安徽铜陵天鹅抱蛋山石英闪长岩岩石学和矿物学特征及其地质意义
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摘要
天鹅抱蛋山石英闪长岩与天马山矽卡岩型硫金矿床具有密切的成因关系,通过对闪长岩进行岩相学观察和详细的矿物化学分析来探讨岩体的形成条件及其地质意义。本区闪长岩中斜长石主要为更长石(An=23~30)和中长石(An=31~38),具有正环带结构,指示岩体在形成过程中经历快速抬升的地质作用。早期角闪石为浅闪石,结晶压力为301 MPa~504 MPa,对应的岩体侵位深度为9.9km~16.6km,结晶温度为721℃~761℃;晚期角闪石为镁角闪石,结晶压力为128 MPa~167 MPa,对应的岩体侵位深度为4.2km~5.5km,结晶温度为632℃~692℃。黑云母为镁质黑云母,镁质率为0.45~0.70,说明岩体属于深源系列,其成分特征指示岩体具有壳幔混源的成因特点,结晶温度为650℃~700℃。结合岩体的稀土元素、同位素地球化学数据分析表明:来自与上地幔的岩浆上侵至中下地壳(约14.7km),并发生同化混染作用和结晶分异演化,随后快速的上侵至近地表(约4.8km),最后冷凝固结为天鹅抱蛋山闪长岩。
The Tian′ebaodanshan quartz diorite is closely related with the Tianmashan gold deposit.The forming conditions of the rock body and its geological significance with the petrographic and mineralogical characteristics of the Tian′ebaodanshan quartz diorite are studied.Plagioclases in the rocks consist of oligoclase with An ranging from 23 to 30and andesine with An ranging from 31 to 38.Normal oscillatory zoning indicates that the rock body experienced rapid uplift in the process of formation.The early stage hornblendes are edenite formed at pressure of 301 MPa~504 MPa,at depth of 9.9km~16.6km and at temperature of 721 ℃~761 ℃.The late stage hornblendes are magnesiohornblende formed at pressure of 128 MPa~167 MPa,at depth of 4.2km~5.5km and at temperature of 650 ℃ ~700 ℃.Biotites in the rocks belong to Mg-biotites with the ratios of Mg/(Mg+Fe~(2+)+Mn)ranging from 0.45 to 0.70,indicating that the rocks belong to deep-source series.Analysis of chemical composition of the biotites reveals that it is resulted from a mixed source of mantle and crust and the crystallization temperature ranges from 650℃to 700 ℃.Comprehensive analysis of the geochemical data of isotope and REE and mineralogical characteristics indicates that magma emplaced from upper mantle to middle-lower crust(about14.7km)and accompanied by fractionation crystallization and assimilation.Subsequently,the magma rapidly emplaced to the shallow part of earth′s surface(about 4.8km)and eventually formed the Tian′ebaodanshan quartz diorite.
The Tian′ebaodanshan quartz diorite is closely related with the Tianmashan gold deposit.The forming conditions of the rock body and its geological significance with the petrographic and mineralogical characteristics of the Tian′ebaodanshan quartz diorite are studied.Plagioclases in the rocks consist of oligoclase with An ranging from 23 to 30and andesine with An ranging from 31 to 38.Normal oscillatory zoning indicates that the rock body experienced rapid uplift in the process of formation.The early stage hornblendes are edenite formed at pressure of 301 MPa~504 MPa,at depth of 9.9km~16.6km and at temperature of 721 ℃~761 ℃.The late stage hornblendes are magnesiohornblende formed at pressure of 128 MPa~167 MPa,at depth of 4.2km~5.5km and at temperature of 650 ℃ ~700 ℃.Biotites in the rocks belong to Mg-biotites with the ratios of Mg/(Mg+Fe~(2+)+Mn)ranging from 0.45 to 0.70,indicating that the rocks belong to deep-source series.Analysis of chemical composition of the biotites reveals that it is resulted from a mixed source of mantle and crust and the crystallization temperature ranges from 650℃to 700 ℃.Comprehensive analysis of the geochemical data of isotope and REE and mineralogical characteristics indicates that magma emplaced from upper mantle to middle-lower crust(about14.7km)and accompanied by fractionation crystallization and assimilation.Subsequently,the magma rapidly emplaced to the shallow part of earth′s surface(about 4.8km)and eventually formed the Tian′ebaodanshan quartz diorite.
