【摘要】：思泰巖體位于揚子地塊與華夏地塊拼合帶的西南段,對剖析華南區(qū)域構(gòu)造演化具有重要的地質(zhì)意義。思泰巖體主要由輝長巖、輝長閃長巖組成。LA-ICP-MS鋯石U-Pb年代學(xué)分析表明,輝長巖的侵位結(jié)晶時限為(445±1)Ma,屬于加里東期巖漿活動產(chǎn)物。巖石具有高鉀鈣堿性特征;其鋁飽和指數(shù)為0.95~1.99,屬準(zhǔn)鋁質(zhì)-過鋁質(zhì)巖石;巖石具有中等偏高的Mg#值(0.43~0.51)。鋯石的εHf(t)值主要集中在0.39~5.84之間,其一階段模式年齡為1 181~855 Ma,暗示其源區(qū)主要為中-新元古代巖石圈地幔。綜合地球化學(xué)、鋯石Hf同位素組成特征及區(qū)域地質(zhì)資料,認(rèn)為思泰巖體是在陸內(nèi)碰撞造山期后伴隨巖石圈局部伸展-減薄,軟流圈高溫地幔物質(zhì)上涌,從而導(dǎo)致中-新元古代巖石圈地幔物質(zhì)的部分熔融,隨后巖漿發(fā)生上升侵位固結(jié)成巖,在上升侵位的過程中受到少量的地殼物質(zhì)的混染而形成。
[Abstract]:The Sitai rock body is located in the southwest section of the Yangtze and Huaxia blocks, which is of great geological significance to the analysis of the regional tectonic evolution in South China. The dating analysis of zircon U-Pb shows that the emplacement crystallization time of gabbro is (445 鹵1) Ma, which is the product of Caledonian magmatic activity. The rock has the characteristics of high potassium calc-alkalinity, and its aluminum saturation index is 0.95 ~ 1.99, which belongs to the quasi-aluminum-peraluminous rock, and the rock has a moderate high Mg# value (0.43 ~ 0.51). The 蔚 Hf (t) value of zircon is mainly between 0.39 and 5.84, and its model age of 1 181 ~ 855 Ma, indicates that the source region of zircon is mainly Mesoproterozoic lithospheric mantle. Based on geochemistry, zircon Hf isotopic composition and regional geological data, it is considered that the Sitai rock mass is associated with the local extension and thinning of lithosphere after the intracontinental collision orogeny and the upwelling of the asthenospheric high temperature mantle material. This resulted in partial melting of the Mesoproterozoic lithospheric mantle material and subsequent magmatic emplacement consolidation diagenesis, which was formed by the mixing of a small amount of crustal materials during the ascending emplacement process.
【作者單位】： 廣西壯族自治區(qū)地質(zhì)調(diào)查院;中化地質(zhì)礦山總局廣西地質(zhì)勘查院;
【基金】：中國地質(zhì)調(diào)查局項目“桂東-粵西地質(zhì)礦產(chǎn)調(diào)查”(DD20160035)
【分類號】：P588.124

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