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| 滇西三江地区临沧花岗岩的岩石成因:地球化学、锆石U-Pb年代学及Hf同位素约束 | |
| 引用本文： | 孔会磊,董国臣,莫宣学,赵志丹,朱弟成,王硕,李荣,王乔林.滇西三江地区临沧花岗岩的岩石成因:地球化学、锆石U-Pb年代学及Hf同位素约束[J].岩石学报,2012,28(5):1438-1452. |
| 作者姓名： | 孔会磊 董国臣 莫宣学 赵志丹 朱弟成 王硕 李荣 王乔林 |
| 作者单位： | 1. 中国地质大学,北京100083;中国地质调查局西安地质调查中心,西安710054 2. 中国地质大学,北京100083;中国地质大学地质过程与矿产资源国家重点实验室,北京100083 3. 中国地质大学,北京,100083 |
| 基金项目： | 本文受国家重点基础研究发展规划项目(2009CB421002)、111计划项目(B07011)和中国地质调查局综合研究项目(1212010610104)联合资助. |
| 摘 要： | 位于滇西三江地区南澜沧江带的临沧花岗岩,其岩石类型主要为黑云母二长花岗岩,研究结果表明,该花岗岩的SiO2含量为66.84%～73.99%,平均为69.72%,K2O/Na2O值高,为1.42～30.1,平均为8.66,Al2O3含量为12.94%～15.23%,平均为14.44%,铝饱和指数A/CNK为1.06～8.59,平均为2.61,大部分大于1.1,为高钾钙碱性过铝-强过铝花岗岩。岩石总体上富集大离子亲石元素和Pb,明显亏损高场强元素。稀土总量198.2×10-6～359.2×10-6,平均为252.5×10-6,具有明显的轻稀土富集,重稀土亏损的特征,(La/Yb)N为7.87～17.62,平均11.19,δEu为0.34～0.57,平均0.48,球粒陨石标准化配分模式显示明显的负Eu异常。两件样品的锆石U-Pb年龄分别为219.19±0.99Ma和219.69±0.67Ma,属晚三叠世。SiO2-P2O5、SiO2-Zr判别图、K2O-Na2O判别图、ACF图解等花岗岩成因类型判别图指示临沧花岗岩为S型花岗岩,其物质来源为贫粘土的砂屑岩。微量元素Rb-Y+Nd判别图中,临沧花岗岩体投影点全部落入后碰撞花岗岩区。在Sr-Yb判别图中,投影点大部分落入低Sr高Yb型花岗岩区,与我国东南沿海花岗岩特征一致,应形成于挤压向伸展转换的后碰撞阶段。锆石Hf同位素组成比较均一,εHf(t)均为负值(集中于-14～-11之间),Hf地壳模式年龄集中于1.95～2.15Ga,推断其为古老地壳部分熔融的产物。结合锆石定年结果及岩体产出的区域地质背景,我们认为临沧花岗岩形成于缅泰马陆块与思茅地块大陆碰撞造山过程的后碰撞阶段,应形成于晚三叠世。 |
| 关 键 词： | 锆石U-Pb年龄 地球化学 Hf同位素 临沧花岗岩 滇西三江 |
| 收稿时间： | 2011/4/11 0:00:00 |
| 修稿时间： | 2011/7/10 0:00:00 |
Petrogenesis of Lincang granites in Sanjiang area of western Yunnan Province: Constraints from geochemistry, zircon U-Pb geochronology and Hf isotope |
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| KONG HuiLei,DONG GuoChen,MO XuanXue,ZHAO ZhiDan,ZHU DiCheng,WANG Shuo,LI Rong and WANG QiaoLin.Petrogenesis of Lincang granites in Sanjiang area of western Yunnan Province: Constraints from geochemistry, zircon U-Pb geochronology and Hf isotope[J].Acta Petrologica Sinica,2012,28(5):1438-1452. | |
| Authors: | KONG HuiLei DONG GuoChen MO XuanXue ZHAO ZhiDan ZHU DiCheng WANG Shuo LI Rong and WANG QiaoLin |
| Institution: | China University of Geosciences, Beijing 100083, China;Xi'an Center of China Geological Survey, Xi'an 710054, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China;China University of Geosciences, Beijing 100083, China |
| Abstract: | The Lincang granites in southern Lancangjiang zone of Sanjiang area,located in the west of Yunnan Province,are mainly composed of biotitic monzogranites.The SiO2 and Al2O3 of the granites range 66.84% ～ 73.99% and 12.94% ～ 15.23%,averagely 69.72% and 14.44% respectively.The K2O/Na2O ratio is high,ranging 1.42 ～ 30.1,with average of 8.66.A/CNK varies from 1.06 to 8.59,averagely 2.61,and mostly > 1.1.So Lincang granites are high-K calc-alkaline and peraluminous to strongly peraluminous series.Lincang granites are also enriched in LILEs and Pb,but strongly depleted in HFSEs.The REE content is between 198.2 × 10-6 and 359.2 × 10-6(average 252.5 × 10-6),with(La/Yb) N ratios of 7.87 ～ 17.62(average 11.19) and δEu of 0.34 ～ 0.57(average 0.48).The intrusion is remarkably characterized by enriched LREE and depleted HREE.The chondrite-normalized REE patterns show strong negative Eu anomalies.The zircon U-Pb ages of the two samples are 219.19 ± 0.99Ma and 219.69 ± 0.67Ma,belonging to Late Triassic.The SiO2-P2O5,SiO2-Zr,K2O-Na2O relationship and ACF plot indicate that the Lincang granites are S type granites,which mainly derive from clay-poor psammite.Lincang granites can be dropped into the group of post-collisional granites in the Rb-Y + Nd discrimination diagram.In addition,Lincang granites have the features of low-Sr and high-Yb in the Sr-Yb discrimination diagram,which is in accordance with the granites in southeastern China.Lincang granites have homogeneous zircon Hf isotopic composition.Their zircons have negative εHf(t) values(-14 ～-11) and old Hf isotope crust model ages(1.95 ～ 2.15Ga),suggesting that Lincang granites were formed by partial melting of old crust.Therefore,we consider that Lincang granites were formed in post-collisional stage between the Burma-Thai-Malaysia and Simao block in the Late Triassic. |
| Keywords: | Zircon U-Pb geochronology Geochemistry Hf isotope Lincang granites Sanjiang area of western Yunnan |
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