Multiple Granitic Magma Events in Sanjiang Complex Belt, Yunnan Province: Implications for Tectonic Evolution
详细信息
- 责任者：Wang Fang (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Liu Fulai
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(6)
- 关键词：花岗岩类 ; granitoid ; 云南 ; Yunnan Province
- 页码：p.2141-2160
- 图表：illus., 10 tables, 79 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Sanjiang area is considered as the margin between Indian and Eurasian plates,recording multiple magmatic and metamorphic events. Eight granitoid rocks were collected from Diancang Shan and Gaoligong Shan complex for in situ zircon U-Pbdating and whole-rock geochemistry analysis. Based on geochronology results,six episodes of magmatism were recognized: Mid- Cambrian ( 501.2 ± 5. 0Ma) ,Late 0rdovician (456 ±2. 1Ma) ,Late Permian to Early Triassic (251 ～246Ma) ,Early Paleocene ( 55 ± 0. 62Ma) and Late Eocene (38 ± 0. 52Ma ) . Abundant Paleoproterozoic and Mid-Neoproterozoic inherited zirconswere also indentified. Geochemistry results show that SiO2 ,Al203 ,Na20 and K20 contents range form 60.41% to 77.41% ,11. 57% to 17. 54% ,2. 05% to4. 16% and2. 09%～6.31% ,respectively. Early Triassic granitoid rocks are characterized by peraluminous with A/CNK≥1,predominantly,while others are characterized by metaluminous with A/CNK ≥1. They show obvious fractionation of REE,negative Eu anomaly and ( La/Yb) N range from 5.22 to 19. 56. Five of them have 143 Nd/144 Nd ratios of 0. 51195 to 0. 51255, ε Nd ( t) values of 0 to - 11. 11 and Nd model ages ( t DM ) of 1071Ma to 1969Ma. The presences of two older samples suggest Mid- Cambrian and Late 0rdovician magmatism. The closure of Paleo-Tethys was responsible for Late Permian to Early Triassic magmatism. The Gaoligong Early Cretaceous granitoid rocks are the magmatic expression of crustal thickening. Cenozoic granitoid rocks are related to subduction-collision between the Indian and Eurasian plates. Inherited zircon yield major age clusters at 1100～800Ma,indicating Neoproterozoic magmatic event. A few Paleo-Midproterozoic zircons imply the existence of older basement rocks. Nd model ages also support that the Paleoproterozoic and Mid-Neoproterozoic occurred in this area.