Geology

Out of the wildfire and into the flood – Arizona Summer 2017

After several quiet years, Arizona has had a very active wildfire season. Halfway through 2017, just over 352,000 acres have been burned in Arizona by wildfires of >100 acres in size (Inciweb for Arizona: https://inciweb.nwcg.gov/state/3/). This was the worst fire season since the record burns of 2011, and is almost 4 times as many acres burned than in 2013 (Table 1; Southwest Coordination Center: https://gacc.nifc.gov/swcc, accessed July 12, 2017). While the worst part of the fire season is likely behind us, based on recent years we can expect to see more wildfires in the fall. Most of the 2017 burned acreage has been on land managed by the U.S. Forest Service (USFS), followed by Arizona State lands (AZFD), Bureau of Indian Affairs (BIA), and Bureau of Land Management (BLM).

As the monsoon season ramps up, it is time to be cognizant of potential post-fire flooding and debris flows. Both floods and debris flows pose significant hazards to human health, property and infrastructure, and both carry a significant amount of sediment, woody material and rocks. Debris flows can be more dangerous, however, as they resemble slurries of dense, fast-moving concrete that carry more sediment and woody debris and larger caliber rocks (maybe up to basketball sized rocks in floods and car or truck sized boulders in debris flows).

Wildfires significantly impact watershed hydrology, causing much more runoff to occur and frequently triggering post-fire floods and debris flows. In the absence of wildfire, unburned vegetation intercepts raindrops, mitigating the impacts of high-velocity drops on soils. Depending on the burn severity of the wildfire, interception of rainfall by plants can be severely reduced or completely eliminated. At the same time, infiltration of water into the soil is impeded by the presence of ash and fire-related changes to soils (e.g. hyper-dry soils, hydrophobicity, and the destruction of organic matter). These changes result in increased runoff volumes and velocities such that smaller, short-lived monsoon storms can generate tremendous runoff, flooding, and debris flows, and do a huge amount of geomorphic work (i.e. erosion and transportation of sediment) in a very short period of time.

Post by Ann Youberg

Read more at: http://arizonageology.blogspot.com/2017/07/out-of-wildfire-and-into-flood-arizona.html

Mineral Resources of some Arizona National Monuments

In view of President Trump’s program to reassess some National Monuments, the Arizona Geological Survey has released flyers regarding the mineral potential of four Arizona monuments: Ironwood Forest, Grand Canyon-Parashant, Sonoran Desert, and Vermilion Cliffs. You may read these short flyers here: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1715

Ironwood Forest, about 35 miles northwest of Tucson, has an active copper mine and, according to local geologists, much more potential resources both east and west of the active mine. You can read about the history of the Silver Bell mine in a new paper by geologist David Briggs here: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1714 Briggs notes: “Over the past 130 years, the Silver Bell mining district yielded approximately 2.27 billion pounds of copper, 6.6 million pounds of molybdenum, 3.7 million pounds of lead, 40.8 million pounds of zinc, 2,100 ounces of gold and 5.95 million ounces of silver.”

The Grand Canyon-Parashant area has produced copper, uranium, lead, zinc, gold, and Silver from breccia pipe deposits within what is now the monument. Breccia pipes are vertical pipe-like structures comprising broken rock (breccia). They are collapse features that originate in the cavernous Redwall Limestone and subsequently propagate upward through upper Paleozoic and lower Mesozoic rock formation. A recent review by the Arizona Geological Survey indicates that there could be thousands of yet unexplored breccia pipes within the monument. (See my article: Breccia pipes of northwestern Arizona and their economic significance)

The Sonoran Desert monument west of Phoenix has historically produced , gold, silver, copper, and manganese from small mines. The Aguila manganese mineral district in the Big Horn Mountains produced 42 million pounds of manganese.

The Vermilion Cliffs area in northwestern Arizona has had some small production of uranium, but the AZGS concludes “ there is little geologic evidence for economic minerals deposits in the monument.”

Two of the monuments, Ironwood Forest and Grand Canyon-Parashant, have had significant mineral production and more inferred resources. Local geologists suspect there are more copper resources east and west of the active mining area of the Silver Bell mine, but that ground is effectively off-limits because it lies within Ironwood Forest National Monument. The monument was imposed over valid pre-existing mining claims. This should be taken into account in assessing their status. The imposition of National Monument designation greatly inhibits or even prevents development of valuable mineral resources.

History of the Silver Bell Mining District

The Arizona Geological Survey has just released another paper about Arizona mining: The History of the Silver Bell Mining District (AZGS Contributed Report CR-17-A). The paper is authored by geologist and mining historian David Briggs who has written about many of Arizona’s mining districts. The paper is available for free download (link).

