安徽桂花冲花岗闪长斑岩中黑云母成分特征及地质意义
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摘要
安徽桂花冲铜矿位于繁昌盆地与铜陵隆褶带的过渡地带,是一新发现的斑岩-矽卡岩复合型铜矿床,成矿时代为白垩纪早期。矿区岩浆岩主要为花岗闪长斑岩,为探究岩浆的起源、成岩物理化学条件,对其斑晶黑云母进行系统的显微岩相学观察和矿物化学研究。电子探针分析结果表明,黑云母MgO,TFeO,Al_2O_3和TiO_2的质量分数分别为14.15%~15.60%,15.17%~16.41%,12.94%~13.49%和3.84%~4.63%,为富镁贫铁低铝高钛,属镁质黑云母。岩石成分、结构、构造等特征表明,该斑岩体属于壳幔混源的Ⅰ型花岗岩,岩浆结晶温度在750℃~780℃之间,氧逸度f(O_2)为1×10~(-12)Pa~1×10~(-10) Pa。通过黑云母全铝压力计算得其压力为49.96 MPa~72.38 MPa,对应的岩浆房深度为1.89km~2.74km,属超浅岩浆房。岩体附近火山岩的存在,是桂花冲地区形成斑岩型铜矿的重要影响因素。
The Guihuachong copper deposit is a porphyry-skarn composite type copper deposit newly discovered and formed in the Early Cretaceous,which is located in the transition zone between Fan chang basin and Tongling transitional belt.In this paper,for the study of the origin of magma,diagenesis,physical and chemical conditions,petrographic and mineralogical characteristics of the biotites in Guihuachong granodiorite are investigated,and their forming conditions and the geological significances are discussed.Electron microprobe analysis(EPMA)of the biotites show that the contents of MgO,TFeO,Al_2O_3 and TiO_2 in biotite are 14.15%~15.60%,15.17%~16.41%,12.94% ~13.49% and 3.84% ~4.63%,respectively,which belong to Mg-biotites,relatively rich in Mg and Ti and poor in Fe and Al.According to the characteristics of biotite composition,The Guihuachong granodiorite belongs to I-type granite.The crystallization temperature(T)and oxygen fugacity f(O_2)of the biotites are 750 ℃~780 ℃ and 1×10~(-12) Pa~1×10~(-10) Pa,respectively.The solidification pressure(P)of the biotites is 49.96 MPa~72.38 MPa and the depth of magma chamber is 1.89km~2.74 km,which belongs to the shallow magma chamber.The volcanic rock is an important influence factor for the formation of porphyry copper deposits in the Guihuachong area.
The Guihuachong copper deposit is a porphyry-skarn composite type copper deposit newly discovered and formed in the Early Cretaceous,which is located in the transition zone between Fan chang basin and Tongling transitional belt.In this paper,for the study of the origin of magma,diagenesis,physical and chemical conditions,petrographic and mineralogical characteristics of the biotites in Guihuachong granodiorite are investigated,and their forming conditions and the geological significances are discussed.Electron microprobe analysis(EPMA)of the biotites show that the contents of MgO,TFeO,Al_2O_3 and TiO_2 in biotite are 14.15%~15.60%,15.17%~16.41%,12.94% ~13.49% and 3.84% ~4.63%,respectively,which belong to Mg-biotites,relatively rich in Mg and Ti and poor in Fe and Al.According to the characteristics of biotite composition,The Guihuachong granodiorite belongs to I-type granite.The crystallization temperature(T)and oxygen fugacity f(O_2)of the biotites are 750 ℃~780 ℃ and 1×10~(-12) Pa~1×10~(-10) Pa,respectively.The solidification pressure(P)of the biotites is 49.96 MPa~72.38 MPa and the depth of magma chamber is 1.89km~2.74 km,which belongs to the shallow magma chamber.The volcanic rock is an important influence factor for the formation of porphyry copper deposits in the Guihuachong area.
引文
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[17]Wones D,Eugster H.Stability of biotite:experiment,theory and application.Am.Mineral,1965,50(9):1 228-1 273.
[18]周作侠.湖北丰山洞岩体成因探讨[J].岩石学报,1986,2(1):59-70.
[19]马昌前,杨坤光,唐仲华,等.花岗岩类与岩浆动力学-理论方法及鄂东花岗岩类例析[M].武汉:中国地大出版社,1994,210-212.
