figs. 2 & 4). The magnitude of the anomaly has been interpreted to reflect a region of felsic intrusive rocks 8-25 km thick with a roof in the upper crust

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work is required to better understand how gravity data can be used to test hypotheses related to metal enrichments in Colorado and elsewhere.

BOUGUER GRAVITY ANOMALIES

The Earth is not a perfect, homogenous sphere, and variations in the mass of the crust locally alter the intensity of the Earth’s gravitational pull. Geologic features such as topography and high density or low density rocks all affect the local gravity through variations in the mass of the crust, and therefore create gravitational anomalies. By measuring acceleration using a gravimeter, researchers can determine the gravity at an individual point. After collecting these data at a high density over a large spatial area, it is then possible to determine anomalies in the local gravity field. One way to calculate gravity anomalies is using the Bouguer correction, which applies a terrain correction to remove the gravitational effects created by topography. Therefore, Bouguer gravity anomalies

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LEAD STORY

FIGURE 4: Bouguer gravity anomaly map of the CMB, highlighting the spatial association between the elongate negative

gravity anomaly and the surficial exposures of Cretaceous and younger granitic rocks of the central CMB. Gravity data from Oshetski and Kucks (2000).

(Isaacson and Smithson, 1976; McCoy et al., 2005). Due to the spatial proximity of CMB ore deposits to the buried batholith, researchers have long interpreted a genetic connection between the deep intrusions and shallow mineralization. This interpretation may have some significant assumptions in it however, as connecting unobserved, unstudied rocks to mineralization requires additional data to determine to what extent the buried batholith was involved with upper crustal mineralization.

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MAGMATIC-HYDROTHERMAL ORE DEPOSITS AND FLUID MASS BALANCE Fluids form in a magma when it depressurizes and/or when crystallization of anhydrous minerals occludes water and other volatiles. The fluids buoyantly rise to the roof of the magma body. The fluids leach metals either from their parent magma column, or from the wallrocks after they breach the magma’s contact. As the fluids circulate through

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fractures in the wallrock above and surrounding the intrusion, they cool and as a result, precipitate hydrothermal minerals. If enough metal-bearing fluid is focused into a relatively small area, a magmatic-hydrothermal ore deposit can form. Thus, the roofs of large intrusions make intriguing targets for mineral exploration because they can be the focus for huge volumes of magmatic-hydrothermal fluids (Fig. 5). If an independent determination of the volume of magmatic water needed to form a given ore deposit can be made, then it is possible to estimate the volume of magma from which the fluid was derived. For example, at the Climax molybdenum mine it has been estimated that a mineralizing fluid of 100 ppm Mo was extracted from a magma with 10 weight percent water, which would require approximately 125 km3 of magma to budget for all of the inferred Mo (Wallace et al., 1968). Lowering the water concentration to that of a more typical granite melt (~ 4 – 5 weight percent), or lowering the FIGURE 5: Magmatic-hydrothermal rock textures believed to be indicative of Mo concentration of the mineralizcrystallization during undercooling due to water saturation. Interpreted as fluiding fluids increases the magmatic rich plumes and often found near the roof of an intrusion (Shannon et al., 1982;). volume required. Wallace and BookSample from Henderson molybdenum mine (note, quartz-molybdenite veins). strom (1993) revised the estimated volume of parental magma at Climax CONNECTING GEOPHYSICAL AND to more than 400 km3. The volume of magmatic fluid PETROLOGIC OBSERVATIONS involved in ore formation can also be estimated with The identification of a large gravity low and its stable oxygen isotope studies. In the Leadville disinterpretation as a buried mass of intrusive rocks trict, it is estimated that 4 km3 of mineralizing water 3 beneath the CMB opens up the possibility of formuwas extracted from a deep-seated 640 km magma lating ore deposit models that can tap large-volume chamber (Thompson and Beaty, 1990). These mass magmatic bodies. In numerous instances, the presbalance estimates require relatively large volumes of intrusive magma that are actively crystallizing at the ence of the inferred batholith beneath the CMB has CONTINUED ON PAGE 26 time of ore formation.

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LEAD STORY part in mineralization at the Questa deposit. High-precision geochronological data comparable to that at Questa (Gaynor et al., 2018) for the CMB are sparse. Where available, measured ages of plutons in the CMB suggest they formed incrementally. The Twin Lakes pluton, which is located near the deepest portion of the CMB gravity low, was assembled between 63 – 57 Ma and 43 – 40 Ma (U-Pb zircon ages; Feldman, 2010). The Middle Mountain molybdenum deposit (Fig. 4) cuts the Twin Lakes pluton. Most of the pluton is therefore pre-mineral, and much of the deep gravity low in this location was assembled piecewise over at least 7 Ma before mineralization. The ~35 Ma Mount Princeton batholith is associated with numerous small ore deposits. However, recent high-precision zircon geochronology demonstrate it amalgamated slowly over ~ 500 ka, with the oldest rocks near the roof of the batholith (Mills and Coleman, 2013). It is unlikely the whole volume of the Mount Princeton batholith ever existed as a melt-rich magma body from which large volume of fluids could have been extracted.

