摘要
扬子地台西缘富碱斑岩带以往只有为数不多的中-小型斑岩铜钼矿和中-大型铅矿床,近年发现了较多的大、中、小型金(银)矿床,预示该区有较好的找矿前景。本文系统收集和分析前人研究成果,总结归纳该区带富碱斑岩的岩石学、岩石化学、岩石蚀变、稀土元素配分、包裹体地球化学、稳定同位素及含矿与非含矿富碱斑岩区别等特征,认为该区带富碱斑岩主要由富碱花岗斑岩类和碱性正长斑岩类组成,为喜马拉雅早中期的浅成-超浅成侵入体,岩石的Si2O含量偏低,富碱高钾,与澳大利亚“A”型花岗岩相似;岩体间稀土总量、轻重稀土元素比值及δEu值基本近似,稀土元素组成模式曲线均为向右陡倾斜的平滑曲线,显示成岩成矿物质来源于上地幔与下地壳,两类富碱斑岩的岩浆演化和成因具有同一性。通常在岩体规模较小、形态复杂、碱质相应偏低,富含Cu、Mo、Pb、Zn、Au、Ag等矿化元素和Li、Rb、Cs等稀土碱金属元素,蚀变类型多、蚀变较强、分带好,稀土元素(ΣREE)总量偏高的岩体中,有望找到大型的Cu、Mo、Pb、Zn、Au、Ag矿床。
Along the alkali-rich porphyry belt on the western margin of the Yangtze platform,only a few medium-small size porphyry Cu-Mo deposits and medium-large size Pb deposits were previously found;nevertheless,quite a number of large,medium and small size Au(Ag)deposits have been discovered in recent years,which implies fairly good prospect in search for mineral deposits.The authors systematically collected and analyzed the achievements obtained by previous researchers,summed up such characteristics of alkali-rich porphyries in this area as petrology,petrochemistry,rock alteration,REE partitioning,inclusion geochemistry,stable isotopes and the difference between ore-bearing porphyries and barren ones.On such a basis,the authors hold that that the alkali-rich porphyries in this belt are composed mainly of alkali-rich granite porphyries and alkaline orthophyre,and belong to hypabyssal-ultrahypabyssal intrusive bodies of early-middle Himalayan period.The rocks have somewhat lower Si2O content and rich alkali and high potassium,similar to things of“A”type granites in Australia.The intrusive bodies have basically similar REE total content,LREE/HREE ratios andδEu values,and their REE pattern curves are all steeply right-oblique smooth curves,suggesting that the rock-forming and ore-forming materials were derived from the upper mantle and the lower crust;in addition,the magmatic evolution and genesis of the two types of alkali-rich porphyries show identity.Generally speaking,large size Cu,Mo,Pb,Zn,Au and Ag deposits are likely to be found in the intrusive bodies characterized by comparatively small size,complex shape,somewhat lower alkali,richness of ore-forming elements such as Cu,Mo,Pb,Zn,Au ang Ag and REE alkaline metallic elements like Li,Rb and Cs,varied alteration types,strong alteration,obvious zoning and somewhat higher REE total content(ΣREE).
作者
张道红
张学书
杨艳
严健
杨平
ZHANG Dao-hong;ZHANG Xue-shu;YANG Yan;YAN Jian;YANG Ping(Yunnan Nonferrous Metals Geological Bureau,Kunming,Yunnan 650051;Yunnan Bureau of Geological Survey,Kunming,Yunnan 650051;Institute of Geology,Yunnan Nonferrous Metals Geological Bureau,Kunming,Yunnan 650216)
出处
《地球学报》
CAS
CSCD
北大核心
2013年第S01期168-176,共9页
Acta Geoscientica Sinica
基金
云南省三年地质找矿行动计划专项经费项目(编号:20090681)资助。
关键词
斑岩型铜钼金矿
富碱斑岩
岩石学及地球化学特征
杨子地台西缘
porphyry Cu-Mo-Au deposit
alkali-rich porphyry
petrology and geochemistry
western margin of the Yangtze platform
