Zircon SHRIMP U–Pb geochronology of potassic felsic intrusions in western Yunnan, SW China: Constraints on the relationship of magmatism to the Jinsha suture
Zircon SHRIMP U–Pb geochronology of potassic felsic intrusions in western Yunnan, SW China: Constraints on the relationship of magmatism to the Jinsha suture
复制标题
DOI：
10.1016/j.gr.2011.11.016
复制
发表时间：
2012-09
影响因子：
6.1
通讯作者：
Yongjun Lu;R. Kerrich;Peter A. Cawood;T. McCuaig;C. Hart;Zhengyuan Li;Z. Hou;L. Bagas
中科院分区：
文献类型：
--
作者：
Yongjun Lu;R. Kerrich;Peter A. Cawood;T. McCuaig;C. Hart;Zhengyuan Li;Z. Hou;L. Bagas
滇西哀牢山-红河剪切带钾质长英质侵入体与钾质镁铁质岩浆活动同时空、同走滑位移沿着的关系一直存在很大争议。本文报道了剪切带以东150 km和以西50 km的19个钾质长英质侵入体的22个新的SHRIMP锆石U-Pb年龄。结果表明，滇西长英质岩体的侵位时间为36.9±0.3Ma ~ 32.5±0.3Ma。这一年龄范围明显短于15个岩体K-Ar和Ar-Ar法测年的38 ~ 23 Ma，表明后者为重置或冷却年龄。钾质长英质侵入体与同一地区的钾质镁铁质火山岩（36.6Ma-33.4Ma）是同时代的，支持了两个端员之间可能的成因联系。定年的侵入体发生在哀牢山-红河剪切带上200 km宽的区域内，因此它们不太可能与剪切作用有关。滇西钾质镁铁质岩浆作用可能与印支-亚洲大陆碰撞后，始新世-早渐新世沿沿着中生代金沙缝合带俯冲改造的地幔岩石圈的拆沉和熔融有关;钾质长英质岩浆是与镁铁质液体混合的地壳熔体。拆离作用反过来又促进了哀牢山-红河剪切带的形成，并使剪切带的形成局限于约1000 m。32 Ma大陆挤压期。
The relationship between potassic felsic intrusions, cospatial and cotemporal with potassic mafic magmatism, and strike–slip displacement along the Ailao Shan-Red River shear zone in western Yunnan, SW China has been highly controversial. We report 22 new SHRIMP zircon U–Pb ages from 19 potassic felsic intrusions located as far as 150km east and 50km west of the shear zone to constrain temporal relationships. The results show that the felsic intrusions in western Yunnan were emplaced between 36.9±0.3Ma and 32.5±0.3Ma. This age range is significantly shorter than previous dating of 38Ma to 23Ma using K–Ar and Ar–Ar methods from 15 intrusions, indicating that the latter are reset or cooling ages. Potassic felsic intrusions are coeval with potassic mafic volcanic rocks (36.6Ma to 33.4Ma) in the same area, supporting a possible genetic link between the two end members. The dated intrusions occur over a 200km wide zone across the Ailao Shan-Red River shear zone; therefore they are unlikely genetically related to shearing. Rather, potassic mafic magmatism in western Yunnan may be related to delamination and melting of previously subduction-modified mantle lithosphere along the Mesozoic Jinsha suture reactivated in the Eocene–Early Oligocene, following the India-Asia continental collision; potassic felsic magmas were crustal melts hybridized with mafic liquids. Delamination in turn facilitated and localized initiation of the Ailao Shan-Red River shear zone at ca. 32Ma during continental extrusion.