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been used to justify mass balance estimates. However, we have no ability to date a Bouguer gravity anomaly, so it is typically assumed that the modeled volume of batholith beneath a given ore body was magma at the time of mineralization. Over the last decade and a half, petrologic research has determined that plutonic assembly is an incremental process, with plutons and batholiths forming through the piecemeal addition of discrete magma batches (e.g., Coleman et al., 2004). Due to the relatively cool thermal conditions of the middle and upper crust, magmas rapidly crystallize upon emplacement. Although individual batches of magma may amalgamate to build a single, chemically similar intrusive body, it is insufficient to assume a given pluton or batholith ever existed as a large, liquid magma body comparable in volume to its final crystallized size (e.g., Annen, 2009). Consequently, Bouguer gravity data do indicate there are large buried volumes of relatively low-density intrusive rocks within the CMB, but their mere presence does not necessitate a genetic association between the full batholith and individual ore deposits. This problem was recently addressed by Gaynor et al. (2018) in northern New Mexico. There, the Questa molybdenum deposit, which is similar to the deposits at Climax and Henderson, lies in the middle of a regional Bouguer gravity low. Detailed geochronology combined with intrusive volume estimates indicate that most of the granitic rocks within the Questa Bouguer low were emplaced 1 – 5 million years after Mo mineralization; they could not take

WHAT NEXT?

As alluded to by Emmons and Irving (1907), the role of magmatism in forming ore deposits at Leadville, and the CMB as a whole, is hard to ignore. However, problems still remain with linking magmatism to mineralization. In particular, accounting for the large mass of fluid focusing required to form an ore deposit remains critical for understanding

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LEAD STORY Geophysical Monograph, American Geophysical Union, The Rocky Mountain Region- An evolving Lithosphere: Tectonics, Geochemistry, and Geophysics, v. 154, p.99-106. Mills, R. D., Coleman, D. S., 2013, Temporal and chemical connections between plutons and ignimbrites from the Mount Princeton magmatic center: Contributions to Mineralogy and Petrology, v. 165, p. 961–980, doi:10.1007/ s00410-012-0843-4. Oshetski, K. C., Kucks, R. P., 2000, Colorado aeromagnetic and gravity maps and data: a web site for distribution of data: USGS Open-File Report, 00-0042, http://greenwood.cr.usgs.gov/pub/ open-file-reports/ofr-00-0042/colorado.html Shannon, J. R., Walker, B. M., Carten, R. B., Geraghty, E. P., 1982, Unidirectional solidification textures and their significance at the Henderson Mine, Colorado: Geology, v. 10, p. 293-297. Stein, H. J., Hannah, J. L., 1985, Movement and origin of ore fluids in Climax-type systems: Geology, v. 13, p. 469-474. Thompson, T. B., Beaty, D. W., 1990, Geology and the origin of ore deposits in the Leadville district Colorado: Part II. Oxygen, hydrogen, carbon, sulfur, and lead isotope data, and development of a genetic model. Economic Geology Monographs, v. 7, p. 156–179. Tweto, O., Sims, P. K., 1963, Precambrian ancestry of the Colorado Mineral Belt, Geological Society of America Bulletin, v. 74, p. 991 – 1014. Wallace, A. R., 1995, Isotopic geochronology of the Leadville 1° x 2° quadrangle, west-central Colorado – Summary and discussion: U.S. Geological Survey Bulletin 2104, 51 p. Wallace, S. R., Bookstrom, A. A., 1993, The Climax porphyry molybdenum system: Colorado School of Mines Quarterly, v. 93, no. 1, p. 35 – 41. Wallace, S. R., Muncaster, N. K., Jonson, D. C., Mackenzie, W. B., Bookstrom, A. A., Surface, V. E., 1968, Multiple intrusion and mineralization at Climax, Colorado, in Ore Deposits of the United States, 1933 - 1967, New York, The American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., v. 1, p. 605–640.

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these geologic systems. Age discrepancies similar to those described above for the Twin Lakes pluton and Mount Princeton batholith likely exist throughout the CMB, but most of the existing geochronology was gathered with lower precision chronometers that are prone to thermal perturbations (e.g., K-Ar, zircon fission track; Wallace, 1995). Future research should use more robust geochronometers to continue exploring the intrusive history of the CMB to better estimate what portion of the inferred batholith can be used for fluid mass balance of a given deposit location at a given time. Such data would strengthen magmatic-hydrothermal deposit models, and build into a rich history of geologic research in the Colorado Rockies.

REFERENCES

Annen, C., 2009, From plutons to magma chambers: thermal constraints on the accumulation of eruptible silicic magma in the upper crust: Earth & Planetary Scientific Letters, v. 284, p. 409-416. Coleman, D. S., Gray, W., Glazner, A. F., 2004, Rethinking the emplacement and evolution of zoned plutons: Geochronologic evidence for incremental assembly of the Tuolumne Intrusive Suite, California: Geology, v. 32, p. 433-436. Emmons, S. F., Irving, J. D., 1907, The Downtown District of Leadville, Colorado: USGS Bulletin 320. Feldman, J. D., 2010, The emplacement and exhumation history of the Twin Lakes batholith and implications for the Laramide orogeny and flat slab subduction [MSc Thesis]: New Mexico Institute of Mining and Technology, 185 p. Gaynor, S. P., Coleman, D. S., Rosera, J. M., Tappa, M. J., 2018, Geochronology of a Bouguer Gravity Low: Journal of Geophysical Research Solid Earth, doi: 10.1029/2018JB015923. Isaacson, L. B., Smithson, S. B., 1976, Gravity anomalies and granite emplacement in west-central Colorado: Geological Society of America Bulletin, v. 87, p. 22-28. McCoy, A. M., Roy, M., Leandro, T., Keller, G. R., 2005, Gravity modeling of the Colorado Mineral Belt, in: Karlstrom, K. E. & Keller, G.R. (eds) OUTCROP | April 2019

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RMAG LUNCHEON PROGRAMS Speaker: Lisa Morgan | April 3, 2019

The Hydrothermal System Beneath Yellowstone Lake (and why it’s so important to map lakes in Yellowstone) Lisa Morgan one third; tectonism has affected the entire lake basin. Mapping in the northern lake basin has identified a dynamic lake floor with active faults, active and inactive hydrothermal vent craters, hydrothermal domes, large hydrothermal explosion craters, extensive rhyolitic lava flows, land slide deposits in an area with very high seismicity and heat flow values. The vent fields on the floor of Yellowstone Lake represent the third largest thermal basin in Yellowstone, the largest continental hydrothermal system on Earth. Our current project, Hydrothermal Dynamics of Yellowstone Lake (hdylake.org),