The Silver Bell mine and the town of Silverbell are located about 36 miles northwest of Tucson, Arizona. It has produced copper and other metals since 1873 and silver since 1865. Prior to that, the Tohono O’odham Indians and/or their predecessors mined turquoise, hematite and clay, which were used for pottery, paint and decorative purposes.

The Silver Bell mine has had a colorful and sometimes contentious history. Briggs writes that “Over the past 150 years, the Silver Bell mining district evolved from a collection of small, intermittent, poorly financed and managed underground mining operations that struggled to make a profit from high-grade ores; to a small but profitable producer, deploying innovative mining practices and advancements in technology to successfully develop the district’s large, low-grade copper resource.”

Besides a detailed history of owners and operations, the report contains many historic photographs of the mining operations and the town.

Briggs: “Over past 130 years, the Silver Bell mining district yielded approximately 2.27 billion pounds of copper, 6.6 million pounds of molybdenum, 3.7 million pounds of lead, 40.8 million pounds of zinc, 2,100 ounces of gold, and 5.95 million ounces of silver.”

The mine now produces copper by leaching and electro-winning. Remaining reserves are reported to be 214.4 million tons, averaging 0.283% copper. Local geologists suspect there are more copper resources east and west of the active mining area, but that ground is effectively off-limits because it lies within Ironwood Forest National Monument. The monument was imposed over valid pre-existing mining claims. IFNM is one being reconsidered by the Trump administration.

Other papers by David Briggs:

History of the Ajo Mining District, Pima County, Arizona

History of the Warren (Bisbee) Mining District

History of the San Manuel-Kalamazoo Mine, Pinal County, Arizona

Recovery of Copper by Solution Mining Techniques

Superior, Arizona – An Old Mining Camp with Many Lives

History of the Copper Mountain (Morenci) Mining District

History of Helvetia-Rosemont Mining District, Pima County, Arizona

History of the Ajo Mining District, Pima County, Arizona by David Briggs

Geologist David Briggs has written another interesting paper on the history of mining in Arizona. This 18-page paper, History of the Ajo Mining District, Pima County, Arizona, was just published by the Arizona Geological Survey and is available as a free download: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1710

I was particularly interesting in the Ajo paper because as a geologist, I conducted exploration at the mine and in the district. Although the mine is now inactive, there is remaining mineralization that can be mined given the right economic conditions. The Ajo orebody is particularly interesting to geologists because paleomagnetic and geologic evidence indicates that the Ajo ore deposit has been tilted to the south a total of approximately 120 degrees in two separate tectonic events. (Source) There is also speculation that a detached piece of the original orebody lies hidden nearby.

Briggs begins his story as follows: “The hostile environment of southwestern Arizona’s low desert presented many challenges to those who sought to discover and exploit the mineral wealth

of the region. Ajo’s remote location combined with hot summer days and scarce water created a number of obstacles that needed to be overcome. Despite these impediments, the district’s wealth was mined by Native Americans long before the arrival of first Spanish explorers, who recognized its potential soon after establishing outposts in this region.”

The Ajo area has a long history. Prior to the arrival of the first Spanish explorers in the 1530’s, the native Tohono O’odham Indians and their ancestors mined hematite, an iron oxide, which they used as body paint. Establishment of Spanish missions in Southern Arizona provided bases from which prospectors combed the country.

With the signing of the Treaty of Guadalupe Hidalgo at the end of the Mexican American War on February 2, 1848, and the subsequent Gadsden Purchase in June 1854, many prospectors tried their luck at Ajo.

Briggs provides great detail as he recounts the many lives of mining ventures in Ajo. Following is a very brief sketch of major events.

The first formal mining began in 1855 and a wagon road was constructed to the railroad at Gila Bend. Ore was also sent by wagon to San Diego and shipped to Swansea, Wales for smelting. High transportation costs eventually made the venture uneconomic.

Briggs recounts the era between 1898 and 1908 when the Ajo deposit saw many promotions and fraudulent mining schemes.

In 1911, the Calumet and Arizona Mining Company, which was operating mines in Bisbee, became interested in the Ajo properties and acquired the New Cornelia Copper Company which owned Ajo at the time. Calumet began an extensive drilling program which confirmed the presence of a large sulfide body of mineralization. They began open pit mining in 1915.

In 1931, Phelps Dodge merged with Calumet and Arizona Mining Company and continued to operate the mine which they did until 1985 when a combination of low copper prices and stricter regulations for smelter air quality caused the company to close the mine.

