13.04.2014 Views

geothermal resource potential of the safford-san simon basin, arizona

geothermal resource potential of the safford-san simon basin, arizona

geothermal resource potential of the safford-san simon basin, arizona

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

similar to <strong>the</strong> Precambrian granite in outcrops at Clifton, a likely source area<br />

for <strong>the</strong> red granite clasts in <strong>basin</strong>-fill gravels.<br />

An alternate interpretation<br />

explains <strong>the</strong> "red granite" ei<strong>the</strong>r as a highly indurated conglomerate<br />

with granite clasts or as a granite boulder.<br />

These alternate explanations<br />

seem more speculative, however, when considering that well D-7-2-2CDB lies<br />

astride a Bouguer gravity high which encompasses <strong>the</strong> areal extent <strong>of</strong> copper<br />

mineralization associated with "Laramide" volcanic rock and stocks (Figure 14 ) .<br />

In <strong>the</strong> Safford Basin, six miles west <strong>of</strong> Buena Vista, well D-7-26-26ABA,<br />

bottoms in 670 m <strong>of</strong> siltstone and mudstone, which are herein correlated with<br />

<strong>the</strong> green clay facies <strong>of</strong> Harbour (1966) (files, USGS, Tucson). Steep Bouguer<br />

gravity gradients between this well and Buena Vista, coupled with <strong>the</strong> much<br />

greater thickness <strong>of</strong> <strong>basin</strong> fill in well D-7-26-26AB~suggesta large normal<br />

fault zone(s) trending west-northwest (Figures 12 and 13).<br />

East <strong>of</strong> Buena Vista, ano<strong>the</strong>r fault zone is inferred from surface geology<br />

and <strong>the</strong> lithology log <strong>of</strong> well D-6-28-3lAAB.<br />

This well is in sediment to 165 m<br />

at total depth (files, USGS, Tucson). Less than a quarter <strong>of</strong> a mile east <strong>of</strong><br />

well D-6-28-3lAAB, Tertiary basaltic andesite is observed at <strong>the</strong> surface.<br />

A<br />

normal fault striking north-nor<strong>the</strong>ast whose hanging wall is west would explain<br />

<strong>the</strong> lithologic incongruity between <strong>the</strong> well and nearby surface exposures.<br />

This inferred fault may intersect <strong>the</strong> Butte fault zone 1.5 miles southwest<br />

<strong>of</strong> well D-6-28-3lAAB. A photo lineament extends south-southwest from, and<br />

on strike with, <strong>the</strong> inferred fault.<br />

Just north <strong>of</strong> San Jose Wash, a scarp<br />

facing northwest and coinciding with <strong>the</strong> lineament is easily seen in black<br />

and white U-2 photographs.<br />

Origin <strong>of</strong> <strong>the</strong> scarp is speculative; however, terracing<br />

is <strong>the</strong> stronger explanation because <strong>the</strong> present-day Gila River flood<br />

plain parallels <strong>the</strong> scarp strike.<br />

Detailed surface mapping <strong>of</strong> this area<br />

seems warranted in order to determine if <strong>the</strong> scarp has a tectonic or ero-<br />

45

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!