长安大学李永军团队近日研究了柴达木北部东部闪长岩的岩石成因：对古特提斯洋构造演化的启示。相关论文于2025年6月18日发表在《地球化学学报》杂志上。

柴达木北部（NQ）的许多印支期火成岩为古特提斯洋的构造演化提供了至关重要的见解。研究组对北部东部闪长岩的岩石学、矿物学、地球化学、锆石U-Pb年代学和Hf同位素组成进行了全面研究。锆石U-Pb定年结果表明，闪长岩形成于中三叠世（244-240 Ma）。岩石表现出高钾钙碱性特征，SiO₂含量可变（55.25-65.39 wt%），K₂O + Na₂O（4.81-6.94重量%）含量升高。它们显示出LILE（Rb、Ba、K）的富集和HFSE（Nb、Ta、Ti）的贫化，并伴有轻微的负Eu异常（Eu/Eu* = 0.89–0.97）。锆石ε_Hf（t）值（-20.93至 + 5.60）和T_DM2年龄（0.85-1.72 Ga）表明了混合来源。 

岩相学和矿物学分析表明，斜长石斑晶表现出不平衡结构（包括反向分带），主要由安山岩和拉氏闪长岩组成，含少量低长石。斜辉石都是辉石，结晶温度很高（1111-1151°C）。这些特征，特别是斜长石的反向分带，支持了一种岩石成因模型，该模型涉及地幔源岩浆底侵，导致古代下地壳熔融，随后底侵玄武岩浆与地壳源长英质岩浆混合。该研究结果表明，宗武隆古特提斯洋俯冲过程中形成于弧后伸展环境中。

附：英文原文

Title: Petrogenesis of the dioritic rocks in the eastern North Qaidam: Implications for the tectonic evolution of the Paleo-Tethys Ocean

Author: Wang, Panlong, Li, Yongjun, Zhuang, Yujun, Gu, Pingyang, Shi, Chao, Yan, Jiaxin, Yang, Gaoxue, Li, Wei, Li, Hai, Zhang, Jianye, Fu, Hao

Issue&Volume: 2025-06-18

Abstract: Numerous Indosinian igneous rocks in the North Qaidam (NQ) provide crucial insights into the tectonic evolution of the Paleo-Tethys Ocean. This paper presents a comprehensive study of the petrography, mineralogy, geochemistry, zircon U–Pb geochronology, and Hf isotope composition of dioritic rocks from the eastern NQ. Zircon U–Pb dating results indicate that the dioritic rocks were formed during the Middle Triassic (244–240 Ma). The rocks exhibit high-K calc-alkaline characteristics with variable SiO2 (55.25–65.39 wt%) and elevated K2O+Na2O (4.81–6.94 wt%) contents. They show enrichment in LILEs (Rb, Ba, K) and depletion in HFSEs (Nb, Ta, Ti), with slight negative Eu anomalies (Eu/Eu*=0.89–0.97). Zircon εHf(t) values (20.93 to+5.60) and TDM2 ages (0.85–1.72 Ga) suggest mixed sources. Petrographic and mineralogical analysis reveals that the plagioclase phenocrysts exhibit disequilibrium textures (including reverse zoning), primarily composed of andesine and labradorite, with a small amount of oligoclase. The clinopyroxenes are all augites and have high crystallization temperatures (1111–1151 °C). These features, particularly the reverse zoning of plagioclase, support a petrogenetic model involving mantle-derived magma underplating that induced melting of ancient lower crust, followed by mixing of underplated basaltic magma with crust-derived felsic magma. Our results indicate formation in a back-arc extensional setting during subduction of the Zongwulong Paleo-Tethys Ocean.

DOI: 10.1007/s11631-025-00792-9

Source: https://link.springer.com/article/10.1007/s11631-025-00792-9