中文版 | English
Arid
DOI10.1130/GES02086.1
Porphyry copper deposit formation in arcs: What are the odds?
Richards, Jeremy P.
通讯作者Richards, JP (corresponding author), Laurentian Univ, Mineral Explorat Res Ctr, Harquail Sch Earth Sci, Sudbury, ON P3E 2C6, Canada.
来源期刊GEOSPHERE
ISSN1553-040X
出版年2022
英文摘要Arc magmas globally are H2O-CI-S-rich and moderately oxidized (Delta FMQ = +1 to +2) relative to most other mantle-derived magmas (Delta FMQ <= 0). Their relatively high oxidation state limits the extent to which sulfide phases separate from the magma, which would otherwise tend to deplete the melt in chalcophile elements such as Cu (highly siderophile elements such as Au and especially platinum-group elements are depleted by even small amounts of sulfide segregation). As these magmas rise into the crust and begin to crystallize, they will reach volatile saturation, and a hydrous, saline, S-rich, moderately oxidized fluid is released, into which chalcophile and any remaining siderophile metals (as well as many other water-soluble elements) will strongly partition. This magmatic-hydrothermal fluid phase has the potential to form ore deposits (most commonly porphyry Cu +/- Mo +/- Au deposits) if its metal load is precipitated in economic concentrations, but there are many steps along the way that must be successfully negotiated before this can occur. This paper seeks to identify the main steps along the path from magma genesis to hydrothermal mineral precipitation that affect the chances of forming an ore deposit (defined as an economically mineable resource) and attempts to estimate the probability of achieving each step. The cumulative probability of forming a large porphyry Cu deposit at any given time in an arc magmatic system (i.e., a single batholith-linked volcanoplutonic complex) is estimated to be similar to 0.001%, and less than 1/10 of these deposits will be uplifted and exposed at shallow enough depths to mine economically (0.0001%). Continued uplift and erosion in active convergent tectonic regimes rapidly remove these upper-crustal deposits from the geological record, such that the probability of finding them in older arc systems decreases further with age, to the point that porphyry Cu deposits are almost nonexistent in Precambrian rocks. A key finding of this paper is that most volcanoplutonic arcs above subduction zones are prospective for porphyry ore formation, with probabilities only falling to low values at late stages of magmatic-hydrothermal fluid exsolution, focusing, and metal deposition. This is in part because of the high threshold required in terms of grade and tonnage for a deposit to be considered economic. Thus, the probability of forming a porphyry-type system in any given arc segment is relatively high, but the probability that it will be a large economic deposit is low, dictated to a large extent by mineral economics and metal prices.
类型Article
语种英语
开放获取类型gold
收录类别SCI-E
WOS记录号WOS:000729389100001
WOS关键词CALC-ALKALINE DIFFERENTIATION ; MAGMATIC-HYDROTHERMAL FLUIDS ; SUBDUCTION ZONE MAGMAS ; EPITHERMAL AU-AG ; ABLATION ICP-MS ; CU-AU ; VOLCANIC-ROCKS ; ATACAMA-DESERT ; NORTHERN CHILE ; TRACE-ELEMENT
WOS类目Geosciences, Multidisciplinary
WOS研究方向Geology
资源类型期刊论文
条目标识符http://119.78.100.177/qdio/handle/2XILL650/374595
作者单位[Richards, Jeremy P.] Laurentian Univ, Mineral Explorat Res Ctr, Harquail Sch Earth Sci, Sudbury, ON P3E 2C6, Canada
推荐引用方式
GB/T 7714		 Richards, Jeremy P.. Porphyry copper deposit formation in arcs: What are the odds?[J],2022.
APA Richards, Jeremy P..(2022).Porphyry copper deposit formation in arcs: What are the odds?.GEOSPHERE.
MLA Richards, Jeremy P.."Porphyry copper deposit formation in arcs: What are the odds?".GEOSPHERE (2022).
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