Mantle Source Components and Magmatic Evolution for the Comei Large Igneous Province:Evidence from the Early Cretaceous Niangzhong Mafic Magmatism in Tethyan Himalaya

• 作者: Yaying Wang Lingsen Zeng Kejun Hou Li'e Gao Qian Wang Linghao Zhao Jiahao Gao Guangxu Li
• 来源期刊: 地球科学学刊（英文版）
• 年，卷（期）: 2022,（1）
• 所属期刊栏目: Special Issue on Isotope Geochronology and Isotope Geochemistry
• 页码范围: 133-149
• 页数: 17页
• 语种: 英文

摘要

The Niangzhong diabase dikes, dated at 138.1 ± 0.4 Ma, are located within the outcrop area of the Comei large igneous province (LIP). These diabase samples can be divided into two groups:samples in Group 1 show varying MgO (1.50 wt.％-10.25 wt.％) and TiO2 (0.85 wt.％-4.63 wt.％) con-tents, and enriched initial isotope compositions (87Sr/86Sr(t)=0.7056-0.7112,εNd(t)=-0.3-+3.8), with OIB-like REEs and trace elements patterns, resulting from low degree melting of garnet-bearing lher-zolite mantle sources;in contrast, samples in Group 2 show limited MgO (4.14 wt.％-7.75 wt.％) and TiO2 (0.98 wt.％-1.69 wt.％) contents, and depleted initial isotope compositions (87Sr/86Sr(t)=0.7075-0.7112,εNd(t)=+5.5-+6.2), with N-MORB-like REEs and trace elements patterns, resulting from rela-tively high degree melting of spinel-bearing lherzolite mantle source. Combined with the published rep-resentative data about Comei LIP, we summarize that the source components for Comei LIP products include OIB end-member, enriched OIB end-member, and N-MORB end-member, respectively. Melts modeling suggests that magmas in the Comei LIP evolve in a relatively high oxygen fugacity condition, which influenced their fractionation sequences and led to systematic changes of TiO2 contents, Ti/Y and Ti/Ti* ratios. From the spatial and temporal distribution of above three end-member samples, deep process of Kerguelen plume during the Comei LIP formation can be interpreted as the interaction among the Kerguelen plume, the overlying lithospheric mantle, and the upwelling asthenosphere. The magmatism of Comei LIP began at～140 Ma and then lasted and peaked at～132 Ma with the progres-sively lithospheric thinning of eastern Gondwana upon the impact of Kerguelen plume.