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δ^(13)C_(PDB)=-3.7‰~1.4‰,平均值-0.1‰,δ^(18)O_(SMOW)=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δ^(13)C_(PDB)=-3.7‰~0.1‰(均值为-1.5‰),δ^(18)O_(SMOW)=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δ^(13)C_(PDB)-δ^(18)O_(SMOW)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。
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 δ^13CPDB=-3.7‰-1.4‰ with an average value of -0.1‰ and δ^18OSMOW=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 δ^13CPDB=-3.7‰-0.1‰ （a mean value of -1.5‰） and δ^18OSMOW=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 δ^13CPDB-δ^18OSMOW 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-super
出处
《地质与勘探》
CAS
CSCD
北大核心
2016年第2期228-238,共11页
Geology and Exploration
基金
国家危机矿山接替资源勘查项目(编号20089943)
云南铜业(集团)股份有限公司重点科技项目资助
关键词
C、O同位素组成
成矿流体
成因类型
易门铜厂
C-O isotopic compositions, ore-forming fluids, genetic types, Yimen Tongchang
