中甸岛弧红山地区两期中酸性侵入岩的年代学、地球化学特征及其成因  

Geochronology,geochemistry and petrogenesis of two periods of intermediate-acid intrusive rocks from Hongshan area in Zhongdian arc

作　　者：黄肖潇[1,2] 许继峰[1] 陈建林[1] 任江波[3] 

机构地区：[1]同位素地球化学国家重点实验室,中国科学院广州地球化学研究所,广州510640 [2]中国科学院研究生院,北京100039 [3]广州海洋地质调查局,广州510075

出　　处：《岩石学报》2012年第5期1493-1506,共14页Acta Petrologica Sinica

基　　金：国家973项目(2009CB421004);中科院知识创新项目(KZCX2-YW-Q04);国家自然科学基金项目(40872055;40930316;41073033);中国地质调查局项目(1212010818098)联合资助

摘　　要：青藏高原东部中甸岛弧红山地区发育有印支期和燕山晚期两期中酸性岩浆侵入活动,主要集中在～216Ma和～76Ma两个时期。印支期中酸性岩浆的侵入活动形成于甘孜-理塘洋西向俯冲背景下,与矽卡岩型铜多金属成矿作用密切相关。形成于印支期的红山石英闪长玢岩具有埃达克质岩的部分地球化学特征,如高Sr(平均为938×10-6)、低Y(平均为18.6×10-6)、Yb(平均为1.7×10-6)含量,轻重稀土分异明显((La/Yb)N平均为20.1),同时也有着较高的Mg#(平均为51)、Cr(平均为103×10-6)、Ni(平均为22×10-6)含量,指示印支期红山中酸性岩与普朗-雪鸡坪成矿岩体有着相似的地球化学特征,二者可能有着相似的物质源区和成岩模式。而形成于燕山晚期的红山花岗斑岩具有低Sr含量(平均为149×10-6)和更低的Y(平均为10.8×10-6)、Yb(平均为0.9×10-6)含量,轻重稀土强烈分异((La/Yb)N平均为56.0),明显区别于义敦岛弧弧后区的高贡-措莫隆A型花岗岩,前者很可能是红山中下地壳部分熔融的产物。结合中甸岛弧发育于燕山晚期的斑岩型矿床,我们认为该地区发育于燕山晚期的中酸性岩浆作用以及与之相联系的斑岩型矿床形成于造山后伸展环境下。Two periods of intermediate-acid magmatic activities occur in Hongshan area,Zhongdian arc,which were mainly emplaced at ～ 216Ma and ～ 76Ma,respectively.The 216Ma magmatism,which is associated with the porphyric Cu-Mo mineralization,was produced during the westward subduction of Ganzi-Litang ocean plate in Late Triassic.It is composed of quartz dioritic porphyrites,and shows some geochemical characteristics of an adakite,such as high Sr（938 × 10-6 in average）,but low Y（18.6 ×10-6 in average）,Yb（1.7 ×10-6 in average） contents,and strongly fractionation between LREE and HREE（（La/Yb） N = 20.1 in average）.Meanwhile,it has relatively high Mg#（51 in average）,Cr（103 × 10-6 in average） and Ni（22 × 10-6 in average） concentrations.These quartz dioritic porphyrites show geochemical characteristics same as or similar to those of the ore-bearing rocks in Pulang-Xuejiping,hinting that the both had a similar composition in source and/or were formed by a tectonic event.On the other hand,76Ma granitic porphyries in Hongshan area have low Sr（149 × 10-6 in average）,Y（10.8 × 10-6 in average） and Yb（0.9 × 10-6 in average） concentrations,and strongly fractionation between LREE and HREE（（La/Yb） N = 56.0 in average）,which is obviously different from the A-type granite of Gaogong-Cuomolong in Yidun island arc.It is likely the result of partial melting of the middle-lower crust of Hongshan area.Combined with other porphyric rocks and deposits in Zhongdian arc,the 76Ma intermediate-acid magmatism in Hongshan area,which is associated with porphyric mineralization,were generated in a post-orogenic extensional setting in Late Cretaceous.

关 键 词：斑岩矿床 地球化学 中酸性岩浆活动 红山 中甸岛弧 

分 类 号：P588.121[天文地球—岩石学] P588.122[天文地球—地质学]