Ask a Geologist Common Q&A

Hi Cyndi,

Thanks for your interesting question about water usage in gold mining. As a bit of background, managing water is one of the most important environmental considerations at mining operations. The most common uses of water in mining are in processing ore (e.g., grinding, flotation) and in watering mining roads to suppress dust (Stevens, 2010). The sources of water for mining in Arizona vary depending on the local geography, but include aquifers, Central Arizona Project (CAP), surficial waters, captured precipitation, and even water from the mine itself if the mine is being actively dewatered (Singh, 2010).

Estimates for average water consumption at a mine site vary considerably based on the processing method applied (e.g., heap leaching, flotation, gravity), but a global summary for water withdrawals for gold mines found the ‘average’ gold mine used ~0.350 m3/metric ton of ore-grade rock (Gunson, 2013). As such, the annual amount of water used will depend on how much mineralized material is being mined each year. While this doesn’t give a nice average use, it is more robust as it considers the size of the operation. The current water usage due to gold mining in the Upper Hassayampa and Agua Fria basins should be fairly low to our knowledge as there are no significant gold operations active in the area, with the historic gold mines in the area being defunct. What little gold production is happening is due to a few relatively small placer operations and rare, very minor pilot operations to test some of the historic mines. A larger source of water in the area is likely from industrial minerals (e.g., sand and gravel) mining operations.

Cheers,
Carson Richardson (AZGS Economic Geologist)

References:
Gunson, A. J., 2013, Quantifying, reducing, and improving mine water use: Unpublished Ph.D. dissertation, University of British Columbia, Vancouver, 258 p. URL: https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0071942

Singh, M. M., 2010, Water consumption at copper mines in Arizona, Arizona Department of Mines and Mineral Resources, Special Report 29, 16 p. URL: http://repository.azgs.az.gov/uri_gin/azgs/dlio/1295

Stevens, R., 2010, Mineral exploration and mining essentials: Port Coquitlam, British Columbia, Pakawau GeoManagement, Inc., 322 p.

Chris,

I’m attaching a snippet from the USGS Mayer geologic quadrangle published in 1972. The Long Draw area is surrounded by sediment largely drawn from the Hickey Formation – mostly Miocene age basalts. There are banded iron deposits in AZ.

Below this map is a coarse map showing the iron deposits from AZGS Bull 180. You can retrieve the map and additional info from our Bulletin 180 - http://repository.azgs.az.gov/uri_gin/azgs/dlio/1005   See Part 3, p. 10 – 17 (p168 to 182 in the document.)

Good luck with it. Mike

U.S. Geological Survey Geologic Quadrangle Map GQ-996 U.S. Geological Survey Geologic Quadrangle Map GQ-996

Hi Thomas,

Well it is certainly conical, but conical shape does not a cinder cone make. I copied the description for that area from our 1:1,000,000 scale map and pasted it below.

I don't believe this hill is or was a cinder cone. The rock debris certainly looks like basaltic rubble, but more likely to be associated with lava flows.  Mike

Middle Miocene to Oligocene Volcanic Rocks (11-38 Ma)

Lava, tuff, fine-grained intrusive rock, and diverse pyroclastic rocks. These compositionally variable volcanic rocks include basalt, andesite, dacite, and rhyolite. Thick felsic volcanic sequences form prominent cliffs and range fronts in the Black (Mohave County), Superstition, Kofa, Eagletail, Galiuro, and Chiricahua Mountains. This unit includes regionally extensive ash-flow tuffs, such as the Peach Springs tuff of northwestern Arizona and the Apache Leap tuff east of Phoenix. Most volcanic rocks are 20-30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona, but this unit includes some late Eocene rocks near the New Mexico border in east-central Arizona.

Hi Nicole,

Steve Reynolds (Arizona State University) has a marvelous geologic map and accompanying description for the South Mountains.

Reynolds, S.J., 1985, Geology of the South Mountains, Central Arizona. Arizona Geological Survey Bulletin-195, 75 p., 1 map plate, scale 1:24,000.

And if you are interested, Julia Johnson field trip guide to the Phoenix Mountains is excellent, too.

Johnson, J.A., Reynolds, S.J., and Jones, D.A., 2003, Geologic map of the Phoenix Mountains, Central Arizona: Arizona Geological Survey Contributed Map CM-04-A, map scale 1:24,000, 16 p.

Enjoy the geology.

Mike

There are two possible solutions (forgive the pun). Case hardening - where an amorphous silica gel precipitates locally resulting in areas of greater or lesser competency. In other words, the rock mantled by the silica gel is harder and more difficult to erode.  Alternatively, fractures (joints) in the sandstone will provide a conduit for naturally acidic waters to percolate through the rock. When those waters encounter lower permeability layers, the water seeps out of the rock causing local, lateral erosion resulting in alcoves as shown below. For illustrations and more detailed descriptions, download John Bezy’s 44-page “A guide to the Geology of the Sedona & Oak Creek Canyon area, Arizona’.  (Free to download) Case hardening and alcove formation are explained on page 29 and 30 respectively. Great question, thanks! Mike

Hello Connor,

That data should be available through the National Geothermal Data System (NGDS) that AZGS and our partners AASG, USGS, SMU, among others,  build in 2010-2014 http://geothermaldata.org/.  There are about 10 million data objects in the NGDS including geothermal-related data from all 50 states.

Let me know if you are having trouble compiling those data. There are still one or two individuals around who designed the data structure and they may have ideas for teasing out that data.

Mike

Hi Tony,

BLM should have the info; they replaced the LR2000 site, but it is not as robust. You need to call or e-mail BLM office in Phoenix:  602.417.9200 or blm_az_asoweb@blm.gov They should have the data you are looking for.

Good luck with it.
Mike

Hi Sherry,

Examining Google Earth imagery, it appears that Laveen Village is built on former agricultural fields northwest of South Mountain. Frequently, agriculture fields are poorly compacted during residential construction. As a result local sag features are not terribly uncommon.

For another viewpoint, you might reach out to NCRS - Natural Resource Conservation Service - in the PHX area. Soils are what they do and they may have further insight to share.

For inquiries:  AZinfo@nrcs.usda.gov   Phone: (602) 280-8808

Hi Olow:

There are several different ways to show groundwater contours. Have a look at the URLs below for a range of treatments.  Good luck with it. Mike

Depth to Groundwater map - Tucson AZ    https://www.tucsonaz.gov/water/groundwater-maps 

Groundwater elevation map - Tucson AZ    same URL

Topo-Groundwater Contour Map  - http://www.gly.uga.edu/railsback/1121GWMap3.jpeg  

               This site is designed for students and some excellent graphics:  http://www.gly.uga.edu/railsback/GeologicalDiagrams2.html See the groundwater section.

Hi Kaitline,
Good question. Earth fissures tend to be curvilinear and frequently cut across drainages and erosional features. Also, a gully floor typically is graded downslope; fissures frequently are not so well graded and include local depressions where water pools. Have a look at some of our fissure pictures at our AZGS photo gallery (http://azgs.arizona.edu/azgs-photo-tags/earth-fissure)

I can't tell from your image, but it does look like a local erosional feature, which tend to follow local drainages. Let me know if I can help further.

All mapped earth fissures in Arizona are displayed at the Natural Hazards in Arizona Viewer. Check it out at: http://uagis.maps.arcgis.com/apps/webappviewer/index.html?id=98729f76e46...

Mike