[20]Etsuo Uchida,Sho Endo,Mitsutoshi Makino.Relationship Between Solidification Depth of Granitic Rocks and Formation of Hydrothermal Ore Deposits[J].Resource Geology,2007,57(1):47-56.
[21]熊小林,石满全,陈繁荣.浅成—次火山岩黑云母Cu,Au成矿示踪意义[J].矿床地质,2001,21(2):107-111.
[22]刘学龙,李文昌,尹光侯.云南格咱岛弧印支期地壳隆升与剥蚀及其地质意义:来自黑云母矿物压力计的证据[J].现代地质,2013,27(3):537-545.
[2]杜杨松,李顺庭,曹毅,等.安徽铜陵铜官山矿区中生代侵入岩的形成过程—岩浆底侵、同化混染和分离结晶[J].现代地质,2007,21(1):71-77.
[3]常印佛,刘学圭.关于层控式矽卡岩型矿床—以安徽省内下扬子坳陷中一些矿床为例[J].矿床地质,1983,(1):11-20.
[4]常印佛,刘湘培,吴言昌.长江中下游铜铁成矿带[M].北京:地质出版社,1991,1-238.
[5]姚凤良,孙丰月.矿床学教程[D].北京:地质出版社,2006.
[6]孟祥金,吕庆田,杨竹森,等.长江中下游铜陵及邻区中生代中酸性侵入岩地球化学特征及其深部岩浆作用探讨[J].地质学报,2011,85(5):757-777.
[7]吴才来,陈松永,史仁灯,等.铜陵中生代中酸性侵入岩特征及成因[J].地球学报,2003,24(1):41-48.
[8]岳紫龙,杜杨松,曹毅,等.铜陵桂花冲花岗闪长斑岩地球化学特征、锆石U-Pb年龄及其地质意义[J].矿物岩石,2015,35(1):82-90.
[9]El Sheshtawi Y A,Salem A K A,Aly M M.The geochemistry of ferrous biotite and petrogenesis of Wadi E-l Sheikh granitoid rocks Southwestern Sinai,Egypt[J].African Earth Sci,1993,16(4):489-498..
[10]黄文明.安徽省南陵县桂花冲铜金多金属矿矿床地质特征[D].武汉:中国地质大学,2011.
[11]蒋其胜,赵自宏,黄建满.安徽南陵姚家岭铜铅锌矿床的发现及意义[J].中国地质,2008,35(2):314-321.
[12]林文蔚,彭丽君.由电子探针分析数据估算角闪石、黑云母中的Fe3+、Fe2+[J].长春地质学院院报,1994,24(2):155-162.
[13]周瑄若,任进.长江中下游中生代花岗岩[M].北京:地质出社,1994,71-73.
[14]Kanisawa S.Chemical characteristics of biotite and horn-blende of the late Mesozoic to early Tertiary granitic rocks in Japan[C].Proc.7thCPPP Meeting at Toyama,1977,194-202.
[15]Foster M D.Interpretation of the composition of trioctahedral micas[J].U.S.Geol.Surey,Prof.Paper,1960,354:11-49.
[16]张有军,梁文天,罗先熔,等.秦岭造山带光头山岩体群黑云母地球化学特征及成岩意义[J].矿物岩石,2015,35(1):100-108.
[17]Wones D,Eugster H.Stability of biotite:experiment,theory and application.Am.Mineral,1965,50(9):1 228-1 273.
[18]周作侠.湖北丰山洞岩体成因探讨[J].岩石学报,1986,2(1):59-70.
[19]马昌前,杨坤光,唐仲华,等.花岗岩类与岩浆动力学-理论方法及鄂东花岗岩类例析[M].武汉:中国地大出版社,1994,210-212.
[20]Etsuo Uchida,Sho Endo,Mitsutoshi Makino.Relationship Between Solidification Depth of Granitic Rocks and Formation of Hydrothermal Ore Deposits[J].Resource Geology,2007,57(1):47-56.
[21]熊小林,石满全,陈繁荣.浅成—次火山岩黑云母Cu,Au成矿示踪意义[J].矿床地质,2001,21(2):107-111.
[22]刘学龙,李文昌,尹光侯.云南格咱岛弧印支期地壳隆升与剥蚀及其地质意义:来自黑云母矿物压力计的证据[J].现代地质,2013,27(3):537-545.
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