Yellowstone Lake lies above the active Yellowstone hot spot, a region strongly affected by young (<2.1 million year) silicic volcanism, active tectonism, and accompanying uplift. Yellowstone Lake is the largest (surface area of 341 km2), high altitude (>7000 feet in elevation) lake in North America and straddles the southeast margin of the 630,000-year Yellowstone Caldera, one the world’s largest active silicic volcanoes. Previous high-resolution bathymetric mapping reveals a lake floor dominated by volcanic and hydrothermal processes in the northern two-thirds of the lake and by fluvial and glacial processes in the southern

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Call for Papers RMAG and DWLS are gearing up for our annual Fall Symposium. The Call for Papers has been posted! The theme is “Multiscale Imaging for Reservoir Optimization.”

Click here for more information and to find out how to submit your paper.

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Vol. 68, No. 4 | www.rmag.org

RMAG LUNCHEON PROGRAMS The instruments monitored the flow and chemistry and temperature of fluids from deep in the subsurface and how that flow was affected by high seismicity (Yellowstone averages 3000 small earthquakes annually), and seasonal changes in lake level. Preliminary results of analyses of over 100 m of sediment core from the northern basin of Yellowstone Lake with additional cores from West Thumb basin and nearby lakes provide an improved perspective regarding postglacial climate and indicate that hydrothermal activity on the lake floor has been active at least since the last glaciers receded from the basin. The HD-YLake project has afforded researchers the opportunity to examine and better understand subsurface processes in a very active and dynamic environment that few have been able to observe.

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funded by the National Science Foundation and supported by the U.S. Geological Survey, Woods Hole Oceanographic Institute, The Global Foundation for Ocean Exploration, and Yellowstone National Park, seeks to understand the relationship between seismicity, hydrothermal activity on the lake floor, and seasonal lake level changes as well as the past 15,000-year climate and geologic history of the northern lake basin. Our field strategy used a two-pronged approach: geophysical and geochemical monitoring of the active system, and analyses of 14+ lake sediment cores. Over a period of two years, geophysical and geochemical instruments were deployed in the deepest part of Yellowstone Lake in a 200-m-wide active hydrothermal vent field for one-year increments.

LISA MORGAN is scientist emeritus for the U.S. Geological Survey, whose focus is on the geology and geophysics of volcanic terrains. With co-author Ken Pierce, Morgan developed major concepts and a model for development of the track of the Yellowstone hot spot, documenting the northeastward spatial and temporal progression of volcanism, faulting, and uplift along the 17-Ma Snake River Plain-Yellowstone Plateau volcanic province. From 1999-2004, Morgan with colleagues mapped the floor of Yellowstone Lake becoming the first to recognize the complex geology present and active on the floor of Yellowstone Lake. Processes such as hydrothermal explosions, emplacement of rhyolitic lava flows, landslides, extensive hydrothermal vent fields, and

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active faulting contribute to the geologic framework of the lake. Presently, her research with the Yellowstone Volcano Observatory on the Yellowstone Plateau focuses on the geology and associated hazards in Yellowstone Lake, physical processes associated with eruption of the post-glacial (<15 ka), large (>100 m diameter) hydrothermal explosion craters, the physical characteristics associated with emplacement of the 0.63-Ma Lava Creek Tuff and development of the Yellowstone caldera, and emplacement of post-caldera rhyolitic lava and pyroclastic flows on the Central Plateau. Currently, Morgan and colleagues at multiple institutions are examining the relationships between seismicity, fluid chemistry, and active hydrothermal vents on the lake floor

and how those processes are affected by seasonal changes in lake level. Our project, Hydrothermal Dynamics of Yellowstone Lake (hdylake.org), uses a two-pronged approach: geophysical and geochemical monitoring of the active system and analyses of sediment cores to study the postglacial (~15,000-year) history of hydrothermal activity beneath the lake. Morgan has a Ph.D. in Geology and Geophysics from the University of Hawaii where she specialized in physical volcanology. She has a M.S. in Geology from the University of Colorado with an emphasis on volcanic stratigraphy, petrology, and rock magnetics. Her B.S. is in Geology from the University of Missouri at Kansas City with minors in Mathematics and Philosophy.

OUTCROP | April 2019

RMAG LUNCHEON PROGRAMS Speaker: Bob Raynolds | May 1, 2019

Stratigraphic controls on hydrocarbon systems in Colorado By Bob Raynolds

BOB RAYNOLDS obtained his PhD at Dartmouth College working on the Siwalik sediments of Pakistan. He has taught University, worked forÂ the USGS, Exxon and Amoco, and is Adjunct at Colorado School of Mines and Stony Brook University. His current research interests are the Turkana Basin of Kenya, the Denver

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our State being tied to this interval. Older hydrocarbon systems are in the Ancestral Rockies basins (such as the Eagle and Paradox basins) and in the Paleozoic shelf margin strata. Some hydrocarbon systems have been breached and exist today only as stained vestiges of former reservoirs, there are examples in the Paleozoic Eagle Basin and Mesozoic Front Range strata. This presentation will use new digital stratigraphic charts and resource compilations to illustrate regional patterns that apply to Colorado as well as to adjacent states. Recognizing genetic patterns and processes controlling facies distribution patterns encourage the use of exploration models that start with evaluation of rock volume and organic concentration leading to play prioritization.

