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    湖南川口岩体型钨矿赋矿花岗岩地球化学特征及LA-ICP-MS锆石U-Pb定年

    Geochemical characteristics and LA-ICP-MS zircon U-Pb dating of ore-bearing granite of Chuankou intrusion-related tungsten deposit, Hunan Province

    • 摘要: 川口矿田钨矿床产于湖南衡阳川口岩体的外接触带及岩体内部,矿床类型主要有岩浆热液石英细脉带型和石英大脉型。近年川口矿田取得了重大找矿突破,并发现了新类型的岩体型钨矿。本文对川口岩体型钨矿床的黑云母二长花岗岩及赋矿的白云母二长花岗岩分别进行了LA-ICP-MS锆石U-Pb定年和岩石地球化学特征研究,获得川口岩体的成岩年龄为(223.1±0.78)Ma,MSWD=0.98,n=24,岩体型钨矿成矿年龄为(224.6±1.31)Ma,MSWD=0.33,n=9,为印支期成岩成矿。川口花岗岩具有高SiO2,富K2O+Na2O,低CaO、MgO的特点,属于过铝质高钾钙碱性系列S型花岗岩,形成于碰撞环境下弱挤压构造体制。川口岩体稀土总量(ΣREE)整体较低,轻稀土相对较富集,具有强烈的负Eu异常,富集大离子亲石元素Ba、K和高场强元素Ta,而亏损大离子亲石元素Sr和相容元素P、Ti等,表明该岩体各阶段花岗岩来自同一岩浆源,且经历了高度演化。赋矿花岗岩更低的δEu值及(La/Yb)N值,表明其结晶分异程度更高。

       

      Abstract: The tungsten deposits in the Chuankou orefield occur in the outer contact zone and the inner part of the Chuankou pluton. The deposit types are mainly quartz-veinlet belt type and quartz-big vein type of magmatic-hydrothermal origin. In recent years, a breakthrough in prospecting has been made in the Chuankou orefield, and a new type of intrusion-related tungsten deposits has been found. In this paper, LA-ICP-MS zircon U-Pb dating and rock geochemical characteristics of biotite adamellite and ore-hosting rock muscovite monzogranite are studied. The diagenetic age of the Chuankou pluton is (223.1±0.78) Ma, MSWD=0.98, n=24, and the ore-forming age of the intrusion-related tungsten deposit is (224.6±1.31) Ma, MSWD=0.33, n=9, all of which are in Indosinian period. The Chuankou granite is characterized by high SiO2 and K2O + Na2O, low CaO and MgO. It belongs to the peraluminous high-K calc-alkaline series S-type granites, which was formed under the weak compression tectonic system in the collision environment. The Chuankou pluton is characterized by low total REE (∑REE), relatively rich LREE, strong negative Eu anomaly, enrichment of large ion lithophile elements Ba, K, and high field strength element Ta, and depletion of large ion lithophile elements Sr and compatible elements P, Ti, which indicates that the granites of each stage of the granites came from the same magma source and experienced a high degree of evolution. Compared with other granites, the ore-bearing granite (muscovite monzogranite) with lower δEu value and (La/Yb)N value has a higher crystallization differentiation degree.

       

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