甘孜-理塘结合带南段德工牛场铜多金属矿区斑岩体地球化学特征
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摘要
德工牛场铜多金属矿床是位于甘孜-理塘结合带南段的一处斑岩型矿床,矿区与成矿关系最为密切的斑岩体为花岗闪长斑岩。该岩体与甘孜-理塘洋演化以及与斑岩型矿床间的关系是值得深入研究的课题。对矿区花岗闪长斑岩进行了地球化学研究,结果表明:花岗闪长斑岩具有高硅(w(SiO_2)66.35%~71.86%)、高碱(w(K_2O+Na_2O)3.63%~7.08%)、高钾(w(K_2O)3.11%~4.57%)和过铝质(A/CNK 0.96~1.49)等特征,里特曼组合指数σ为0.56~1.74;稀土元素总量偏少(w(ΣREE)111.56×10~(-6)~121.00×10~(-6)),轻重稀土元素分馏明显((La/Yb)_N6.63~9.51);相对富集Rb、K、La等大离子亲石元素(LILE)及高场强元素(HFSE)Th、U,相对亏损Nb、Ta、P、Ti等高场强元素及部分大离子亲石元素(如Ba、Sr);Fe_2O_3/FeO比值平均为1.11。综合地球化学特征表明,德工牛场花岗闪长斑岩为高钾钙碱性过铝质I型花岗岩,是典型的壳幔混源成因类型,具有岛弧花岗岩的特征;结合地质年龄资料(216Ma)与区域构造演化特征,判定其为印支末期甘孜-理塘洋向西侧中咱地块俯冲时在强烈的岩浆活动中形成,矿床的花岗闪长斑岩在成岩构造事件与成矿岩石特征方面与义敦岛弧内典型斑岩型矿床的斑岩具有高度的相似性。
The Degongniuchang Cu polymetallic deposit,located in southern section of Garzê-Litang suture zone,is characterized by porphyry deposit,where the ore-related porphyry is granodiorite porphyry.To study the relationship between the granodiorite porphyry with the Garzê-Litang oceanic evolution and porphyry deposits,this paper analyzes the geochemistry characteristics of granodiorite porphyry.The results show that Degongniuchang granodiorite porphyry is characterized by SiO_2-rich(with the content ranging from 66.35%to 71.86%),alkaline(with the content of K_2O+Na_2O 3.63%-7.08%),K-high(with the content of K_2O 3.11%-4.57%),peraluminous(with the ratio of A/CNK 0.96-1.49),and itsσvalues is 0.56-1.74.The results also indicate that the Degongniuchang granodiorite porphyry has normal total REE content(with the content of 111.56×10~(-6)-121.00×10~(-6))and high fractionation between light and heavy REE(with the ratio of(La/Yb)_N6.63-9.51),and enrichment in the large ionlithophile elements(LILE)(Rb,K,La)and high field strength elements(HFSE)(Th,U)as well as with marked negative Nb,Ta,P,Ti and some large ionlithophile elements Ba,Sr,and the average ratio of Fe_2O_3/FeO is 1.11.Th above characteristics suggest that the Degongniuchang granodiorite porphyry should belong to high-K clacalkaline peraluminous I-type granite.The source of the granodiorite porphyry has continental crust andmantle-derived features,with features of volcanic arc environment.Combined with geological age data(216Ma)and regional tectonic evolution,the granodiorite porphyry in the Degongniuchang most likely formed in the island arc environment resulted from the westward subduction of the Garzê-Litang oceanic plate beneath the Zhongza block in Indosinian.The granodiorite porphyry has a high degree of similarity with the typical porphyry deposits located in Yidun island arc in the diagenetic tectonic events and metallogenic rocks.
The Degongniuchang Cu polymetallic deposit,located in southern section of Garzê-Litang suture zone,is characterized by porphyry deposit,where the ore-related porphyry is granodiorite porphyry.To study the relationship between the granodiorite porphyry with the Garzê-Litang oceanic evolution and porphyry deposits,this paper analyzes the geochemistry characteristics of granodiorite porphyry.The results show that Degongniuchang granodiorite porphyry is characterized by SiO_2-rich(with the content ranging from 66.35%to 71.86%),alkaline(with the content of K_2O+Na_2O 3.63%-7.08%),K-high(with the content of K_2O 3.11%-4.57%),peraluminous(with the ratio of A/CNK 0.96-1.49),and itsσvalues is 0.56-1.74.The results also indicate that the Degongniuchang granodiorite porphyry has normal total REE content(with the content of 111.56×10~(-6)-121.00×10~(-6))and high fractionation between light and heavy REE(with the ratio of(La/Yb)_N6.63-9.51),and enrichment in the large ionlithophile elements(LILE)(Rb,K,La)and high field strength elements(HFSE)(Th,U)as well as with marked negative Nb,Ta,P,Ti and some large ionlithophile elements Ba,Sr,and the average ratio of Fe_2O_3/FeO is 1.11.Th above characteristics suggest that the Degongniuchang granodiorite porphyry should belong to high-K clacalkaline peraluminous I-type granite.The source of the granodiorite porphyry has continental crust andmantle-derived features,with features of volcanic arc environment.Combined with geological age data(216Ma)and regional tectonic evolution,the granodiorite porphyry in the Degongniuchang most likely formed in the island arc environment resulted from the westward subduction of the Garzê-Litang oceanic plate beneath the Zhongza block in Indosinian.The granodiorite porphyry has a high degree of similarity with the typical porphyry deposits located in Yidun island arc in the diagenetic tectonic events and metallogenic rocks.