The geology of Colorado can be considered in 8 chapters characterized by common themes of erosion, deposition, and lithofacies distribution. An analysis of these chapters from the standpoint of source rock distribution and organic material concentration allows us to characterize stratigraphic factors controlling the distribution and occurrence of oil, gas, and coal in Colorado. As we break Coloradoâ&#x20AC;&#x2122;s stratigraphic record into a series of depositional episodes (deposodes per Galloway), is becomes evident that broad patterns of subsidence and sediment supply have controlled the distribution of source, reservoir and seal rocks through time. The principal hydrocarbon engine is in the Cretaceous Interior Seaway with the majority of hydrocarbons that have been produced from

Basin, and the use of paleogeographic reconstructions to understand and predict facies distribution patterns. KATHY ROBINSON: Before becoming a geologist and educator, Kathy worked as a research analyst in the energy industry, focusing on operational and developing power, gas, and coal infrastructure in

North America. She earned her B.S. in Applied Geology from Metropolitan State University of Denver, and she holds a college teaching certificate and M.S. in Geology from University of Colorado Boulder where she specialized in thermochronology method development. She is currently early in her career as a college instructor of geoscience.

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MINERAL OF THE QUARTER By Jamison Brizendine1 and Ronald L. Parker2 1: Takeoff Technician, Independence Excavating, Inc., 5720 E. Schaaf Rd., Independence, Ohio, 44131 2: Senior Geologist, Borehole Image Specialists, 5650 Greenwood Plaza Boulevard, Suite 142, Greenwood Village, CO 80111

RHODOCHROSITE The Red Jewel of the Rockies

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MINERAL OF THE QUARTER: RHODOCHROSITE who discovered the bright pinkred mineral in the polymetallic mines in Romania. He named the mineral rhodochrosite after the Greek word, rhodon (rose-colored). Rhodochrosite is sometimes confused with rhodonite, a manganese silicate, although they are easily discriminated by hardness. Rhodochrosite is softer with a Moh’s hardness of 3.5 to 4, compared to a Moh’s 6 for rhodonite (Johnson, 2002). Well-crystallized rhodochrosite commonly appears as euhedral rhombohedra - form {10‾11}. (Johnson, 2002). These crystals display a 3-sided perfect cleavage, similar to the

Rhodochrosite is a mineral that is hard not to notice. Although it is not a common mineral, rhodochrosite is known from worldwide occurrence. Most commonly, it occurs as an opaque, pinkish massive material associated with other minerals that have attracted the attention of miners. Early in the mining history of the Rocky Mountains, rhodochrosite was classified as a gangue mineral, and so, was discarded as waste from mines seeking different treasure: mostly gold and silver. As noted by Eckel et. al. (1997), “…rhodochrosite occasionally develops into remarkable pink to deep red crystals that are among the finest in the world”

(p. 407). Indeed, it is these types of rhodochrosite that make it the desire of mineral collectors and museums (Muntyan, 2000). Rhodochrosite was named the “State Mineral of Colorado” in 2002 because the best rhodochrosites in the world hail from the Centennial State and John Ghist’s Earth Science class at Platte Canyon High School learned that Colorado did not previously have a state mineral (Murphy and Modreski, 2002). Rhodochrosite is manganese carbonate (MnCO3) that forms in a variety of geologic environments. The mineral was first named in 1813 by geologist Johann Friedrich Hausmann,

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On Left: The “Alma King” is a deep cherry-red, single rhombohedron that is the largest complete rhodochrosite crystal known to humanity. The Alma King is “considered by some mineral curators to be the best non-gem mineral specimen in the world.” (Paty, 2001). In 2007 this specimen was valued at more than 1 million dollars. It was discovered by Bryan Lees in a vug named the “Rainbow Pocket” in the Sweet Home mine, Alma District, Park County, Colorado on August 21st, 1992. A movie camera recorded the discovery. The Alma King is 14 cm x 16.5 cm and is surrounded by pocket matrix minerals quartz, fluorite, tetrahedrite, sphalerite and huebnerite. The Alma King is on permanent display at the entrance to the Coors Mineral Hall at the Denver Museum of Nature and Science. Photo by Ronald L. Parker Vol. 68, No. 4 | www.rmag.org

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MINERAL OF THE QUARTER: RHODOCHROSITE

A mixture of rhodochrosite, acicular quartz, chalcopyrite and sphalerite from the Sweet Home Mine, Alma, Park County, CO. On display at the Denver Museum of Nature and Science. Photo by Ronald L. Parker. rhombohedral cleavage seen in calcite spar (which is also on {10‾11}). Low hardness and ready cleavage make rhodochrosite impractical as everyday jewelry, but beautiful museum display gemstones have resulted from careful faceting and polishing. Twinning can occur as lamellar twins on {101‾2}, though it is rare (Deer et al., 1992; Sittinger et al., 2004). As with many carbonate minerals, rhodochrosite effervesces with dilute HCl. Rhodochrosite belongs to the special type of hexagonal crystals known as the trigonal crystal system, (bar32/m) – Hexagonal Scalenohedron. Rhodochrosite can be found as individual rhombohedral and scalenohedral crystals as well as botryoidal layered masses and granular surface coatings. Rhodochrosite is isostructural with calcite (CaCO3) and siderite (FeCO3). Although

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rhodochrosite is most often close to end-member MnCO3, specimens often contain Ca2+ or Fe2+. The mineral forms a complete solid solution series with calcite (Ca substituting for Mn, i.e. manganocalcite) and siderite (Fe substituting for Mn, i.e. manganosiderite). Rhodochrosite specimens from the Poudrette (Demix) Quarry, Mount Saint-Hilaire, Quebec, Canada are brownish because of isomorphic substitution of Fe2+ for Mn2+. In some cases, a thin black layer of manganese oxides and oxyhydroxides forms an alteration coating along cleavage planes or on external surfaces (Deer et al., 1992; Cook, 1993). Rhodochrosite forms in a variety of geologic environments. These include sedimentary rhodochrosite that forms in low-temperature laminated sediments, concretionary aggregates or in manganiferous iron deposits (Klein and Philpotts, 2013). Saunders and Swann (1992) describe laminated,

