Early Triassic Diorite-Porphyrite Dikes from the Shilu Area, Hainan Island: Zircon U-Pb Age and Tectonic Implication
详细信息
- 责任者：Li Yanjun (Faculty of Earth Resources ; China University of Geosciences ; Wuhan 430074 ; China) ; Wei Junhao
- 刊名：Earth Science
- 出版年：2013
- 卷期：38(2)
- 关键词：闪长玢岩 ; diorite porphyry ; 铀—铅计时 ; U-Pb dating ; 海南 ; Hainan Province
- 页码：p.241-252
- 图表：illus., 4 tables, 47 refs.
- 分类号：0801
- issnNo：ISSN1000-2383
- isbnNo：CN42-1233/P
摘要
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 bimodal 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%, FeOt 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 (206Pb/204Pb)t=18.087-18.483, (207Pb/204Pb)t=15.473-15.589 and (208Pb/204Pb)t=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.
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