摘要
江西永平铜矿位于华南怀玉山—北武夷山铜铅锌多金属成矿带内,是赣东北地区除了德兴铜矿外的另一个大型铜矿基地。该矿区存在两种类型的花岗质岩石,一种是花岗岩;另一种是英安斑岩。英安斑岩具有典型斑状结构和石英眼结构,而花岗岩则具有单向固结结构。在化学成分上,两者属于高钾的钙碱性系列岩石,英安斑岩贫硅、富Al、Fe、Mg、Ca,以及具有较大的Na_2O/K_2O(0.02～0.64)等特点;而花岗岩富硅、贫Al、Ca,以及富碱和具有较小的Na_2O/K_2O(0.02～0.03)等特点。两种类型的岩石具有一致的REE配分曲线。它们均富集大离子亲石元素(Ba、Rb、K),亏损高场强元素(Th、Nd、Ta、Ti)以及元素Sr和P,显示了与俯冲作用有关的岩浆作用。在结构和化学成分上,花岗岩则类似于美国Climax斑岩钼(铜)矿成矿斑岩的性质(如具有单向固结结构、较高的分异指数、富Si、贫Al、Ca、富Na_2O+K_2O以及K_2O>Na_2O)。与英安斑岩有关的蚀变作用主要有夕卡岩化、黑云母化、白云母化、绿泥石化和萤石化,而与花岗岩有关的蚀变作用主要是白云母化和萤石化;相应地,与英安斑岩有关的成矿作用主要为铜,而与花岗岩有关的成矿作用则主要为钼。2件辉钼矿样品的Re-Os年龄分别为156.7±2.8Ma和155.7±3.6Ma,表明与花岗岩有关的钼成矿作用发生在156Ma左右。本文认为,永平铜钼矿的成矿地球动力学背景应是由挤压向伸展的转换环境。
The Yongping Cu-Mo deposit is located in the Huaiyushan-North Wuyishan Cu-Pb-Zn polymetallic metallogenic belt in South China. It is another large copper deposit besides the Dexing Cu-Mo deposit in northeastern Jiangxi. Two types of granitic rock occur in the deposit: one is dacite porphyry, and the other is granite. The dacite has a typical porphyritic texture and a quartz eye texture, whereas the granite has unidirectional solidification textures ( UST). Chemically both of them belong to a high-K calc-alkaline suite. Dacite porphyry is poor in Si and rich in Al, Fe, Mg and Ca, with Na2O < K2O and Na2O/K2O = 0.02 similar to 0. 64; whereas granite is rich in Si and alkalis and poor in Al and Ca, with Na2O < K2O and Na2O/K2O = 0.02 similar to 0. 03. Both of them have similar BEE distribution patterns. Primitive mantle-normalized BEE patterns of the two types of rock show subduction-related features, i.e., LILE (Ba, Rb, K) enrichment and HFSE (Th, Nb, Ta, Ti) and Sr and P depletion. In terms of the textures and chemical composition, the granitic rocks show the characteristics similar to those of mineralized porphyry related to Climax-type porphyry Mo (Cu) deposits in North America (e. g. unidirectional solidification textures, higher differentiation index, Si enrichment, Al and Ca depletion and Na2O +K2O and K2O > Na2O), indicating a significant potentiality for Mo mineralization. The alterations related to dacite porphyry are dominantly skarnization, biotitization, muscovitization, sericitization, chloritization and floritization, of which muscovitization and floritization are associated with granitic rocks. Accordingly, the mineralization associated with dacite porphyry is copper, while the mineralization associated with granite is molybdenite mineralization. Two molybdenite samples from quartz and molybdenite veins in granite yield Re-Os ages of 156.7 +/- 2.8 and 155.7 +/- 3.6 Ma respectively, suggesting that the molybdenite mineralization related to granitic rocks took place at similar to 156 Ma. The Yongping d
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第10期2353-2365,共13页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40403006)
国家自然科学基金重点项目(40434011)
留学人员短期回国讲学专项(40610404013)
日本学术振兴协会科学研究基金资助成果.
关键词
单向固结结构
岩石化学
岩浆-热液转换
铜钼成矿作用
构造体制转换
永平
江西
unidirectional solidification texture (UST)
geochemistry
magmatic-hydrothermal transition
climax Cu-Mo mineralization
tectonic regime transition
Yongping
Jiangxi