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MINERAL OF THE QUARTER: RHODOCHROSITE

The cascading wall of rhodochrosites from the crystal cavity reconstruction of the Sweet Home Mine on display at the Denver Museum of Nature and Science. The history of the discovery and curation of this massive mineral specimen is described by Murphy (1997). Width of view ~4 feet. Photo by Ronald L. Parker.

botryoidal rhodochrosite, siderite and pyrite that form cementing phases in fractured cherts of the Paleozoic aquifer in northeast Mississippi. Rhodochrosite and the other minerals form by strongly reducing conditions that mobilize Mn2+ and Fe2+, attended by limestone dissolution and sulfate reduction. Alternating bands of rhodochrosite and siderite indicate fluctuating redox conditions. The paucity of similar findings elsewhere suggests that these geochemical conditions are unusual (Saunders and Swann, 1992). Polgari, et. al., (2013), describe the geochemical origins of fish-bearing rhodochrosite concretions from Jurassic manganese deposits of the Transdanubian Range in Central Europe. Their two-phase model requires an initial accumulation of manganese proto-ore in sediment by enzymatic

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oxidation of dissolved Mn2+. Then, reduction of the manganese proto-ore was catalyzed by anaerobic methane oxidation via sulfate-reducing bacteria to yield reactive carbonate. This geochemical mechanism has explained anomalous concretion growth in other marine shales (Lash and Blood, 2004). In igneous terrane, rhodochrosite forms as metasomatic alteration of primary sulfidic ore deposits, as hydrothermal fracture-filling vein-fills, and as pegmatite material (Guilbert and Park, 2007; Logan, 2013). At Gilman, Colorado, rhodochrosite is the result of contact metamorphism (Muntyan, 2002). Typical association minerals include pyrite, silver, chalcopyrite, bornite, galena, quartz, fluorite, sphalerite, tetrahedrite, gypsum, calcite and huebnerite (Muntyan, 2002).

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MINERAL OF THE QUARTER: RHODOCHROSITE

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Before the Second World War, mines that produced distinct rhodochrosite crystals were rare. At the type locality, Cavnic, Romania, rhodochrosite was found as small rosettes and at the Wolf Mine, Siegerland, Germany, it was found as small scalenohedral crystals. In fact, early mineral textbooks such as Edward S. Dana’s System of Mineralogy (1920) and Mineralogy by Henry A. Miers (1902) stated that distinct crystals of rhodochrosite were uncommon and not well crystallized. The situation changed when the mines in the United States, Banded laminations of stalactitic rhodochrosite formed by post-mining drainage of Mn-bearing Argentina, Bulgaria, Canwaters through old silver mines, Capillitas, Catamarca Province, Argentina. 7 cm x 6 cm. Photo by ada, Mexico and South AfRonald L. Parker rica were found to contain polymetallic ores, and time (Jones, 2004). those rich in manganese often yielded rhodochroSilver mines from numerous localities in the Pesite. Recent mining in Peru, Kosovo, and China have ruvian Andes have been worked from Incan times. also produced outstanding examples of the mineral Recently, these mines have yielded quality rhodo(Jaroslav and Hyrsl, 2004; Logan, 2013). Today there chrosite specimens. The Uchucchacua Mine, Lima are hundreds of recorded localities that produce Department, rhodochrosite was found as small scawell-crystallized rhodochrosite. Several notable lolenohedral crystals with silver and other mangacalities are discussed below. nese minerals. At the Huayllapon Mine in Pasto BueIn the Capillitas mining district in Catamarca, Arno, Ancash Department, and at the Manuelita Mine, gentina, rhodochrosite was found in banded massJunin Department, excellent rhombohedral rhodoes and stalactites in caves. Instead of calcium-enchrosite with associated quartz and pyrite were reriched solutions that typically form stalactites, the covered (Sittinger et al., 2004). ones forming Argentina’s cave decorations were Another recent manganese deposit that has proenriched with manganese, making them pink to a duced world-class rhodochrosite specimens is the deep-red. Miners and lapidary artists have harvestWutong Mine, Liubao, Cangwu County, Guangxi Preed the stalactites to be sliced cross-wise as specimens or to be polished and shaped into cabochons fecture, China. This mine produced a variety of haband spheres. After polishing, these specimens disits of rhodochrosite including: flattened, twinned play opaque bands and concentric growth patterns crystals up to 8 cm; large, bladed crystals up to 16 that record successive growth of layers outward over CONTINUED ON PAGE 40

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MINERAL OF THE QUARTER: RHODOCHROSITE

