草桃背矿床白垩纪橄榄玄粗岩与铀成矿关系
Relation Between Cretaceous Shoshonite and Uranium Metallogenesisin Caotaobei Uranium Deposit

张运涛 ¹ 裴荣富 ¹ 于波 ¹ 陈永飞 ² 杨东生 ³ 邱小平 ⁴

文摘	赣南会昌断陷盆地沿石城-寻乌深断裂分布一条白垩纪橄榄玄粗岩系列的火山岩带。草桃背大型铀矿床内出露大富足岩体中-粗粒黑云母花岗岩及早白垩世晚期到晚白垩世早期橄榄玄粗岩系列火山岩。大富足花岗岩体岩石w(SiO_2)平均为74.67%,碱总量(w(K_2O+Na_2O))平均为7.99%,w(K_2O)>w(Na_2O),w(CaO)平均为0.54%,w(Al_2O_3)>w(CaO+Na_2O+K_2O),属高钾钙碱性岩石系列。橄榄玄粗系列火山岩岩石w(SiO_2)为45.78 %~59.78 %,w(K_2O+Na_2O)平均为7.37%,K_2O/Na_2O平均为1.02,w(TiO_2)平均为0.86%, 全铁质量分数平均为7.09%,属偏碱性橄榄玄粗质火山岩类。草桃背铀矿床赋矿岩性为橄榄玄粗岩、碎裂花岗岩及隐爆角砾岩。赋存于碎裂花岗岩及隐爆角砾岩中铀矿石化学成分,与围岩花岗岩成分相似;赋存于橄榄玄粗岩中铀矿石,Fe_2O_3+Fe_2O、CaO、MgO不同程度地带出,w(SiO_2)明显增高,表明橄榄玄粗岩在成矿过程中,通过输出大量Fe、Mg、Ca等阳离子而促进铀离子从含矿溶液中沉淀。草桃背矿床的铀矿化与充填在草桃背火山口的橄榄玄粗岩关系密切,在时间上相近、在空间上相伴、在成生上相关,受橄榄玄粗岩岩浆系列热动力的影响,铀元素发生活化、转移或物质交换而成矿,成岩成矿时代属早白垩世晚期到晚白垩世早期。从草桃背铀矿床岩石学、地球化学及赋矿特征入手,总结了铀成矿是富铀矿的花岗岩基底、北东向构造及火山作用结合的产物,橄榄玄粗岩提供热源,并指出半岭、上寮、小富足等地段是寻找草桃背式铀矿床的极有利地区。
其他语种文摘	The Huichang faulted basin is located in southern Jiangxi, where appear shoshonite rock series of Cretaceous along Shicheng-Xunwu deep fault. The shoshonitic rocks host a variety of significant mineral deposits, such as iron, copper, gold, lead, zinc, silver and uranium deposits in southeastern China, including hydrothermal uranium deposits at Xiangshan and Caotaobei respectively in northeastern and southern Jiangxi Province. The Caotaobei deposit lies in the Hecaokeng district (ore field). The host rocks for ore of the Caotaobei uranium deposit are primarily medium to coarse grained porphyritic biotite monzogranites of the Dafuzu intrusion and Cretaceous shoshonitic volcanic rocks. The Dafuzu pluton corresponds to calc alkaline S type granites, with high content of SiO2 (averaging 74.67%), strongly peraluminous ((Al_2O_3)>(CaO+Na_2O+K_2O)), high total alkalis (average (K_2O+Na_2O) content 7.995%), high content of CaO content (average CaO content 0.54%). The shoshonite series are characterized by: rich SiO_2 (varying 45.78 % to 59.78 %),high K_2O/Na_2O (average 1.02), high total alkalis (average (K_2O+Na_2O) content 7.37%),low TiO_2 content (average 0.86%), low iron content (average ∑Fe 7.09%). Uranium mineralization occurs predominantly as veinlets and massive and disseminated replacement ores in shoshonites, granite and cryptoexplosive rocks, among them, the chemical composition of uranium ore in granite and in cryptoexplosion rocks are similar with host granite. Whereas the Fe_2O_3+Fe_2O,CaO and MgO leached out and SiO2 enriched in the ores hosted in the shoshonitic volcanic rocks, indicating U precipitated from uraniferous solution by cations (such as Fe,Mg,Ca) leached out during shoshonite series metallogenesis. Uranium mineralization within Caotaobei deposit are simultaneously with shoshonitic rocks in the Caotaobei crater, and they are closely related both in space and in genesis. Affected by thermal activities from shoshonitic magma, uranium elements activated and transferred to form uranium ores at the late stage of Early Cretaceous to early stage of Late Cretaceous. Based on petrographic, geochemical and ore host features studies, an integrated model of the entire mineralized system is summarized, in which uranium mineralization is related to cryptoexplosive breccias caused by overpressured fluids exsolved from crystallizing shoshonitic magma below the Caotaobei caldera and simultaneously leached ore metals from the host volcanic rocks and the caldera basement (the Dafuzu granite batholith). Several potential targets such as Banling, Shangliao, Xiaofuzu are delineated for Caotaobei type uranium deposit.
来源	吉林大学学报. 地球科学版 ,2013,43(5):1423-1435 【核心库】
关键词	橄榄玄粗岩 ; 铀矿床 ; 火山口 ; 草桃背 ; 火山岩
地址	1. 中国地质科学院矿产资源研究所, 北京, 100037 2. 江西省核工业地质局二六四大队, 江西, 赣州, 341000 3. 中国科学院广州地球化学研究所, 广州, 510640 4. 中国地质科学院地质研究所, 北京, 100037
语种	中文
文献类型	研究性论文
ISSN	1671-5888
学科	地质学
基金	国家科技部支撑计划项目 ; 江西省国土资源厅项目
文献收藏号	CSCD:4970329