{"id":2498,"date":"2019-10-02T19:54:17","date_gmt":"2019-10-02T19:54:17","guid":{"rendered":"https:\/\/www.gsnv.org\/shop\/identifying-magmatic-versus-amagmatic-sources-for-modern-geothermal-systems-associated-with-epithermal-mineralization-using-noble-gas-geochemistry\/"},"modified":"2020-02-24T18:17:55","modified_gmt":"2020-02-24T18:17:55","slug":"identifying-magmatic-versus-amagmatic-sources-for-modern-geothermal-systems-associated-with-epithermal-mineralization-using-noble-gas-geochemistry","status":"publish","type":"product","link":"https:\/\/www.gsnv.org\/shop\/identifying-magmatic-versus-amagmatic-sources-for-modern-geothermal-systems-associated-with-epithermal-mineralization-using-noble-gas-geochemistry\/","title":{"rendered":"Identifying magmatic versus amagmatic sources for modern geothermal systems associated with epithermal mineralization using noble gas geochemistry"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"<p>Modern geothermal systems in the Great Basin of California and Nevada typically<br \/>\nare characterized as the result of a focused and identifiable magmatic heat source<br \/>\nor of a regionally dispersed amagmatic heat flux. Young (< 7Ma), economically viable\nepithermal Au deposits are closely associated with some modern, presumably\namagmatic geothermal systems. This close spatial association of theAu deposits to the\nmodern geothermal systems has led to speculation of an amagmatic origin for the deposits\nand that the modern geothermal systems could be actively precipitating Au in\nthe subsurface. In an effort to clarify the possible role of amagmatic geothermal systems\nas the source of young to modern epithermal Au mineralization, noble gas and\nfluid chemistry samples were collected from active, amagmatic geothermal systems in\nNevada (Wabuska, San Emidio, Brady Hot Springs, Humboldt House [Florida Canyon],\nand Soda Lake) as well as modern magmatic geothermal systems in California\n(Clear Lake, Wilber Springs, Lassen Volcanic National Park and Mammoth Mountain).\nCalculated silica geothermometery on the fluids from the Nevada geothermal\nsystems agrees well with the measured down-hole temperatures from the reservoirs.\nThe calculated reservoir temperatures of these systems span the range of 150 to\n210\u00b0C, exceptWabuska which yields a temperature of 135\u00b0C. Noble gas compositions\nfrom both magmatic or amagmatic systems are characterized by atmospherically derived\ncomponents that have mixed with deeper non-atmospheric sources. Helium isotopic\ndata, after correction for atmospheric components (excess He), shows a dominance\nof crustal helium (87 to 97 percent of the excess He component) supporting an\namagmatic origin, except in the case of the Soda Lake, where almost 54 to 59 percent\nof the excess He is mantle derived. Comparison of the He data with Au concentrations\nin fluid samples shows a positive correlation between gold and the mantle helium content\nin both the magmatic and amagmatic systems. This relationship is at odds with\ncurrent theories that the modern, amagmatic geothermal systems are responsible for\nsubstantialAu transport that resulted in the spatially associated young epithermal deposits.\nThis postulate is further supported from noble and bulk gas compositions from\nfluid inclusions in silica precipitates from Florida Canyon and Dixie Valley.\n<\/p>\n","protected":false},"featured_media":4574,"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\/2498"}],"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=2498"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/media\/4574"}],"wp:attachment":[{"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/media?parent=2498"}],"wp:term":[{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product_cat?post=2498"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/www.gsnv.org\/wp-json\/wp\/v2\/product_tag?post=2498"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}