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cm across; and highly flattened, discoidal crystals up to 6 cm across. Some notable specimens from the Wutong Mine include the “Emperor of China” (a 40 cm x 60 cm specimen with a crystal exceeding 20 cm!), the “Empress of China” and “The Lips”. The variety of crystal habits of rhodochrosite found here is likely due to rapid crystal growth (Lees et al., 2011). Rhodochrosite found in the Kalahari Manganese Fields of South Africa is unique. Mines near Kuruman and Hotazel (named for the harsh Kalahari climate) produce unusual specimens. In 1977, the N’Chwaning I Mine yielded a zone of Rhodochrosite rosettes on quartz from the type locality, Cavnic, Maramures County, Romania. deep red, gemmy, scaleCarnegie Museum of Natural History specimen CM 27836. 12 cm x 1.6 cm x 1.2 cm. Photo by nohedral crystals to 7 cm. Jamison Brizendine. One of the best specimens was a 16 cm x 14 cm plate specimens were those produced in the late 1800s of glowing red. A few thousand specimens were refrom the Emma and Leonard mines in Butte, Silver covered; many more were damaged (Cairncross et Bow County, Montana. The rhodochrosite from Butte al., 2013). Three other habits of less intensely colwas a pale pink color and was often found with pyored rhodochrosite were also found: “wheat-sheaf” rite, enargite and covellite. In the early 1900s, Colobundles of elongated crystals in parallel clusters rado started producing ore rich in lead, manganese, (some opaque in the center with transparent termiiron and more importantly, silver and gold (Guilbert nations); second-generation overgrowths with flat and Park, 2007; Jones, 2007). Early Colorado rhodoterminations; and opaque, pink hemispheres—the chrosite specimens came from the Mosquito Range best perched on top of a contrasting black, mangain a suite of old silver mines. Excellent deep red nite-rich matrix (Wilson, 2014). Finding an undamrhodochrosite specimens were recovered from the aged rhodochrosite from the Kalahari Desert on the John C. Reed Mine, the Mary Murphy Mine, the Grizmarket is a real challenge. Top quality specimens zly Bear Mine, and the Climax Mine. These Colorado vie with those from the Sweet Home Mine in Coloraspecimens were never abundantly available to mindo for a claim as the best in the world (Jones, 2004; eral collectors and remain rare (Muntyan, 2011). Jones, 2007; Logan, 2013). In the early 1960s, Standard Metals Co. acquired In the United States, the first rhodochrosite CONTINUED ON PAGE 42

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the old Sunnyside Mine near Silverton in San Juan County to mine gold. An existing tunnel in the Gold King Mine, near Gladstone, called “The American Tunnel”, was expanded to intersect the Sunnyside Mines older workings. The upper levels of the Sunnyside Mine produced vugs containing an abundance of milky quartz, green fluorite and pink rhodochrosite as excellent combination specimens. Older specimen labels from the Sunnyside Mine often cite “Silverton”, “American Tunnel” or “Gladstone” as the locality (Jones, 2007; Muntyan, 2011; Murphy, 2011). The premier Earth locality for rhodochrosite is the Sweet Home Mine in the Alma District, Park County, Colorado. Initially mined for silver, starting in 1873, the Sweet Home Mine has yielded what are arguably the best rhodochrosites so far known. According to Bartos, “Some of these specimens are considered to be among the finest mineral Botryoidal rhodochrosite: from the Manuelita Mine, Morococha District, Yauli specimens ever produced and the finest Province, Junin Department, Peru, 3.8 cm x 4.4 cm x 4.3 cm, Jamison Brizendine of their species with values well over specimen (JKB 2047). Photo by Jamison Brizendine. $1 million US dollars” (Bartos, 2007, p. 235). At the Sweet Home Mine, the headed by Bryan Lees, president of Collector’s Edge, unique geological conditions that favored the propurchased the Sweet Home Mine and began a seriduction of such high-quality crystals are a relativeous campaign to map and mine targeted areas for ly small, relatively shallow (1.5 – 2.5 km deep) pulse rhodochrosite. During the 1990s, Collector’s Edge of magmatic invasion that then cooled slowly withdiscovered many productive pockets at the Sweet in the reach of groundwater circulation. Sweet Home Home Mine that were affectionately named, e.g., veins were higher temperature and higher saliniCorner Pocket, Good Luck Pocket, Hard Luck Pockty than other rhodochrosite-forming systems which et, Cash Flow Pocket, Hedgehog Pocket, Rainbow contributed to pure MnCO3 mineralization and Pocket, Blue Moon Pocket, Blueberry Pocket and Nathe deep cherry-red color (Wenrich, 1998; Bartos, te’s Pocket (Muntyan, 2002). These typically narrow 2007). Vein formation included quartz, sphalerite, pockets produced rhodochrosite of good red color tetrahedrite, and fluorite along with an abundance of intimately associated with white quartz, purple fluless-common minerals (Bartos, 2007). Between the 1960s and 1991, various owners orite, tetrahedrite and chalcopyrite. All of the rhodotried their hand at mining rhodochrosite from the chrosite crystals from this location display a rhomSweet Home Mine. The “Alma Queen”, discovered in bic habit with some crystals nearing 7.5 cm on an 1965, was the only famous specimen found (Voynick, edge. Some of the gemmy, but broken, material has 1998; Logan, 2013). In 1991, a group of investors, CONTINUED ON PAGE 43

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been faceted and mounted as jewelry. The discovery of the “Alma King” is unique in that it was filmed as it happened. Dave Baysinger, the manager of the Denver Museum of Nature and Science’s video department, was on hand as Bryan Lees unearthed the “Alma King”. The 12.5 cm specimen, is now on permanent display at the entrance to the Coors Hall of Minerals at the Denver Museum of Nature and Science (Murphy, 1997). After the “Alma King” was found, another impressive specimen was recovered which had four, 7.5 cm crystals with associated Scalenohedral (dog-tooth) rhodochrosite on manganite (MnO(OH) from the N’Chwaning I Mine, stilbite and quartz. This Kuruman, Kalahari Manganese Field, Northern Cape Province, South Africa. 11.5 cm x 11 cm x 3 specimen was called the cm. Carnegie Museum of Natural History specimen (CM 18921). Photo by Jamison Brizendine. “Alma Rose” and can be seen at the Rice Museum of Rocks and Minerals in minerals were delicately removed, protected and Hillsboro, Oregon (Moore, brought to the laboratory. Repeated chemical baths, 1998; Jones, 2007; Logan, 2013). Other notable rhoover a 6-month span, removed iron oxide staining. dochrosite specimens from the Sweet Home Mine include “Big Red”, “Big Red’s Brother”, “Snow-Cone” Then the wall was painstakingly rebuilt. The 750 and the “Searchlight”. pound wall took 14 months to reconstruct (Murphy, One of the most impressive discoveries at the 1997). The “rhodochrosite wall” can now be seen in Sweet Home Mine occurred in September of 1994, the Denver Museum of Nature and Science (Moore, when miners opened a seam of rhodochrosite that 1998; Jones, 2007). extended nearly 2 m high and almost 2.7 m across. With the abundance of localities that have now This seam was festooned with hundreds of 2.5 cm produced fine rhodochrosite specimens, it can be to 5.0 cm crystals of intense, cherry-red rhodochrosaid with confidence that both Edward Salisbury site along with quartz, purple fluorites, pyrites tetDana and Henry Miers were proven incorrect! Alrahedrites and sphalerites (Murphy, 1997). Collecthough it takes a bit of searching at mineral shows, tor’s Edge decided to try to preserve the entire seam, a collector can usually find a few specimens of this rather than trimming it down to make multiple specpink mineral from a variety of world localities. Rhoimens. This was a daunting task as the wall was lodochrosite: A true mineral jewel! cated 1000’ underground. Fragments and individual CONTINUED ON PAGE 44

