摘要:后山岩体与茂林岩体处于下扬子江南隆起带内，沿江南断裂带两侧分布。二者岩性均以花岗闪长岩为主，主量元素特征显示其属于高钾钙碱性、准铝质—过铝质系列的Ⅰ型花岗岩；微量元素原始地幔标准化蛛网图见Nb、Ta、Ti谷；稀土元素显示其富集轻稀土而亏损重稀土元素，球粒陨石标准化曲线呈现右倾、Eu负异常。两个岩体地球化学特征显示其形成的花岗闪长岩岩浆主要源于地壳物质的部分熔融，可能有少量地幔物质的参与。利用锆石Ti温度计、长石温度计及黑云母温压计获得：后山岩体岩浆侵位温度约为660℃～780℃，结晶温度约为652℃～683℃，成岩温压： T=470℃～653℃，P=0.14～0.25 GPa，大约形成于4.6～8.3 km的深度；茂林岩体岩浆侵位温度约为679℃～768℃。结晶温度约为685℃～728℃，成岩温压：T=496℃～591℃，P=0.15～0.20 GPa，大约形成于5.0～6.6 km的深度。后山岩体花岗闪长岩LA-ICP-MS锆石U-Pb测年结果140.4±1.5 Ma，茂林岩体花岗闪长岩137.6±1.6 Ma、137.9±1.6 Ma、135.4±1.4 Ma，均属于早白垩世，是江南隆起带内燕山期早期岩浆活动的结果。两个岩体地球化学特征反映出其形成于区域上153～135 Ma时期的挤压向伸展过渡的构造环境下，代表了这一时期以太平洋构造体制主导下的应力作用开始在下扬子地区江南隆起开始逐渐发生转换。
关键词: 江南隆起带/
Ⅰ型花岗岩/
地球化学/
LA-ICP-MS锆石U-Pb测年
Abstract:Houshan and Maolin plutons are located in Jiangnan uplift belt and occur along Jiangnan fault zone. Both belong to typical high-potassium calc-alkaline series, quasi-aluminous-peraluminous Ⅰ-type granite. See Nb, Ta and Ti valleys for the standardized cobweb map of the original mantle of trace elements. Rare earth elements showed that they enriched light rare earth elements but lost heavy rare earth elements, and the standardization curve of chondrite showed a right-leaning trend, showing Eu negative anomaly. The granodiorite magma of Houshan and Maolin plutons is mainly derived from partial melting of the crust and may be involved in a small amount of mantle material. Zircon Ti thermometers, feldspar thermometers and biotite thermometers were obtained:The emplacement temperature of Houshan is 660℃~780℃, the crystalline temperature is 652℃~683℃, the diagenetic temperature and pressure are:T=470℃~653℃, P=0.14~0.25 GPa, formed at the depth of 4.6~8.3 km; the intrusion temperature of Maolin is about 679℃~768℃. Crystalline temperature is about 685℃~728℃, diagenetic temperature and pressure:T=496℃~591℃, P=0.15~0.20 GPa, formed at the depth of 5.0~6.6 km. The environment of the two plutons is low temperature and pressure, which is similar to the early stage granite formation environment in the Jiangnan uplift zone. The LA-ICP-MS zircon U-Pb dating of the Houshan granodiorite is (140.4±1.5 Ma) and Maolin(137.6±1.6 Ma, 137.9±1.6 Ma, 135.4±1.4 Ma). They belong to Early Cretaceous magmatism of Early Yanshanian magmatism in Jiangnan uplift belt. The tectonic background shows that it was formed in the period of 153~135 Ma in the region during the transition period from compression to extension, which represents the gradual transformation of the stress under the Pacific tectonic regime in this period.
Key words:Jiangnan uplift belt/
Ⅰ-type granite/
Geochemical/
Zircon LA-ICP-MS U-Pb
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