Middle-Late Ordovician arc-type plutonism in the NW Chinese Tianshan: Implication for the accretion of the Kazakhstan continent in Central Asia

详细信息	查看全文 | 推荐本文 |

• 作者：Bo Wang^a ; ^b ; ^{burh_cw@yahoo.com} ; Bor-ming Jahn^b ; ^c ; Liangshu Shu^a ; Kongsen Li^a ; Sun-lin Chung^c ; Dunyi Liu^d
• 关键词：Early Paleozoic arc ; SHRIMP U&ndash ; Pb dating ; Geochemistry ; Tianshan (Tien Shan) ; Kazakhstan ; Central Asian Orogenic Belt (CAOB)
• 刊名：Journal of Asian Earth Sciences
• 出版年：2012
• 期刊代码：40_13679120
• 类别：ear
• 出版时间：30 April, 2012
• 卷：49
• 期：Complete
• 页码：40-53
• 文件大小：4353 K

摘要

Kazakhstan is one of the largest continental assemblages within the Central Asian Orogenic Belt. It was formed by accretion and amalgamation of several continental fragments and island arcs during early Paleozoic. The Aktau - Wenquan domain is one important continental constituent within the Kazakhstan and is located in the northeast of the Kazakhstan. Late Ordovician arc-type magmatic rocks were recently recognized from the Wenquan Group, which is long known to be Paleoproterozoic. Our investigation in the southern Wenquan area (NW China) suggests that within the Wenquan Group, foliated magmatic rocks are largely different from the amphibolite in terms of petrographic texture, protolith age, geochemical composition and Sm-Nd model age. New SHRIMP zircon U-Pb ages were determined for two deformed diorites, one gabbro enclave and a monzodiorite dyke at 466 卤 4-447 卤 6 Ma, 462 卤 5 Ma and 450 卤 9 Ma, respectively. Zircons of the monzodiorite dyke contain inherited cores of 鈭?000 to 鈭?400 Ma. The new geochemical analyses and literature data show that the magmatic rocks are of subduction-related calc-alkaline affinity. The 蔚Nd(t) values range from 鈭?.0 to 0.8 and Nd model ages from 1.0 to 1.2 Ga, indicating variable involvement of Proterozoic crust in the generation of the Early Paleozoic magmatic rocks. Consequently, these rocks were mostly likely emplaced in a continental arc environment, probably in the northern margin of the Aktau - Wenquan continental domain. Regional comparison suggests that this arc magmatism could probably be linked with the Karamai and/or North Balkhash accretionary wedges, and resulted from subduction of the Junggar-Balkhash oceanic lithosphere during Middle to Late Ordovician. Subsequent continental - arc collision and continuing accretion during Middle - Late Paleozoic in north of the Kazakhstan overprinted the structure of Early Paleozoic active continental margin in the Aktau - Wenquan domain.