引文
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[2]莫宣学,潘桂棠.从特提斯到青藏高原形成:构造-岩浆事件的约束[J].地学前缘,2006,13(6):43-51.
[3]李文昌.“西南三江”古特提斯构造演化研究新进展和新问题[C]∥沈爱民.新观点新学说学术沙龙文集55:板块汇聚、地幔柱对云南区域成矿作用的重大影响.昆明:中国科学技术出版社,2011.
[4]邓军,葛良胜,杨立强.构造动力体制与复合造山作用:兼论三江复合造山带时空演化[J].岩石学报,2013,29(4):1099-1114.
[5]李文昌,余海军,尹光候,等.西南“三江”格咱岛弧斑岩成矿系统[J].岩石学报,2013,29(4):1129-1144.
[6]侯增谦,潘桂棠,王安建,等.青藏高原碰撞造山带:Ⅱ.晚碰撞转换成矿作用[J].矿床地质,2006,25(5):521-543.
[7]侯增谦,曲晓明,杨竹森,等.青藏高原碰撞造山带:Ⅲ.后碰撞伸展成矿作用[J].矿床地质,2006,25(6):629-651.
[8]侯增谦,杨竹森,徐文艺,等.青藏高原碰撞造山带:I.主碰撞造山成矿作用[J].矿床地质,2006,25(4):337-358.
[9]邓军,王长明,李文昌,等.三江特提斯复合造山与成矿作用研究态势及启示[J].地学前缘,2014,21(1):52-64.
[10]邓军,杨立强,王长明.三江特提斯复合造山与成矿作用研究进展[J].岩石学报,2011,27(9):2501-2509.
[11]Peng T,Zhao G,Fan W,et al.Late Triassic granitic magmatism in the Eastern Qiangtang,Eastern Tibetan Plateau:Geochronology,petrogenesis and implications for the tectonic evolution of the Paleo-Tethys[J].Gondwana Research,2015,27(4):1494-1508.
[12] Lehmann B,Zhao X,Zhou M,et al.Mid-Silurian back-arc spreading at the northeastern margin of Gondwana:The Dapingzhang dacite-hosted massive sulfide deposit,Lancangjiang zone,southwestern Yunnan,China[J].Gondwana Research,2013,24(2):648-663.
[13]Fan J,Li C,Xie C,et al.Remnants of late Permian-Middle Triassic ocean islands in northern Tibet:Implications for the latestage evolution of the Paleo-Tethys Ocean[J].Gondwana Research,2017,44(2):7-21.
[14]四川省地质矿产开发局区域地质调查队.德工牛场斑岩型铜矿普查地质报告[R].成都:四川省地质矿产开发局区域地质调查队,2013.
[15]Hou Z Q.Tectono-magmatic evolution of the Yidun island-arc and geodynamic setting of kuroko-type sulfide deposits in Sanjiang Region,China[J].Resource Geology,1993,17:336-350.
[16]侯增谦,候立纬,叶庆同,等.三江地区义敦岛弧构造-岩浆演化与火山成因块状硫化物矿床[M].北京:地震出版社,1995.
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[18]李兴振,刘文均,王义昭,等.西南三江地区特提斯构造演化与成矿:总论[M].北京:地质出版社,1999.
[19]李兴振,江新胜,孙志明,等.西南三江地区碰撞造山过程[M].北京:地质出版社,2002.
[20]潘桂棠,徐强,侯增谦,等.西南“三江”多岛弧造山过程、成矿系统与资源评价[M].北京:地质出版社,2003.
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[23]莫宣学,邓晋福,董方浏,等,西南三江造山带火山岩-构造组合及其意义[J].高校地质学报,2001,7(2):121-138.
[24]杨海军,肖龙,吴涛,等.义敦岛弧带稻城贡巴纳过铝质花岗岩成因及构造意义[J].地质科技情报,2013,32(4):55-63.
[25]邓军,王庆飞,李龚健.复合造山和复合成矿系统:三江特提斯例析[J].岩石学报,2016,32(8):2225-2247.
[26]邓军,侯增谦,莫宣学,等.三江特提斯复合造山与成矿作用[J].矿床地质,2010,29(1):37-42.
[27]侯增谦,杨岳清,曲晓明,等.三江地区义敦岛弧造山带演化和成矿系统[J].地质学报,2004,78(1):109-120.
[28]李文昌,潘桂棠,侯增谦,等.西南“三江”多岛弧盆-碰撞造山成矿理论与勘查技术[M].北京:地质出版社,2010.
[29]邹光富,毛英,毛琼,等.西南三江地区大地构造演化与成矿作用[J].矿物岩石,2017,37(1):15-29.
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