The Jarbidge Mining District in northern Elko County, Nevada (Figure 1) hosts
\nlow-sulfidation epithermal quartz-adularia veins in mid-Miocene rhyolitic volcanic
\nrocks. Greater than 355,000 ounces of gold and 1,600,000 of silver were produced from
\napproximately 800,000 tons of ore between 1918 and 1932 (LaPointe et. al., 1991). The
\nsilver to gold ratio of the ore was approximately 10:1. The district was the largest
\nproducer of gold in Nevada for a brief period prior to the success of the Nevada Consolidated
\nCopper Co. operations at Ely, Nevada (Schrader, 1923). All production was
\nfrom underground workings, typically utilizing the shrinkage-stoping method which
\nrenders modern access into the mines very dangerous. Complex faulting and vein
\ndevelopment in conjunction with multiple laterally discontinuous but very similar
\nrhyolite eruptive units have hindered historic and modern exploration efforts.
\nExposures of productive veins in the district are extremely rare and descriptions
\nof veins are primarily based on examinations conducted during the main period
\nof mining, primarily by Frank Schrader in 1920 (Schrader, 1923). Primary ore minerals
\nare native gold, electrum, argentite (Ag2S), and naumannite (Ag2Se) (Figure 2).
\nThey occur in a variety of styles including comminuted margins of veins, hydrothermal
\nbreccia lenses associated with veins and within finely crystalline quartz veins and
\nveinlets that typically contain late adularia along the margins (Figure 3). Multiple
\nvein deposition events and contemporaneous minor faulting with gouge development
\nare common. Where visible, electrum is typically associated with or adjacent to small
\n(< 2 mm) blebs of argentite or naumannite. Plate-texture of quartz and adularia after
\ncalcite, named \u201cfish-scale quartz\u201d by early miners, is common in the district and
\nis compelling evidence for multiple boiling events. Within a specific vein formation
\nevent adularia is typically deposited later than quartz, however, this later-deposited
\nadularia is often encapsulated by quartz deposited during a subsequent depositional
\npulse. Adularia dominant veins typically have low gold content. Throughout the Jarbidge
\nDistrict gold in the veins typically occurs as small particles which although
\ncommonly free-milling is not suitable for recovery by gravity methods or amalgamation.
\nThis, in conjunction with high stream gradients and very few exposed bedrock
\ntraps, is the reason there was very little placer gold recovered in the district and that
\nsignificant lode mineralization was discovered very late relative to other epithermal
\nvein districts in Nevada.
\nKey Words: epithermal, adularia, Miocene, rhyolite, gold<\/p>\n","protected":false},"featured_media":5166,"comment_status":"closed","ping_status":"closed","template":"","meta":{"pmpro_default_level":""},"product_cat":[857,154],"product_tag":[],"_links":{"self":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product\/5164"}],"collection":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/types\/product"}],"replies":[{"embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/comments?post=5164"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/media\/5166"}],"wp:attachment":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/media?parent=5164"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product_cat?post=5164"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product_tag?post=5164"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}