The Ajo property is now owned by Freeport-McMoRan, Inc. through its merger with Phelps Dodge. According to Briggs, “Freeport continues to periodically assess the economic feasibility of returning the Ajo project to production. As of December 31, 2015, this project is estimated to contain a sulfide resource of 482 million short tons, averaging 0.40% copper, 0.010% molybdenum, 0.002 oz. of gold/ton and 0.023 oz. of silver/ton.”

Other papers by David Briggs, published by the Arizona Geological Survey:

History of the Warren (Bisbee) Mining District

History of the San Manuel-Kalamazoo Mine, Pinal County, Arizona

Recovery of Copper by Solution Mining Techniques

Superior, Arizona – An Old Mining Camp with Many Lives

History of the Copper Mountain (Morenci) Mining District

History of Helvetia-Rosemont Mining District, Pima County, Arizona

 

The Pirate Fault of Canada del Oro

pirate-fault

The Pirate fault forms the western boundary of the Santa Catalina Mountains near Tucson and separates the mountains from the Cañada del Oro basin to the west. The fault occurs just east of the communities of Saddlebrooke, Catalina, and Oro Valley. Remnants of this fault, exposed for about 15 miles along the mountain front, are described in a paper from the Arizona Geological Survey (see reference below). The paper describes geological features of 10 sites along the fault trace.

 

The AZGS says that this fault represents an expression of Basin & Range faulting which was active between 12 million and 6 million years ago. Vertical displacement on the fault is estimated to be about 2.5 miles with the west side down relative to the Santa Catalina Mountains uplift on the east. The fault dips from 50° to 55° west along its entire trace. The Basin & Range era was a time of crustal extension which formed much of the topography in Southern Arizona.

According to AZGS: “ Following cessation of active uplift, the fault was buried under detritus eroded from the uplifted Santa Catalina block and, currently, is being exhumed by the down-cutting Cañada del Oro and its tributaries. This field examination reveals the fault to have left a sparse but diverse collection of remains implying a varied history of fault development and evolution.”

“Deposition of basin-fill material in the Cañada del Oro basin culminated in Pleistocene time (1-2 Ma) following cessation of active uplift on the Pirate fault. Alluvium deposited during this latter time forms the high-stand surface of coalescent alluvial fans composed mostly of detritus eroded from the Santa Catalina Mountains.” That material contains placer gold deposits. The gold was derived from gold-bearing quartz veins in the Santa Catalina Mountains.

The Pirate fault disappears beneath alluvium to both the south and north. If one projects the northern trace, the Pirate fault could intersect the southeast-to-northwest trending Mogul fault. Indeed, near the projected intersection is a decorative stone quarry whose source rock is highly fractured, deformed, and altered bedrock that may be evidence of the projected fault intersection.

Parts of the exposed Pirate fault are stained red by hematite, an iron oxide, suggesting that mineralizing hydrothermal solutions were present during the development of the fault. The exact nature of this mineralization is enigmatic and according to the AZGS, “would seem to defy ready explanation.” “The picture that emerges is that of the Pirate fault as a geologic entity whose tenure as an active participant in the extensional Basin-Range tectonic event has left behind a somewhat sparse and locally enigmatic set of remains from which to infer, caveat emptor, its past.”
Reference:

Hoxie, D.T., Exhuming the Remains of the Inactive Mountain-Front Pirate Fault, Santa Catalina Mountains, Southeastern Arizona. Arizona Geological Survey, Contributed Report CR-12-F, 18p.

Free download: http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1483/cr-12-f_pirate_fault_report_v.1.pdf

See also: The Gold of Cañada del Oro

The Basin & Range Province of North America

American Geosciences Institute’s Critical Issues program

agi

The Arizona Geological Survey’s winter e-magazine features an article about the American Geosciences Institute’s Critical Issues program (www.americangeosciences.org/critical-issues).

The aim of this AGI program is to pioneer a new approach to sharing societally-relevant science with state and local decision makers. “Here in Arizona, we are sharing this with state and local decision-makers to help them wrap their heads around the complex issues involving groundwater, geologic hazards, and sustainable natural resource management.”

The program aims to support connections and communication between the geoscience community and decision makers. Although the program caters to decision makers at all levels, it particularly focuses on state and local decision makers because these stakeholders are commonly underserved by geoscience policy efforts.

The program convenes meetings, such as the AGI Critical Issues Forum, but its main interface is a web-based platform of resources that bring the expertise of the geoscience community to decision makers by offering a curated selection of information products from sources that include state geological surveys, federal and state agencies, and AGI’s member societies.

The Critical Issues program offers the following freely accessible information services:

Research database: Over 4,000 publications primarily from state geological surveys and the U.S. Geological Survey.

