| 肖术安.云南易门铜厂铜矿床C、O同位素组成及其地质意义[J].地质与勘探,2016,52(2):228-238 |
| 云南易门铜厂铜矿床C、O同位素组成及其地质意义 |
| Carbon and oxygen isotopic compositions in the Tongchang copper deposit of Yimen, Yunnan and their geological implications |
| 投稿时间：2015-04-15 修订日期：2016-01-26 |
| DOI： |
| 中文关键词: C、O同位素组成 成矿流体 成因类型 易门铜厂 |
| 英文关键词: C-O isotopic compositions, ore-forming fluids, Genetic types, Yimen, Tongchang |
| 基金项目:国家危机矿山接替资源勘查项目（编号20089943）及云南铜业（集团）股份有限公司重点科技项目资助 |
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| 中文摘要: |
| 易门铜厂矿床是滇中易门铜矿带中的Cu品位较低的大型矿床，是矿带中的一种代表性矿床。矿区发育沉积-成岩型铜矿（铜厂式）和热液脉状铜矿（大尖山式）两种矿（化）体，成矿地质作用较特殊。本文系统分析两类矿体和赋矿碳酸盐地层的C、O同位素组成。结果表明，铜厂式矿石中白云石的δ13CPDB=-3.7‰~1.4‰，平均值-0.1‰，δ18OSMOW=19.7‰~21.7‰，平均值20.8‰，与赋矿碳酸盐地层（落雪组）中的白云石C、O同位素组成一致，均在正常海相沉积碳酸盐岩的范围，且受成岩期后作用的影响小，具有典型的沉积-成岩成因标志。尖山式矿体的脉石矿物方解石的δ13CPDB=-3.7‰~0.1‰ （均值为-1.5‰），δ18OSMOW=11.9‰~17.0‰（均值为14.1‰），与沉积-成岩型矿体和赋矿碳酸盐地层的C、O同位素组成明显不同，在δ13CPDB-δ18OSMOW图上集中于岩浆碳酸岩与海相碳酸盐岩之间的狭小范围内，指示其成矿流体与幔源或深部岩浆活动有关，为壳-幔混合流体。其中壳源组分可能主要由矿区碳酸盐地层提供，而幔源组分则可能与晋宁-澄江期基性岩浆活动过程中的去气作用有关。C、O同位素组成证据说明，铜厂矿区层状铜矿和脉状铜矿的成矿作用类型不同，成矿流体也不具同源性，是典型的沉积-成岩型+热液叠加型矿床。 |
| 英文摘要: |
| The Tongchang copper deposit in Yimen county, a large one of low grade in within the Yimen copper ore belt in middle Yunnan Province, is a representative deposit. Two kinds of ore bodies (or mineralized bodies)-sedimentary-diagenetic copper ore (Tongchang type) and hydrothermal vein-like copper ore (Dajianshan type) are present in the ore district with special geological metallogenesis. This paper analyzes these two bodies as well as isotopic composition of carbon and oxygen in their ore-bearing carbonate strata. The results suggest that dolomite in Tongchang-type ore shows δ13CPDB=-3.7‰~1.4‰ with an average value of -0.1‰ and δ18OSMOW=19.7‰~21.7‰ with an average value of 20.8‰, which is consistent with carbon and oxygen isotope composition of dolomite in the ore-bearing carbonate formation (Luoxue Formation). Both of them are within the range of normal marine sedimentary carbonatite, and little influenced by the process after the diagenetic period, showing a characteristic sedimentary-diagentic origin sign. Calcite as a gangue mineral in the Jianshan-type ore body displays δ13CPDB=-3.7‰~0.1‰ (a mean value of -1.5‰) and δ18OSMOW=11.9‰~17.0‰ (a mean value of 14.1‰), which is obviously different from the carbon and oxygen isotope composition of sedimentary-diagentic ore body and ore-bearing carbonate formation. On the δ13CPDB-δ18OSMOW diagram, these data are gathered within a narrow scope between magmatic carbonatite and marine carbonatite, indicating the metallogenic fluids related with mantle source or deep magma activity are crust-mantle mixed fluids. Therefore, crust-derived components may be mainly provided by carbonate formation in the ore area; while mantle-derived constitutes are probably associated with degasification in the process of basic magma action during Jinning-Chengjiang stage. Such evidence as isotopic composition of carbon and oxygen shows that the Tongchang mineral deposit is typically sedimentary-diagenetic type + hydrothermal-superimposing type for that stratiform and veined copper ores are produced by different metallogenetic processes in the Tongchang orefield, and ore-forming fluids are not derived from a same source. |
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