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MINERAL OF THE QUARTER: RHODOCHROSITE Guilbert, John M., and Park, Charles F., 2007, The Geology of Ore Deposits: Waveland Press, Inc., Long Grove, Illinois, Second edition: p. 219, 407 Johnsen, Ole, 2002, Minerals of the World: Princeton University Press, Princeton, N.J. 439 pp. Jones, Bob, 2004, The Frugal Collector: The Other Carbonates: Part I: The Copperless Carbonates: Rock and Gem, 34(12):20-22, 24-25, 98. Jones, Bob, 2007, Royal Rhodochrosite: This Plentiful Species is Anything but Common: Rock and Gem, 37(7): 20-25. Klein, Cornelis and Philpotts, Anthony, 2013, Earth Materials – Introduction to Mineralogy and Petrology: New York: Cambridge University Press, 536 pp. Lash, Gary and David R. Blood, 2004, Geochemical and Textural Evidence for Early (Shallow) Diagenetic Growth of Stratigraphically Confined Carbonate Concretions, Upper Devonian Rhinestreet Shale, Western New York, Chemical Geology, 206 (3-4): 407-424. Lees, Bryan K., Behling, Steven C., Misantoni, Dean, Luders, Volker, Romer, Rolf L., Sanchez, Pilar L., and Cory, Paul, 2011, The Wutong Mine, Guangxi Zhuang Autonomous Region, China: The Mineralogical Record, China III, 42(6): 521-544. Logan, William, S., 2013, Rhodochrosite: Crystals of Drama and Nuance. Spectrum Minerals and Blurb, Inc. Publishing, Charlotte, North Carolina: 159 p. Miers, Henry A., 1902, Mineralogy: An Introduction to the Scientific Study of Minerals: MacMillan and Co., LTD., New York, New York: p. 404. Moore, Thomas P., 1998, New Operations at the Sweet Home Mine, 1990-1997: The Mineralogical Record, 29(4): 21-100. Muntyan, Barbara L., Colorado Rhodochrosite, Rocks & Minerals, 75(5): 302-316. Muntyan, Barbara L., 2011, Rhodochrosite from the San Juans in The San Juan Triangle of Colorado - Mountains of Minerals: Lithographie, LLC., Denver, Colorado, Mineral Monograph no. 15, pp. 60-67. Murphy, Jack A., 1997, Sweet Home Mine

»»CONTINUED FROM PAGE 43 WEBLINKS https://collectorsedge.com/pages/the-wutong-rhodochrosite-mine-guangxi-zhuang-autonomous-region-china. https://collectorsedge.com/pages/ sweet-home-mine-park-county-colorado-usa, https://collectorsedge.com/pages/ sweet-home-mine-alma-park-county-colorado-2 https://www.mindat.org/min-3406.htm http://www.newyorkmineralogicalclub.org/history/2005-GemMineralAlmanac.pdf http://webmineral.com/data/Rhodochrosite.shtml#.XJA_4ShKiHs

REFERENCES Bartos, Paul J., Eric P. Nelson and Dean Misantoni, 2007, The Sweet Home Rhodochrosite Specimen Mine, Alma District, Central Colorado: the Porphyry Molybdenum-Fluorine Connection, Mineralium Deposita 42(3): 235-250. Bernard, Jan B., and Hyrsl, Jaroslav, 2004, Minerals and their Localities: Granit, S.R.O., Prague, Czech Republic: p. 511-512. Cairncross, Bruce and Beukes, Nicolas J., 2013, The Kalahari Manganese Field: The Adventure Continues: Struik Nature Publishing, Cape Town, South Africa: p. 297-315. Cook, Robert B., 1993, Connoisseur’s Choice: Rhodochrosite, Alma, Park County, Colorado: Rocks and Minerals, 68(1): 40-43. Dana, Edward S., 1920, The System of Mineralogy of James Dwight Dana, 1837-1868, Descriptive Mineralogy: John Wiley & Sons, Inc., New York, New York, Sixth edition: p. 278-279. Deer, William A., Howie, Robert A., and Zussman, Jack, 1996, An introduction to the rock forming minerals: Pearson-Prentice Hall, Harlow, Essex, England, United Kingdom, Second edition: p. 635-637. Eckel, Edwin B., Robert R. Cobban, Donley S. Collins, Eugene E. Foord, Daniel E. Like, Peter J. Modreski and Jack A. Murphy, 1997, The Minerals of Colorado, Revised and Updated. Golden, Colorado: Fulcrum Publishing. 665 pp. OUTCROP | April 2019