Webinars: Free webinars on a variety of topics that bring geoscientists and decision makers together to discuss potential solutions to challenges at the interface of geoscience and society.

Maps & Visualizations: 144 interactive maps and visualizations covering all 50 states and the District of Columbia.

Case studies: A new product that is coming online in Spring 2017. Specific applications of geoscience to societal problems.

Fact Sheets: A new product that is coming online in Spring 2017. Provide more in-depth information on the big issues.

Frequently Asked Questions: 105 questions on topics including: climate, energy, hazards, mineral resources, and water.

Read more at:

http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1709/agi_critical_issues4-final.pdf

This AZGS e-Magazine also includes an article about groundwater use in the United States.

 

American mineral production for 2016

The U.S. Geological Survey has just released their annual summary of non-fuel mineral production in the U.S. for 2016. They estimate that the value of all non-fuel minerals produced from U.S. mines was $74.6 billion, a slight increase over production in 2015. “ Domestic raw materials and domestically recycled materials were used to process mineral materials worth $675 billion. These mineral materials were, in turn, consumed by downstream industries with an estimated value of $2.78 trillion in 2016.”

Principal contributors to the total value of metal mine production in 2016 were gold (37%), copper (29%), iron ore (15%), and zinc (7%). The estimated value of U.S. industrial minerals production in 2016 was $51.6 billion which was dominated by crushed stone (31%), cement (18%), and construction sand and gravel (17%).

Nevada was ranked first with a total mineral production value of $7.65 billion, mainly from gold. Arizona came in second in total production with a value of $5.56 billion and first in U.S. copper production. Texas, California, Minnesota, Florida, Alaska, Michigan, Wyoming, Missouri, and Utah, in that order, were next in value of production.

“In 2016, U.S. production of 13 mineral commodities was valued at more than $1 billion each. These were, in decreasing order of value, crushed stone, cement, construction sand and gravel, gold, copper, industrial sand and gravel, iron ore (shipped), lime, phosphate rock, salt, soda ash, zinc, and clays (all types).” Does that order surprise you?

Most of the material mined (stone, sand, lime, clay) is used in construction of our infrastructure.

Gold is used as coinage and to manufacture jewelry. Because gold does not corrode, it is used in solid state electronic devices that use very low voltages and currents which are easily interrupted by corrosion or tarnish at the contact points.

Copper is used mainly to generate and transmit electricity and it occurs in all our electronic devices.

Zinc is used for galvanizing to prevent corrosion and, combined with copper to make brass. Zinc is also combined with other metals to form materials that are used in automobiles, electrical components, and household fixtures. Zinc oxide is used in the manufacture of rubber and as a skin ointment.

Iron is used mainly to make steel.

Phosphate rock is used mainly as a fertilizer and also as a nutritional supplement for animals and humans.

Soda ash (sodium carbonate) is an essential raw material used in the manufacturing of glass, detergents chemicals, softening water, making baking soda, and used in many industrial products.

“U.S. mine production of copper in 2016 increased slightly, to about 1.41 million tons, and was valued at about $6.8 billion. Arizona, New Mexico, Utah, Nevada, Montana, and Michigan, in descending order of production, accounted for more than 99% of domestic mine production; copper also was recovered in Missouri. Twenty-four mines recovered copper, 17 of which accounted for about 99% of production.”

A note on reserves and resources:

Reserves data are dynamic. They may be reduced as ore is mined and (or) the feasibility of extraction diminishes, or more commonly, they may continue to increase as additional deposits (known or recently discovered) are developed, or currently exploited deposits are more thoroughly explored and (or) new technology or economic variables improve their economic feasibility. Reserves may be considered a working inventory of mining companies’ supplies of an economically extractable mineral commodity. As such, the magnitude of that inventory is necessarily limited by many considerations, including cost of drilling, taxes, price of the mineral commodity being mined, and the demand for it. Reserves will be developed to the point of business needs and geologic limitations of economic ore grade and tonnage. For example, in 1970, identified and undiscovered world copper resources were estimated to contain 1.6 billion metric tons of copper, with reserves of about 280 million tons of copper. Since then, more than 500 million tons of copper have been produced worldwide, but world copper reserves in 2016 were estimated to be 720 million tons of copper, more than double those of 1970, despite the depletion by mining of almost double the original estimated reserves.

mineral-industry-trends-2016

As can be seen in the table above, there was a decline in the production of coal, probably due to the rise in natural gas production. Metal production also decreased. According to the USGS, “Several U.S. metal mines and processing facilities were idled or closed permanently in 2016, including iron ore mines in Michigan and Minnesota; three primary aluminum smelters in Indiana, Missouri, and Washington; one secondary zinc smelter in North Carolina; a titanium sponge facility in Utah, the only such facility in the United States; and titanium mineral operations in Virginia.” In 2016, imports made up more than one-half of the U.S. apparent consumption of 50 non-fuel mineral commodities, and the United States was 100% import reliant for 20 of those.

