摘要
勐兴铅锌矿床是滇西保山地块内系列低温热液矿床中的典型代表,但地质科研工作相对薄弱。由于方解石是该矿床中分布广泛且与热液活动息息相关的重要脉石矿物,其形成贯穿整个成矿过程,故对其C-O同位素及稀土元素组成特征进行系统研究,以便探讨矿床成矿流体来源及演化。结果显示,该矿床两阶段方解石的δ13 C PDB和δ18 O SMOW值与海相碳酸盐岩较为接近,且从阶段Ⅰ→阶段Ⅱ呈微弱下降趋势,表明成矿流体中的C主要来源于围岩碳酸盐岩的溶解,阶段Ⅱ成矿流体在与围岩反应之前可能已经发生CO 2热液去气作用;阶段Ⅰ方解石的稀土总量、特征参数及配分模式与结晶灰岩较为一致,而阶段Ⅱ方解石与生物碎屑灰岩较为相似,表明阶段Ⅰ方解石中的REE主要来源于结晶灰岩,而后生物碎屑灰岩对阶段Ⅱ方解石中的稀土贡献较大。以上数据及其矿床地质特征均显示该矿床为MVT型铅锌矿床,结合区域构造演化,认为勐兴矿床的形成与中特提斯洋闭合后腾冲地块与保山地块陆陆碰撞挤压密切相关。
The Mengxing Pb-Zn deposit,located in the Baoshan block of western Yunnan,is a representative of series of epithermal deposits,while less geological research on it has been made.Calcite is one of the major gangue minerals in this deposit and widely distributed and closely related to hydrothermal activity.So this work analyzes its C-O isotopes and REE to explore the origin and evolution of ore-forming fluid.Research shows that theδ13 C PDB andδ18 O values of calcite of two stages are close to the marine carbonate with a weak downward trend from stage I to stage II,implying that the C element in the ore-forming fluid was mainly produced by the dissolution of wall-rock carbonate and the downward trend in stage II was caused by CO 2 degassing before fluid-rock interaction.The total rare earth amount,characteristic parameters and chondrite-normalized REE patterns of calcite of stage I are well consistent with crystalline limestone,while that of stage II is similar to bioclastic limestone,indicating that the REE of stage I calcite was derived from the crystalline limestone.However,calcite of stage II in the bioclastic limestone contributed more to the REE.Both the above data and other geological characteristics suggest that the deposit belongs to MVT-type.Combined with the regional tectonic evolution,we consider that the deposit was formed under the background of continental collision and compression between the Tengchong block and Baoshan block after the closure of the Meso-Tethys.
作者
刘锦康
邓明国
毛政利
王丹
耿齐卫
LIU Jinkang;DENG Mingguo;MAO Zhengli;WANG Dan;GENG Qiwei(School of Education Science,Baise University,Baise,Guangxi 533000;Faculty of Land Resource Engineering,Kunming University of Science and Technology,Yunnan,Kunming 650031;School of Management Science and Engineering,Baise,Guangxi 533000;Yunnan Instituteof Geology&Mineral Resources Exploration,Kunming,Yunnan 650051)
出处
《地质与勘探》
CAS
CSCD
北大核心
2021年第4期852-864,共13页
Geology and Exploration
基金
国家自然科学基金项目(编号:41762009)
2021年度广西高校中青年教师科研基础能力提升项目(编号:2021KY0736)联合资助。