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Rhodochrosite, Fluorite and Quartz for the Sweet Home Mine, Alma District, Park County, Colorado, United States, 4 cm x 3 cm x 1 cm, Jamison Brizendine specimen (JKB 240). Photo by Jamison Brizendine. Environmental Sciences, 8(4): 139-146. Saunders, James A. and Charles T. Swann, 1992, Nature and Origin of Authigenic Rhodochrosite and Siderite from the Paleozoic Aquifer, Northeast Mississippi, U.S.A., Applied Geochemistry, 7(4):375-387l Sittinger, Richard, Sittinger, Cheryl, and Voynick, Steve, 2004, Mineral of the Month: Rhodochrosite: Mineral of the Month club, June 2004: 7 p. Sittinger, Richard, Sittinger, Cheryl, and Voynick, Steve, 1998, The Sweet Home Mine, 18731989: The Mineralogical Record, v. 29, n. 4, p. 11-20. Wenrich, K. J., 1998, Sweet Home Rhodochrosite: What Makes it So Cherry Red? Mineralogical Record, 29:123-32. Wilson, Wendell, 2014, Des Sacco: A Few African Favorites: The Mineralogical Record: p. 102.

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Rhodochrosite Wall: At the Denver Museum of Natural History, Rocks and Minerals, 72(4): 240-243. Murphy, Jack A., 2011, On the Sunnyside in The San Juan Triangle of Colorado - Mountains of Minerals: Lithographie, LLC., Denver, Colorado, Mineral monograph no. 15: p. 68-77. Murphy, Jack A. and Peter J. Modreski, 2002, A Tour of Colorado Gemstone Localities, Rocks & Minerals, 77(4): 218-238. Paty, Alma Hale, 2001 Taking Time for Timely Exhibits in Denver, Geotimes, 46(11): 63. Polgari, Marta, Lorant Biro, Elmer Pal-Molnar, Gabor Dobosi, Bernadett Bajnoczi, Tibor Nemeth, Viktoria Kovaks Kis and Tamas Vigh, 2013, Rhodochrosite-Bearing Concretions from a Jurassic Manganese Ore Mineralization – Urkut, Hungary, Carpathian Journal of Earth and Vol. 68, No. 4 | www.rmag.org

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2019 RMAG FOUNDATION SCHOLARSHIP WINNERS RACHEL HAVRANEK

During 2019, the RMAG Foundation honors eight research scholarship awardees, listed here with their universities or college and their research topics. Our congratulations to the winners.

University of Colorado, Boulder, Dudley and Marion Bolyard/University of Colorado Scholarship Developing a multiport soil vapor storage system

ELIJAH ADENIYI

ROBIN HILDERMAN

Montana State University, Norman F. Foster Memorial Scholarship The origin and timing of CO2 reservoired in the Duperow Formation, Kevin Dome, Montana

Colorado College, Philip J. McKenna Memorial Scholarship La-ICP-MS of U-Pb zircon and Hf isotope geochemistry of the Hinsdale Formation San Juan, Colorado

KATELYN BARTON

ELISABETH G. RAU

Brigham Young University, Michael S. Johnson Scholarship Links between eruptive styles and magmatic evolution at shield volcanoes: Snake River Plain, Idaho

Baylor University, Robert M. Cluff Memorial Scholarship Prediction of depositional facies and associated rock quality attributes from wireline logs within the Late Devonian Duvernay Formation

MICHAEL FROTHINGHAM University of Colorado, Boulder, Stone/Hollberg Memorial Scholarship Crystal- to Crustal-Scale Seismic Anisotropy of Continental Crust

TREVOR VAN DYKE Iowa State University, Veterans Memorial Scholarship The geology, geochemistry, and mineralogy of the metamorphosed Dawson massive sulfide and gold deposit, Canyon City, Colorado

ZOE HAVELENA New Mexico Institute of Mining and Technology, Gary Babcock Memorial Scholarship Sulfuric acid speleogenesis of caves in the Eastern Great Basin

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CARTOON

By Debra Higley

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WELCOME NEW RMAG MEMBERS!

Zeynep Baran

Andrew Gordon

Matthew Sebade

is an Assistant Professor at SDSMT in Rapid City, South Dakota.

is a Geologist at Ultra Petroleum and lives in Englewood, Colorado.

is a Geologist at Chesapeake Energy and lives in Edmond, Oklahoma.

is a Geologist at Zavanna LLC and lives in Denver, Colorado.

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works at Drillinginfo and lives in Denver, Colorado.

lives in Boulder, Colorado.

works at Hawkwood Energy and lives in Denver, Colorado.

is a Geologist/Petrophysicist at Council Oak Resources and lives in Mannford, Oklahoma.

Amber Barnett Dylan Brazier Eric Dew

is a Sr. District Geologist at Samson Resources II and lives in Tulsa, Oklahoma.

Richard Gaber

is a Sr. Geoscientist and lives in Littleton, Colorado.

Katie Logan

Rodney Rice John Sadler

is in Onshore Project Development at TGS and lives in Houston, Texas.

Heidi Schoenstein

lives in Grand Junction, Colorado.

Tim Shane

Mark Sutcliffe

James Van Hook

is a student at Colorado State University and lives in Fort Collins, Colorado.

Alan Vennemann works at Drillinginfo and lives in Denver, Colorado.

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IN THE PIPELINE APRIL 3, 2019

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RMAG Luncheon. Speaker Lisa Morgan. “The Hydrothermal System beneath Yellowstone Lake (and why it’s so important to map lakes in Yellowstone).” Maggiano’s Downtown Denver.

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APRIL 12, 2019 DIPS Luncheon. Members $20 and Nonmembers $25. For more information or to RSVP via email to kurt.reisser@gmail.com.

APRIL 25-28, 2019 RMAG Book Cliffs Field Trip. Trip Leaders: William and David Little. Contact: staff@rmag.org MAY 1, 2019

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