The 200-page report gives detailed information for each commodity.

The full report is available online here: https://minerals.usgs.gov/minerals/pubs/mcs/2017/mcs2017.pdf

A Guide to the Geology of Sabino Canyon and the Catalina Highway

The Arizona Geological Survey has recently released a 56-page booklet which points out areas of geologic interest in Sabino Canyon and along the Catalina Highway to Mount Lemmon. The booklet is available for free download here.

http://repository.azgs.az.gov/uri_gin/azgs/dlio/1526

The citation is:

Bezy, J.V., 2004, A Guide to the Geology of Sabinho Canyon and the Catalina Highway. Arizona Geological Survey Down to Earth, DTE #17, 56 p.

AZGS introduces the booklet:

“ Upper Sabino Canyon Road, also known as the 1 Sabino Canyon Shuttle Route, and the Catalina Highway to Mount Lemmon offer a variety of spectacular geologic features. Because of the relatively sparse vegetation in the lower part of the range, most of these features are easy to recognize and photograph. Some of these features are common throughout this southern part of the Santa Catalina Mountains. Others occur in many other parts of the American Southwest. This booklet is your field guide to the geology of this spectacular mountain landscape. All of the geologic features described in the text can be reached by short walks from the Sabino Canyon Shuttle Route or the Catalina Highway. This book is written for the visitor who has an interest in geology, but who may not have had formal training in the subject. It may also help assure that the visiting geologist does not overlook some of the features described.”

The booklet provides short geologic descriptions of Sabino Canyon and the Catalina Mountains, and describes 11 features in Sabino Canyon and 14 features along the Catalina Highway, all of which are illustrated by photographs, maps, and diagrams. This booklet can make your visit to these areas more interesting and informative.

Below are maps of Sabino Canyon and the Catalina Highway showing the location of geologic features described.

sabino-canyon-features

catalina-highway-features

More articles on Tucson area geology:

Beneath the Tucson Valley

Gold of Cañada del Oro and rumors of treasure

Old mines of the Tucson Mountains

History of the Copper Mountain (Morenci) Mining District, Greenlee County, Arizona

morenci-1

The Arizona Geological Survey has just published a well-written history of the Morenci, Arizona, mining district. The report was written by geologist David F. Briggs and was published as AGS Contributed report Cr-16-C. The 79-page report is available for free download:
http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1695/cr-16-c_morenci_0.pdf

The Copper Mountain (Morenci) mining district is located approximately 115 miles northeast of Tucson, Arizona.

Mining began in 1873. This district has produced more than 36 billion pounds of copper from 1873 to 2015. Since 1985 is has been America’s largest domestic copper producer.

The discovery of copper at Morenci during the turbulent years of the American Civil War brought new opportunities for many, but foreshadowed the end of a way of life for Native Americans, who had lived in the region for millennia. A diverse cast of characters has played a role in Morenci’s history, including veterans who ventured west after the war, as well as immigrants eager to make a new life in America.

Briggs provides an interesting narrative of the development of the district as different companies gradually consolidated the mines. Briggs breaks the history into five phases of development as the owner(s) dealt with different types of ore, changing technology, new discoveries, and the sometimes volatile copper market.

Phelps Dodge Corporation operated the district beginning in 1917. Freeport-McMoRan Copper and Gold, Inc. (renamed Freeport-McMoRan, Inc. in July 2014) acquired an 85% interest in the Morenci project through its merger with the Phelps Dodge Corporation in March 2007, and has been operating the mine since then.

The report contains many maps and both current and historical photographs. This report is an interesting read and its story is one that was similar to that of many mines in the West.

morenci-3

morenci-2

 More reports from AZGS:

AZGS field guides to Arizona Geology

A guide to the geology of the Sedona & Oak Creek Canyon area of Arizona

A Guide to the Geology of the Santa Catalina Mountains

A Guide to the Geology of Organ Pipe Cactus National Monument and the Pinacate Biosphere Reserve

A Guide to the Geology of the Flagstaff Area

A Guide to Geology of Petrified Forest National Park

A Guide to Oak Creek-Mormon Lake Graben

AZGS Guides to Northern Arizona Geology

History of the Copper Mountain (Morenci) Mining District, Greenlee County, Arizona