扬子陆块西缘四川黎溪地区约1.5 Ga变辉长岩与Columbia超大陆裂解

扬子陆块西缘黎溪—菜子园—通安地区前寒武纪地质体分布广泛，是探讨扬子陆块前寒武纪地质演化的重要载体。对会理黎溪地区变辉长岩开展岩石学、全岩地球化学及锆石U-Pb定年研究。结果显示，黎溪变辉长岩形成于1508±21 Ma；在岩石地球化学组成上，它们属于亚碱性拉斑岩石系列，总体上略微富集轻稀土元素，高场强元素Nb、Ta、Zr、Hf等无明显亏损，大离子亲石元素Ba、Sr等不同程度富集。通过岩石成因分析认为，岩浆在上升过程中经历了一定程度的分离结晶作用，但并未受到明显的地壳混染，母岩浆可能来自软流圈地幔。地球化学和区域地质特征综合分析表明，黎溪变辉长岩与富集洋中脊型玄武岩的地球化学特征相似，可能形成于洋中脊及附近的海山环境，是Columbia超大陆裂解在扬子陆块的响应。

The 1.5 Ga metamorphic gabbro at the Lixi area,S: chuan Province in the western margin of the Yangtze Block: Implications for the breakup of the Columbia supercontinent

Precambrian strata are widely distributed in the Lixi-Caiziyuan-Tong'an area, which is an important window to study Precambrian geological evolution of the western margin of the Yangtze Block.Petrology, whole-rock geochemistry and zircon U-Pb chronology of metamorphic gabbro in the Lixi area of Huili were studied.The results show that Lixi metamorphic gabbro was formed at 1508±21 Ma.In terms of petrogeochemical composition, it belongs to the subalkaline tholeiitic series, and is slightly enriched in light rare earth elements (LREE) on the whole, with no obvious depletion of high field strength elements such as Nb, Ta, Zr and Hf.Under the influence of later weathering, large ionic lithophile elements such as Ba, Sr incompatible elements are enriched in varying degrees.According to the petrogenesis analysis, the magma experienced a certain degree of separation and crystallization during the ascent, but was not obviously contaminated by the crust, and the mother magma might have come from the depleted asthenosphere mantle.The comprehensive analysis of geochemical and regional geological characteristics shows that the geochemical characteristics of Lixi metamorphic gabbro are similar to the E-MORB basalt, which might be formed in mid-ocean ridges or nearby seamount environment as a response to the breakup of Columbia supercontinent in the Yangtze Block.