引文
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[14]吕志成,段国正,董光华.大兴安岭中南段燕山期三类不同成矿花岗岩中黑云母的的化学成分特征及其成岩成矿意义[J].矿物学报,2003,23(2):177-184.
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[19]Henry D J,Guidotti C V,Thomoson J A.The Tisaturation surface for low-to-medium pressure metapelitic biotites:Implications for geothermonmetry and Ti-substitution mechanisms[J].Am Mineral,2005,90:316-328.
[20]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.
[21]王听渡,张秀棋,徐永生.内蒙古昭盟地区中生代火山岩中斜长石环带特征及其地质意义[J].地质科学,1985,(2):161-168.
[2]徐涛.铜陵天马山硫金矿床成矿地质特征及深部找矿方向[J].现代矿业,2012,(517):35-38.
[3]李学明,李彬贤,张巽,等.马山金矿的同位素组成[J].中国科学技术大学学报,1987,17(3):408-412.
[4]田世洪,侯增谦,杨竹森,等.安徽铜陵马山金硫矿床稀土元素和稳定同位素地球化学研究[J].地质学报,2007,81(7):929-937.
[5]周曙光.天鹅抱蛋山硫金矿床地质特征及其成因探讨[J].矿业快报,2003,(9):13-17.
[6]Pan Y M,Dong P.The lower changjiang(Yangzi/Yangtze River)metallogenic belt,east central China:intrusion-and wall rock-hosted CuFe-Au,Mo,Zn,Pb,Ag deposits[J].Ore Geology Review,1999,15:177-242.
[7]郑巧荣.由电子探针分析值计算Fe3+和Fe2+[J].矿物学报,1983,(1):55-62.
[8]叶慧文.角闪石族矿物探针分析值中Fe3+和Fe2+的配分研究[J].见:张贻侠,卢兆良,阎鸿铨,徐学纯(主编).长春地质学院地质研究所文集[A].北京:地震出版社,1992,63-74.
[9]IMA-CNMMN角闪石专业委员会全体成员.角闪石命名法-国际矿物学协会新矿物及矿物命名委员会角闪石专业委员会的报告[J].岩石矿物学杂志,2001,20(1):84-99.
[10]张爱萍,杜杨松,曹毅,等.安徽铜陵凤凰山花岗闪长岩岩石学和矿物学特征及其地质意义[J].矿物岩石,2012,32(2):31-37.
[11]Foster M D.Interpretation of composition of trioctahedral micas[J].U S Geol Surv Prof Paper,1960,354B:1-49.
[12]周瑜若,任进.长江中下游中生代花岗岩[M].北京:地质出版社,1994:47,71-73.
[13]蒋国豪,胡瑞忠,谢桂青,等.大吉山花岗岩体黑云母地球化学特征及其成岩成矿意义[J].矿物岩石,2005,25(5):58-61.
[14]吕志成,段国正,董光华.大兴安岭中南段燕山期三类不同成矿花岗岩中黑云母的的化学成分特征及其成岩成矿意义[J].矿物学报,2003,23(2):177-184.
[15]周作侠.湖北丰山洞岩体成因探讨[J].岩石学报,1986,2(1):59-70.
[16]Johnson M C,Rutherford M J.Experimental calibration of the aluminum-in-hornblende geobarometer with application to Long Valley Caldera(California)volcaic rocks[J].Geology,1989,17(11):837-841.
[17]Schmidt M W.Amphibole composition in tonalite as a function of pressure,an experimental calibration of the Al-in-hornblende barometer.Contrib[J].Mineral Petrol,1992,110:304-310.
[18]Blundy J D,Holland T J B.Calcic amphibole equilibria and a new amphibole-plagioclase geothermometer[J].Contribution to Mineralogy and Petrology,1990,104:208-224.
[19]Henry D J,Guidotti C V,Thomoson J A.The Tisaturation surface for low-to-medium pressure metapelitic biotites:Implications for geothermonmetry and Ti-substitution mechanisms[J].Am Mineral,2005,90:316-328.
[20]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.
[21]王听渡,张秀棋,徐永生.内蒙古昭盟地区中生代火山岩中斜长石环带特征及其地质意义[J].地质科学,1985,(2):161-168.
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