| 云南普朗超大型斑岩铜矿床含矿斑岩成因及其成矿意义 |
| Received:May 11, 2013 Revised:February 26, 2014 点此下载全文 |
| 引用本文：CAO Kang,XU JiFeng,CHEN JianLin,HUANG XiaoXiao,REN JiangBo.2014.Origin of porphyry intrusions hosting superlarge Pulang porphyry copper deposit in Yunnan Province：Implications for metallogenesis[J].Mineral Deposits,33(2):307~322 |
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| Author Name | Affiliation | E-mail | | CAO Kang | Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Isotope Geochemistry, Guangzhou 510640, Guangdong, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | XU JiFeng | Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Isotope Geochemistry, Guangzhou 510640, Guangdong, China | jifengxu@gig.ac.cn | | CHEN JianLin | Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Isotope Geochemistry, Guangzhou 510640, Guangdong, China | | | HUANG XiaoXiao | Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, State Key Laboratory of Isotope Geochemistry, Guangzhou 510640, Guangdong, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | REN JiangBo | Guangzhou Marine Geological Survey, Guangzhou 510075, Guangdong, China | |
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| 基金项目:本文得到国家重点基础研究发展计划“973”项目（编号：2009CB421004）的资助 |
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| 中文摘要:普朗超大型斑岩铜矿床位于三江特提斯构造域义敦弧南部的中甸弧内，形成于晚三叠世甘孜-理塘大洋板片向西俯冲的消减带上。与成矿作用密切相关的石英闪长岩和石英二长岩具有相似的化学组成，w（SiO2）>61%，w（Al2O3）为11.28%~19.12%，w（MgO）为1.98%~4.04%，Na2O/K2O比值介于0.3~2.4（平均0.8）；富集大离子亲石元素（Rb、Sr、Ba）而亏损高场强元素（Nb、Ta、Zr），具有较高的Sr/Y（27~63）和La/Yb（14~31）比值，较明显的负Eu异常，在Y-Sr/Y和Yb-La/Yb图解中，部分样品落入埃达克岩范围内，另一些样品则落入正常弧钙碱性岩石范围。普朗含矿斑岩部分样品的埃达克岩地球化学属性可能与以下地质-地球化学过程有关：晚三叠世甘孜-理塘大洋板片向西俯冲时发生脱挥发分作用导致上覆地幔楔遭受流体交代，被流体交代的地幔楔随后发生部分熔融形成正常拉斑玄武质-钙碱性岩浆，这种钙碱性岩浆在岩浆房中或侵位过程中发生角闪石、斜长石和磷灰石等矿物的分离结晶作用形成埃达克质石英闪长岩或石英二长岩。普朗含矿斑岩中黑云母和角闪石斑晶的广泛发育表明原始岩浆是富水的，这种富水环境促进角闪石的大量结晶而抑制部分斜长石的结晶，导致残余岩浆的Sr/Y比值增加，从而使部分岩石样品具有埃达克岩的地球化学特征。这种富水的原始岩浆有利于后期岩浆热液体系的形成及铜等金属元素向流体相中分配转移，并最终形成普朗超大型斑岩铜矿床。 |
| 中文关键词:地球化学 分离结晶 斑岩铜矿 部分熔融 埃达克岩 普朗 |
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| Origin of porphyry intrusions hosting superlarge Pulang porphyry copper deposit in Yunnan Province：Implications for metallogenesis |
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| Abstract:The superlarge Pulang porphyry copper deposit is located in northwestern Yunnan Province. Tectonically, it lies in Zhongdian arc in the southern part of the Yidun arc that was formed as a result of the westward subduction of the Garze-Litang ocean crust in Late Triassic. Ore-related quartz diorite and quartz monzonite from the Pulang porphyritic intrusive complex are characterized by w(SiO2)>61%, w(Al2O3) ranging from 11.28% to 19.12%, w(MgO) from 1.98% to 4.04% (higher in quartz diorite), enrichment of large ion lithosphile elements (e.g., Rb, Sr, Ba) and depletion of high field-strength elements (e.g., Nb, Ta, Zr) as well as relatively high Sr/Y (27~63) and La/Yb ratios (14~31), with distinct negative Eu anomalies. Some samples fall into the adakite field whereas the others into the normal arc magmas field in the Y-Sr/Y and Yb-La/Yb diagrams. The adakitic affinity of the Pulang ore-bearing porphyries can be interpreted as follows: in late Triassic, dehydration of the westward subducting Garze-Litang ocean crust produced solute-rich aqueous fluids resulting in metasomatization of the overlying mantle wedge, and its partial melting formed basaltic magmas that had experienced fractionation and crystallization of an assemblage consisting of amphibole, plagioclase and apatite in the magma chamber or during their ascent to generate the Pulang ore-bearing porphyries. The abundance of biotite and amphibole phenocrysts in the ore-bearing porphyries indicates that the primitive magmas were hydrous and facilitated fractionation of amphibole and suppression of plagioclase crystallization, a process well explaining the high Sr/Y ratios observed in some samples. The hydrous primitive magmas contributed to the formation of the magmatic-hydrothermal system and the transport of metal elements (e.g., Cu, Au) into the fluid phase. Further ascending of such magmas led to the exsolution of vast ore-forming fluids that finally produced the Pulang porphyry copper deposit at the shallow crust level. |
| keywords:geochemistry fractionation and crystallization porphyry copper deposit partial melting adakite Pulang |
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