{"id":130,"date":"2018-03-24T12:00:20","date_gmt":"2018-03-24T19:00:20","guid":{"rendered":"http:\/\/mollymarieprospect.com\/blog\/?page_id=130"},"modified":"2022-01-31T19:45:32","modified_gmt":"2022-02-01T02:45:32","slug":"stratigraphy","status":"publish","type":"page","link":"https:\/\/mollymarieprospect.com\/blog\/geology\/stratigraphy","title":{"rendered":"Stratigraphy"},"content":{"rendered":"
It is assumed that the pre-ore stratigraphy is the same as that of Goldfield 2-1\/2 miles away that John Wilburn describes in his pamphlet “Goldfield Mining District Geology and Ore Deposits”.\u00a0 Below is a simplified diagram per Wilburn’s descriptions:<\/div>\n
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Molly Marie Simplified Stratigraphy<\/figcaption><\/figure>\n<\/div>\n<\/div>\n
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Tuff <\/span><\/span><\/strong>– <\/span>Occurs as a thin bed generally less than 50 feet thick, deposited over basalt and gossan breccias on the ridges on the east side of the Molly Marie Prospect.\u00a0 This tuff is believed to have originated from a diatreme near the the center of the claim group.\u00a0 This tuff was deposited pre-ore and is often found saturated with apatite,\u00a0 sygenic with ore formation.
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\n<\/span>Basalt<\/strong> <\/span><\/span>– There are two layers of basalt and their thickness in total is about 130 feet thick at Goldfield.\u00a0 As described by Wilburn, there is a +\/-1 meter bed\u00a0 of welded tuff between the layers of basalt, the Saddle Rock Tuff.
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The lower portion of the basalt is named the Weekes Wash basalt(Fodor, S.K. Vetter) and is higher in silica than the upper basalt, The upper is the Cottonwood Spring basalt, and some trends to andesite. <\/span><\/span><\/div>\n
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On the Molly Marie Prospect, the basalt varies in thickness because of erosion and silicification.\u00a0 The basalt varies in thickness from 0 to an estimated 80 feet thick.\u00a0 The contact between the basalt can be seen in several places.\u00a0\u00a0 Silicification of the basalt has created “hills”\u00a0 because the silicified areas are resistant to erosion.
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Whitetail Assemblage <\/span><\/span><\/strong>– <\/span>Wilburn describes the Whitetail as lying unconformably on the granite up to a thickness of 500 feet.\u00a0 The upper Whitetail is approximately 250 feet thick, and contains more conglomerate than the lower Whitetail, varying from thin conglomerate beds in the sandstone to dense cobbles at the top.\u00a0 A large percentage of the cobbles are limestone and marble. The Whitetail on west side of the Prospect has been brecciated,\u00a0 and forms the large ridges of phreatic breccia on the caldera margin.
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The lower portion of the Whitetail (approximately 250 feet thick) is nearly conglomerate-free. Snotnicki & Ferguson (Geologic Map of the Goldfield Quadrangle) label the lower portion of the Whitetail as Tertiary Sandstone(Ts). This arkosic sandstone is composed of fragments of eroded granite.<\/p>\n

Pre – Cambrian Granite <\/span><\/span><\/strong>– <\/span>This is the basement rock and is called the Ruin granite.\u00a0 It varies in texture from a medium equi-granular granite to that of pegmatite granite with large phenocrysts of feldspar approximately 2 inches in width.\u00a0 The granite is highly magnetic in a zone approximately 400 to 500 yards wide surrounding the caldera.
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Some of the Ruin granite surrounding the Molly Marie and other calderas in the area has been altered to a Syenite with an amphibole matrix.\u00a0 It closely resembles that original Syenite found in Syene, Eqypt which also has large phenocrysts.\u00a0 One dike of this Syenite is found within the Molly Marie caldera.<\/p>\n

The arkosic breccias on the west side of the Molly Marie Caldera post-date the granite, Whitetail assemblage, and basalt.\u00a0 Rhyolite dikes (and the volcanic neck) postdate the granite, Whitetail assemblage, and basalt.<\/p>\n<\/div>\n

Below is a geologic map of the claim group.\u00a0 This is a portion of the Skotnicki<\/em>, S.J. and Ferguson, C.A., 1995, Geologic map<\/em> of the Goldfield Quadrangle and the northern part of the Superstition<\/em> Mountains. SW Quadrangle, Maricopa and Pinal Counties, Arizona. Arizona Geological Survey Open File Report, OFR-95-09, 2 map sheets, map scale 1:24,000, .\u00a0 As shown on the pages within, the large volcanic neck of Rhyolite porphyry\u00a0 was not identified or mapped on the east side of the claim group.
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The area inside the claim group has dropped over 700 feet respective to the granite on the outside of the claim group. <\/span><\/p>\n

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\"http:\/\/mollymarieprospect.com\/Diagrams\/Realgeo.jpg\"<\/p>\n

Rhyolite and Rhyolite Porphyry<\/strong><\/p>\n

Short dikes of high-silica Rhyolite and Rhyolite Porphyry cut all formations described above.<\/p>\n

Below is a link to the detailed geologic maps, cross-sections, and reports of the Goldfield quadrangle and surrounding area:<\/p>\n<\/div>\n

http:\/\/repository.azgs.az.gov\/uri_gin\/azgs\/dlio\/246<\/a><\/p>\n<\/div>\n

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