{"id":2306,"date":"2019-10-02T19:49:19","date_gmt":"2019-10-02T19:49:19","guid":{"rendered":"https:\/\/www.gsnv.org\/shop\/geometry-of-the-neoproterozoic-continental-break-up-and-implications-for-location-of-nevadan-mineral-belts\/"},"modified":"2020-02-24T18:16:56","modified_gmt":"2020-02-24T18:16:56","slug":"geometry-of-the-neoproterozoic-continental-break-up-and-implications-for-location-of-nevadan-mineral-belts","status":"publish","type":"product","link":"https:\/\/www.gsnv.org\/shop\/geometry-of-the-neoproterozoic-continental-break-up-and-implications-for-location-of-nevadan-mineral-belts\/","title":{"rendered":"Geometry of the Neoproterozoic Continental Break-Up, and Implications for Location of Nevadan Mineral Belts"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"<p>ABSTRACT<br \/>\nLinear alignments of ore deposits in northern Nevada define<br \/>\nthe Battle Mountain-Eureka trend on the southwest and the Carlin<br \/>\ntrend on the northeast. Epigenetic sedimentary rock-hosted Au<br \/>\ndeposits dominate the belts, but porphyry systems and hot-spring<br \/>\ndeposits are also present. The belts are proposed to reflect deepcrustal<br \/>\nfault systems, which have no obvious surficial fault expression<br \/>\nbut are marked by subparallel fold hinges at angles to the<br \/>\nregional fold trends. The deep crustal faults cut continental basement<br \/>\ninboard from the North American continental margin, which is<br \/>\ndefined by an initial 87Sr\/86Sr = 0.706 isopleth and by stratigraphic<br \/>\nfacies. The continental margin crosses Nevada with sharp bends in<br \/>\ninferred orientation. A generally NE strike to the margin in southwestern<br \/>\nand northern Nevada is separated by a segment striking NW<br \/>\nthrough western Nevada. It swings abruptly to northerly strikes in<br \/>\nIdaho, whereas in California it has been offset northward by<br \/>\nMesozoic and Tertiary strike-slip faults. The eastern edge of<br \/>\nNeoproterozoic terrigenous clastic rocks deposited during rifting<br \/>\nbroadly parallels the continental margin. Within those terrigenous<br \/>\nclastic rocks, the isopach defining the eastern edge of significant<br \/>\nthickness of clastic rocks exhibits changes in orientation that<br \/>\nbroadly mimic the continental margin, thereby suggesting a structural<br \/>\nrelationship. Beneath the clastic rocks in the underlying continental<br \/>\nbasement, compositional variations indicated by Pb isotopes<br \/>\nand Pb versus Sr isotopic relations are recorded in Mesozoic and<br \/>\nTertiary igneous rocks. Based on strongly correlated Pb and Sr isotopic<br \/>\ncompositions in the igneous rocks, we propose that a thinned,<br \/>\ntransitional continental crust thickens eastward until a boundary<br \/>\nalong the Carlin trend, and the strike extensions southeastward, in<br \/>\neastern Nevada. To the east, Pb and Sr isotopic ratios in plutons are<br \/>\nnot strongly correlated and have much greater variability than in<br \/>\nplutons to the west. The discontinuity at the Carlin trend represents<br \/>\na major crustal compositional change in the basement, which is best<br \/>\ninterpreted to be a fault system. The mineral belts are subparallel to<br \/>\nthe NW-trending edge of continental crust, but at high angles to the<br \/>\nNE-trending segments. A re-entrant in Pb isopleths corresponds to<br \/>\nthe intersection between the NW-striking Battle Mountain-Eureka<br \/>\ntrend and the NE-striking continental margin.<br \/>\nThe geometric relation between the edge of the continental margin<br \/>\nand the orientation of the mineral belts is reconciled in the context<br \/>\nof a rifted margin during continental break-up in the<br \/>\nNeoproterozoic and Early Cambrian. In the model, the Carlin and<br \/>\nBattle Mountain-Eureka trends are related to crustal-scale normal<br \/>\nfault systems, which accommodated thinning of the continental-margin<br \/>\ncrust. The Carlin trend represents the boundary between relatively<br \/>\nintact Proterozoic-Archean crust on the east and thinned, transitional<br \/>\ncontinental crust on the west. The Battle Mountain-Eureka<br \/>\ntrend reflects a major rift fault system within the thinned continental<br \/>\nmargin. Implicit in this model is that the currently NE-striking segments<br \/>\nof the continental margin likely represent paleotransform<br \/>\nfaults along a rifted margin. In the Phanerozoic, the basement faults,<br \/>\nbeing fundamental crustal weaknesses, would influence sedimentation,<br \/>\ndeformation, and hydrothermal fluid circulation patterns if<br \/>\nappropriately oriented.<\/p>\n","protected":false},"featured_media":4051,"comment_status":"closed","ping_status":"closed","template":"","meta":{"pmpro_default_level":""},"product_cat":[154],"product_tag":[],"_links":{"self":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product\/2306"}],"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=2306"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/media\/4051"}],"wp:attachment":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/media?parent=2306"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product_cat?post=2306"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product_tag?post=2306"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}