摘要
昌都地区位于青藏高原碰撞造山带东北部,是西南三江Pb-Zn-Cu-Ag成矿带重要组成部分,区内碳酸盐岩容矿铅锌矿床大量产出,成矿明显受到新生代区域逆冲推覆构造系统控制。拉拢拉铅锌矿床位于昌都地区最具代表性的碳酸盐岩容矿铅锌矿集区西南部,是区内铅锌矿床的典型代表。为了填补三江带昌都地区碳酸盐岩容矿铅锌矿床的研究空白,笔者在对拉拢拉矿区详细地质填图基础上,深入剖析了铅锌矿化成因,建立了铅锌成矿模型。矿区铅锌矿体产于逆冲断层上盘,主要呈透镜体状沿上三叠统甲丕拉组泥页岩和波里拉组灰岩岩性分界面展布,角砾状和网脉状为主要矿石构造,方铅矿、闪锌矿和菱锌矿为主要矿石矿物,矿体控矿要素和产状代表了三江带碳酸盐岩容矿铅锌矿床的一种全新矿床式,命名为拉拢拉式。矿区主要成矿过程划分为硫化物期(I)和硫化物-碳酸盐期(II),两期之间以一期构造活动相隔。I期发育富液相LV流体包裹体和富CO2和CH4的LV流体包裹体两种类型,显微测温显示出低温(130～140℃)、高盐(23%～24%NaCleqv)、中高密度(1.10～1.12g·cm-3)和中低温(170～180℃)、高盐(23%～24%NaCleqv)、中低密度(1.06～1.08g·cm-3)两种特征。两期矿化流体均为Ca2+-Mg2+-Na+-K+-SO42--Cl--F--NO3-卤水体系,其离子含量相近,H-O同位素组成相似(δDV-SMOW为-137‰～-110‰,δ18OV-SMOW为-2.92‰～13.42‰),形成方解石的C-O同位素分布规律一致(δ13CV-PDB为0.9‰～7.2‰,δ18OV-SMOW为9.1‰～26.5‰),揭示矿区至少存在两种流体来源,分别为中低温度、高盐度盆地卤水和由大气降水、地层封存蒸发浓缩海水及区域变质水混合而成的区域流体。两期矿化中矿物S同位素组成相近,硫化物δ34S为负值(-24.7‰～-11.5‰),重晶石δ34S为正值(11.3‰～22.9‰),第三纪石膏δ34S值(2‰～4.7‰)介于二者之间,反映还原硫主要来自生物还原第�
Changdu region, located in the northeastern margin of Tibetan collisional orogenic belt, is the important part of Southwest ‘Sanjiang’ metallogenic belt. Carbonate-hosted Pb-Zn deposits controlled by thrust nappe structures are abundant and with plenty reserves in this region. Lalongla deposit is located in the southwest of the most famous carbonate-hosted Pb-Zn ore concentration area in Changdu region and is a typical representative. The Pb-Zn mineralization of Lalongla deposit is born in the hanging wall of a thrust fault and ore bodies, mainly produced as lens, distribute along a facies transition between mud shale in Jiapeila Formation and limestone in Bolila Formation in Late Triassic. Breccia and mesh-vein are main ore structures and galena, sphalerite and smithsonite are main ore minerals. The ore-control factor and ore occurrence in this deposit represent a new carbonate-hosted deposit type in ‘Sanjiang’ metallogenic belt and then it is named as Lalongla type. The main ore-forming process in this deposit can be divided into Period I （shortened form of sulfide period） and Period II （shortened form of sulfide-carbonate period）, between which a compressing deformation occurred. Two kinds of fluid inclusion including LV inclusion rich in liquid and LV inclusion rich in CO2 and CH4 occur in Period I. A microthermal testing work suggests two kinds of hydrothermal fluids in this period, which are with low temperature （130~140℃）, high salinity （23%~24% NaCleqv） and middle to high density （1.10~1.12g·cm-3） nature and with middle to low temperature （170~180℃）, high salinity （23%~24% NaCleqv） and middle to low density （1.06~1.08g·cm-3） nature, respectively. For the two periods, the liquid parts of hydrothermal fluids both belong to Ca2＋-Mg2＋-Na＋-K＋-SO42--Cl--F--NO3- system and the ion contents, H-O isotope composition （-137‰^-110‰ for δDV-SMOW and -2.92‰~13.42‰ for δ18OV-SMOW）, C-O isotope composition of calcite （0.9‰~7.2‰ for δ13CV-PDB and 9
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第4期1407-1426,共20页
Acta Petrologica Sinica
基金
国家"973"项目(2009CB421007
2011CB403104)
国家自然科学基金项目(U0933605)
国际地质对比计划(IGCP/SIDA-600)联合资助
