海南石碌地区早三叠世闪长玢岩脉U-Pb年代学及构造意义  

Early Triassic Diorite-Porphyrite Dikes from the Shilu Area, Hainan Island: Zircon U-Pb Age and Tectonic Implication

作　　者：李艳军[1] 魏俊浩[1] 伍刚[1] 谭俊[1] 石文杰[1] 赵少卿[1] 王永辉[2] 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]海南矿业股份有限公司,海南昌江572700

出　　处：《地球科学（中国地质大学学报）》2013年第2期241-252,共12页Earth Science-Journal of China University of Geosciences

基　　金：全国危机矿山"桂东粤西地区铅锌金等矿床成矿规律总结研究"项目(No.20089946);中国地质大学(武汉)中央高校基本科研业务费专项基金(Nos.CUG110832;CUG120702);国家自然科学基金项目(No.41202054);中国地质大学地质过程与矿产资源国家重点实验室基金

摘　　要：石碌铁矿床位于海南岛五指山褶皱带西段.矿区内外发育以闪长玢岩脉为主的中基性脉岩.LA-ICP-MS锆石U-Pb定年厘定闪长玢岩脉年龄为248±1Ma(MSWD=0.4),为早三叠世岩浆活动的产物,与同时代的富碱侵入岩体构成"双峰式"侵入岩.闪长玢岩脉为钾玄质系列,低SiO2(49.18%～55.25%)、高Al2O3(14.36%～16.75%)、FeOt(5.98%～10.07%)和MgO(3.80%～5.43%),富集LILE和LREE,亏损HFSE.Nb/Ta、Zr/Hf和La/Nb比值分别为15.33～17.80、36.00～45.23和2.59～8.62;Pb同位素组成(206Pb/204Pb)t=18.087～18.483,(207Pb/204Pb)t=15.473～15.587,(208Pb/204Pb)t=38.272～38.817.LREE/HFSE和LILE/HFSE比值及Pb同位素组成显示为富集地幔来源,但混染有少量的地壳物质.HFSE判别图解指示闪长玢岩脉形成于大陆边缘弧伸展背景,与晚二叠世印支板块NE向向华南地块俯冲造成的大陆边缘弧局部伸展有关.The Shilu iron deposit is located in western section of the Wuzhishan Fold Belt, Hainan island. In this region, numerous intermediate-basic dikes dominated by diorite-porphyrite occurred. The dating of zircon from diorite-porphyrite dikes determined by LA-ICP-MS yields age of 248±1 Ma （MSWD=0. 4）, maybe himodal intrusion with contemporary alkali-rich granites. Diorite-porphyrite dikes are dominated by shoshonitic rocks, which have SiO2 varying from 49. 18% to 55.25%, Al2O3 from 14. 36% to 16.75%, FeO, from 5. 98% to 10. 07% and MgO ranging from 3. 80% to 5.43%. These dikes are enriched in large ion lithophile elements （LILE） and low rare earth elements （LREE） but depleted in high field strength element （HFSE）. The Nb/Ta values of diorite-porphyrite vary from 15. 33 to 17. 80, Zr/Hf and La/Nb from 36. 00 to 45. 23 and 2.59 to 8. 62, respectively. Two samples have （206 pb/204 Pb）, = 18. 087 - 18. 483, （207 pb/204 Pb）t = 15. 473 - 15. 589 and （208 pb/204 Pb）, = 38. 272-38. 817, similar to the data of contemporary alkali-rich granites. Geochemical and Pb isotopic compositions indicate that these dikes are possibly derived from enriched mantle and slightly contaminated with crust. Hf/3-Th-Ta and Zr-Zr/Y discriminant diagrams imply these diorite-porphyrite dikes intruded in a local nextensional tectonic setting in continental arc, caused by the Indian plate northeastern subduction to the South China Block.

关 键 词：闪长玢岩脉 早三叠世 大陆边缘弧 石碌铁矿床 地质年代学 海南岛 

分 类 号：P597[天文地球—地球化学]