【摘要】 江西相山火山盆地发育我国第一大、世界第三大火山岩型铀矿田,盆地盖层主要为早白垩世流纹英安岩和碎斑熔岩,这两套火山岩亦是研究区内主要的赋矿岩石,与铀多金属矿化有关的垂向蚀变幅度达千米。近年来,相山铀矿田地质勘查取得了令人瞩目的进展,然而对于矿床的成因及产状等方面仍存在争论,部分原因在于,对流纹英安岩和碎斑熔岩的火山机构研究不够深入。通过对相山矿田的遥感地质解译、碎斑熔岩流动构造测量、磁化率各向异性(AMS)及大地电磁测量(MT)等研究,获得火山通道位置。相山火山盆地流动构造不发育,根据火山集块岩、熔岩中出露的变质岩捕掳体及其长轴统计,结合AMS数据,指示鹅湖岭期碎斑熔岩主火山口位于相山顶,河元背、严坑、柏昌和如意亭为4个次级火山口,而书塘地区可能是打鼓顶期流纹英安岩的火山通道所在。这些推测的火山口在遥感影像上得到环形、放射状构造的印证。相山火山盆地19条MT剖面显示:盆地基底变质岩系与上覆火山岩盖层之间呈连续的水平低阻异常带,不整合界面清晰;打鼓顶组火山岩呈似层状产出,主要分布于盆地西部,并在河元背-船坑-杏树下一带识别出近东西走向的厚层流纹英安岩凹槽;鹅湖岭组火山岩总体呈蘑菇状,中心位置(相山主峰)发育自下而上贯通式的低阻异常,推测为鹅湖岭组碎斑熔岩喷发的通道相(火山颈相)。综合研究表明,相山地区打鼓顶期主要火山通道位于相山顶或其西侧书塘地区,可能存在河元背次级岩浆通道;鹅湖岭期火山活动主岩浆通道位于相山顶,次岩浆通道位于河元背、阳家山、严坑和柏昌,岩浆通道具有继承性和发展性。更多还原

【Abstract】 The Xiangshan volcanic basin in Jiangxi province is the largest volcano-type uranium deposit in China and the third largest in the world. Having been investigated for over 60 years, the total drilling core in the basin exceeds 2 million meters. The main lithology of the basin is the Early Cretaceous rhyodacite and porphyroclastic lava,accompanied with intrusive rocks. The volcanic rocks are the major ore-bearing rocks, and alteration related to the uranium and associated Pb-Zn mineralization is up to 1000 meters thick vertically. In recent years, remarkable progress has been made in geological exploration. A number of new deposits and mineralization sites have been found, and the old ones continuously expanded. However, it is still controversy regarding the origin and location of deposits, mainly because of the volcanic calderas location of rhyodacite and porphyroclastic lava is still unclear. Remote sensing,magnetic susceptibility anisotropy(AMS) and magnetotelluric(MT) measurements of rhyodacite and porphyroclastic lava in the basin have been conducted to determine the volcanic calderas locations. The results show that the flow structure of the Xiangshan volcanic basin is not well developed. According to the outcrops of volcanic agglomerate and metamorphic rocks in the field, it seems that there are three volcanic calderas for the porphyroclastic lava. The AMS data suggest that the craters located at the summit of Xiangshan, Yankeng, Heyuanbei, Ruyiting and Baichang, whereas the Shitang area may be the volcanic vent of rhyodacite. The 19 MT sections across the volcanic basin show that there is a continuous horizontal low resistivity anomaly belt between the metamorphic basement and the overlying volcanic covers. In the area of Heyuanbei-Chuankeng-Xingshuxia, a thick east-west-strike rhyodacite dimple is identified. The main uranium deposits are distributed in the concave or nearby. The general morphology of volcanic rocks of the Ehuhuling Formation is mushroom-shaped, and is thick in the central part of the basin. A low-resistivity anomaly from bottom to top is found within a radius of about 2 km from the Xiangshan main peak. It was thought to be eruption of the channel phase(volcanic neck phase). The volcanic neck was steep tubular, dip to the south. The late granite porphyry was a combination of dikes and bedrock, forming an annular rock mass opening to the west. On the whole, the volcanic calderas of rhyodacite was located in the Xiangshan main peak or Shutang area, and there may be a Heyuanbei secondary magma channel. The main magmatic channel of the Ehulling period is located at the Xiangshan main peak and sub-magma channel located in Heyuanbei, Yangjiashan(Furongshan), Yankeng and Bochang.更多还原