滇西大理地区岩体黑云母化学特征及其对成矿的指示意义  

Biotites chemical characteristics from Dali district,Western Yunnan and geological significance

作　　者：郑瑜林 崔猛 张长青[3] 董云涛 王瑞[2] 伏东红 朱学兵 方永春 ZHENG Yulin;CUI Meng;ZHANG Changqing;DONG Yuntao;WANG Rui;FU Donghong;ZHU Xuebin;FANG Yongchun(School of Architectual Engineering,Quzhou University,Quzhou 324000,Zhejiang,China;Yunnan Gold&Mining Group Co.,Ltd.,Kunming 650000,Yunnan,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Key Laboratory of Mineral-ization and Resource Evaluation,Ministry of Natural Resources,Beijing 100037,China)

机构地区：[1]衢州学院建筑工程学院,浙江衢州324000 [2]云南黄金集团股份有限公司,云南昆明650000 [3]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《矿产勘查》2025年第2期267-281,共15页Mineral Exploration

基　　金：衢州学院博士科研启动项目(KYQD005223007);深地资源项目(2016YFC0600305);国家自然科学基金(41602103);中国地质调查局项目(DD20190182)联合资助。

摘　　要：金沙江—哀牢山富碱斑岩带内发育众多成岩时代集中于37~33 Ma的富碱斑岩,其中部分岩体(富矿岩体)与带内Cu-Au-Mo矿化关系密切,部分岩体(贫矿岩体)尚未发现矿化,前人研究多集中于二者在岩石地球化学上的差异,缺乏矿物地球化学特征上的对比。本文以北衙富矿石英正长斑岩、马厂箐富矿花岗斑岩、白莲村贫矿正长斑岩和松桂贫矿正长斑岩为研究对象,对富矿与贫矿岩体中的黑云母进行了电子探针分析,计算了富矿与贫矿岩体岩浆流体性质、岩浆氧逸度,揭示了富矿与贫矿岩体岩石成因与源区性质,讨论了富矿岩体与贫矿岩体在矿物化学尺度上的差异。黑云母主量元素分析结果显示,富矿与贫矿岩体中的黑云母均为岩浆成因,且富镁w(MgO)范围8.86%~15.54%,Fe^(2+)/(Mg+Fe^(2+))比值范围0.29~0.53,属于镁质黑云母。富矿与贫矿岩体中的黑云母具有显著不同于S型和A型花岗岩的Mg/(Fe+Mg)、log(X_(F)/X_(OH))和Al~(VI)值,指示母岩浆具有I型花岗岩的特征,均来自新生下地壳角闪岩的部分熔融。富矿岩体中的黑云母IV(F)(1.21~1.71,平均1.43)、IV(Cl)(-4.25~-3.03,平均-3.84)低于贫矿岩体中的黑云母IV(F)(1.61~1.91,平均1.76)、IV(Cl)(-4.61~-3.29,平均-3.74),表明富矿岩体中的云母更加富集F和Cl。富矿岩浆流体相比于贫矿岩浆流体具有更低的log(fH_(2)O/fHF)^(fluid)值(富矿:3.80~4.54,平均4.1;贫矿:3.99~4.60,平均4.28)和略高的log(fH_(2)O/fHCl)^(fluid)值(富矿:2.88~4.20,平均3.64;贫矿3.02~4.18,平均3.63),表明贫矿岩浆流体较富矿岩浆流体显示出更为富集的HCl,但富矿岩体早期岩浆氧逸度远高于贫矿岩体,由此看出,岩浆流体Cl含量高低并不是控制岩体成矿的第一决定性因素,岩体含矿与否的因素并不是单一的因素控制,而是多种因素综合作用的结果,氧逸度的高低对岩体的成矿与否更为重要。综上,黑云母指示地质过程较为有效,但是部分A series of 37-33 Ma alkali-rich porphyries developed along the Jinshajiang-Ailaoshan alkali-rich porphyry belt during the Indo-Asian continental collision period,some of these porphyries(fertile)are closely relat-edto regional Cu-Au-Mo mineralization,and the others are barren,Previous studies have mostly focused on the whole rock geochemistry of both porphyries,and the differences in mineral geochemistry between fertile and barren porphyry are still unclear.This paper focuses on the Beiya fertile quartz syenite porphyry,Machangqing fertile gran-ite porphyry,Bailiancun and Songgui barren syenite porphyry.EMPA analysis was conducted on biotite,and the properties of magma^(fluid)and magma oxygen fugacity were calculated.The rock genesis and source properties of fer-tile and barren were revealed,finally discussed the differences in mineral chemical between fertile and barren por-phyries.The analysis of major elements in biotites shows that the biotites in both porphyries are magmatic origin and rich in magnesium,with MgO(8.86%-15.54%),Fe^(2+)/(Mg+Fe^(2+))(0.29-0.53)belonging to magnesian biotite.The biotite in fertile and barren porphyries has significantly different Mg/(Fe+Mg),log(X_(F)/XOH),and AlVI values from S-type and A-type granites,indicating that the parent magma has the characteristics of I-type granites,both of which are derived from partial melting of lower crustal amphibolites.The biotite IV(F)(1.21-1.71,average 1.43)and IV(Cl)(-4.25 to 3.03,average-3.84)in the fertile porphyry are lower than those in the barren porphyry(1.61-1.91,average 1.76)and IV(Cl)(-4.61 to 3.29,average-3.74),indicating that the mica in the fertile porphyry is more enriched in F and Cl.Lower log(fH_(2)O/fHF)^(fluid)values and higher log(fH_(2)O/fHCl)^(fluid)values in fertile porphyry(fertile:3.80-4.54,average 4.1,2.88-4.20,average 3.64;barren:3.99-4.60,average 4.28,3.02-4.18,average 3.63),indicating that magma^(fluid)s of barren porphyry show more enriched HCl than fertile porphyry.However,the oxygen fugacity of early magma in fer

关 键 词：金沙江—哀牢山富碱斑岩带 黑云母 岩浆流体性质 氧逸度 岩石成因 

分 类 号：P571[天文地球—矿物学]