Origin and Its Geological Significance of Late Carboniferous-Middle Permian Intermediate-acid Small Plutons in the Southeastern Awulale Area of West Tianshan, China(PDF)
《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]
- Issue:
- 2017年第02期
- Page:
- 175-193
- Research Field:
- 基础地质与矿产地质
- Publishing date:
Info
- Title:
- Origin and Its Geological Significance of Late Carboniferous-Middle Permian Intermediate-acid Small Plutons in the Southeastern Awulale Area of West Tianshan, China
- Author(s):
- HUANG Dong; ZHANG Cheng-li; MA Zhong-ping; HE Xian-ying; GAO Xiao-feng; WEI Qiang; YANG Rong; SUN Ji-ming; LI Ping
- 1. State Key Laboratory of Continental Dynamics, Northwest University, Xi’an 710069, Shaanxi, China;2. Xi’an Center of Geological Survey, China Geological Survey, Xi’an 710054, Shaanxi, China;3. Zhundong Oil Production Plant, Xinjiang Oilfield Company, PetroChina, Fukang 831511, Xinjiang, China
- Keywords:
- Intermediate-acid small plutons; zircon U-Pb age; geochemistry; Hf-isotope; origin; post-collision; West Tianshan
- PACS:
- P597+.3；P595
- DOI:
- -
- Abstract:
- Aikendaban granite and 2752 Gaodi dioritic porphyrite in the southeastern Awulale area of West Tianshan intrude into Carboniferous volcanicsedimentary sequences, showing undeformed uniform massive structures and porphyric/porphyriclike textures. Geochemically, they are enriched in large ion lithophile elements (Rb, Th, U, K, Pb, etc.), poor in high field strength elements (Zr, Hf, etc.), depleted in Nb, Ta, P, Ti, Sr, etc., Eu anomalies are weakmedium negative, displaying the feature similar to those of crust-derived magmatism in island arc. The zircons from Aikendaban granite and 2752 Gaodi dioritic porphyrite have positive εHf(t) and Neoproterozoic continental crust model age, suggesting that they result from the partial melting of Neoproterozoic continental crust materials; however, individual zircons have higher εHf(t),indicating the involvement of mantle-derived magmatic materials during the formation of granitic pluton. LA-ICP-MS zircon U-Pb ages of Aikendaban granite and 2752 Gaodi dioritic porphyrite are 282 Ma and 307 Ma, respectively; the ages correspond to the forming period of regional small plutons and the late period of large-scale crust-mantle granitic magmatism in West Tianshan, suggesting a small-scale intermediate-acid magmatism with the weakening of large-scale granitic magmatism from Late Carboniferous to Middle Permian. Based on the comprehensive analysis of Late Carboniferous-Middle Permian magmatism, the occurrence of these small plutons indicates an intermediate-acid magmatism, implying a decreasing of large-scale magmatism in the transitional stage from post-collision to intra-continental extension, and indicating an important turning point of the deep dynamical background and the tectonic environment in West Tianshan.
Last Update: 2017-03-31