【作者】 叶霖；

【导师】 李朝阳；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 矿床地球化学， 2004， 博士

【摘要】 稀矿山式铜矿是指赋存在昆阳群因民组地层中的铜铁矿床，其大地构造背景属于元古代裂谷带，大陆裂谷是超大型铜等多金属矿形成和分布的有利环境，在裂谷下部常发育异常地幔和岩浆源，裂谷空间上的多层次性使矿床具有明显垂向分带特征，其演化时间的长期性、脉动性和继承性便于多期成矿作用相互叠加、矿质的高度聚集。稀矿山式铜矿以落雪矿区稀矿山矿段最为典型，主要分布在因民落雪大乔地—稀矿山、滥山、磨子山，滥泥坪6—4巷、白锡腊和拖布卡地区。该类矿床广布于康滇地轴南段东川、武定—罗茨、元江、易门狮子山、金沙江南岸的花生坪、红门厂等地，已知中型铜矿床1处（稀矿山）、中型铁矿床2处（鹅头厂、笔架山）、小型铜（铁）矿床多处，上世纪90年代易门狮子山该类矿床的发现，表明该类矿床在东川-易门具找矿潜在远景。 本文通过对东川矿区稀矿山式铜矿的常量元素、微量元素、包裹体、同位素及同位素定年等地球化学研究，获得以下认识： 1．东川矿区地层（包括其下覆基底）和晋宁期碱基性岩中Cu等成矿元素背景值较高，且在蚀变过程中均能析出Cu等成矿元素。矿床中Cu等成矿物质来源复杂，以深源为主，部分来源于地层（因民组紫色层和落雪组白云岩）及基底地层；矿区内的退色蚀变作用可能是混合流体碱质交代改造作用的结果，对铜矿形成影响明显，是铜矿化的标志； 2．该类矿床成矿流体属于中高温、中高盐度、高密度Na⁺（K⁺）Ca²⁺—SO₄^2-（Cl^-）型，以深部岩浆水为主，混有大量海水和变质水。矿床中发现了富N₂包裹体，可能是矿床形成时，深大断裂活动、碱基性岩浆带来地球深部（上地幔和下地壳）物质并形成的成矿流体，在氧化-去挥发分作用过程中所形成； 3．铁矿体被铜矿体包围，铁矿石被铜矿细脉穿插，说明铜矿化的形成晚于铁矿化。黄铜矿单矿物的Re-Os同位素年龄研究表明其成矿年龄为826±230Ma，接近矿区碱基性岩年龄，与昆阳裂谷内其它类型铜矿成矿时代相当，均属于晋宁—澄江期； 4．东川矿区晋宁-澄江期碱基性岩侵入活动明显，常作为因民组复杂角砾岩胶结物和岩脉（体）产出，多分布于深大断裂及其派生的次级构造附近，明显受南北向小江深大断裂走滑运动引起的右行旋扭及其派生构造控制，与“落因破碎带”和“铜矿分布”较吻合，均为“Z”字形。表明东川矿区铜矿形成与深大断裂及其派生次级构造和晋宁—澄江期碱基性岩侵入活动关系密切； 5．昆阳裂谷内的多数铜矿同位素成矿年龄多集中在9.0亿～6.5亿年之间，属于晋宁-澄江期，与Rodina大陆裂解时限相当。表明裂谷内铜矿床的形成可能与Rodinia大陆裂解有关。 因此，总结东川稀矿山式铜矿成矿模式为沉积（Fe、Cu）—热液叠加（Cu）改造： 晋宁-澄江期，小江深大断裂发生走滑运动，在东川矿区造成右行旋扭及其派生构造，形成“Z”字形落因破碎带，同时来自深源（下地壳或上地幔）碱基性岩浆侵入，不仅带来了大量Cu等成矿物质，更重要的是提供了热源，促使地层水（落雪组白云岩和因民组紫色层）循环，与富碱（Na和K）岩浆水混合，形成富碱中高温高盐度流体。因民组紫色层与其底部角砾岩接触带，具有较高的空隙度和渗透率，有利于成矿流体的运移和成矿。在这种混合流体作用下，地层中Cu等成矿物质析出，叠加改造了初始铜矿化，最终形成稀矿山式铜矿。更多还原

【Abstract】 Xikuangshan Type Copper Ore Deposit named those Fe-Cu deposits hosted in Yinmin Formation, Kunyang group, which located in Kunyang rift valley and the edge of southwest yangzi platform. The best example is Xikuangshan allotment, Luoxue ore area, Dongchuan, Yunnan. The type deposit spread in south Kunyang rift valley, include Dongchuan, Wuding-Luoci, Yuanjiang, Yimen, Huashengping, Hongmenchang and so on. 90’s it was found in shizishan, yimen, indicated that the type deposit is well explorative prospect in Dongchuan-yinmen.By sum up the data of trace elements, isotopic elements, fluid inclusions and minerogenetic age et al., the following new knowledge are acquired:a) The Cu background of stratum and Jinningian alkali basite is abnormal high, which could be liberated from those rocks during alteration. Cu et al. minerogenetic elements, which main came from magmatic rock, some from stratum (Yinmin Formation and Luoxue Formation) and its basement rocks. Discolorative alteration, the mark of Cu mineralization, is the result of alkali fluid metasomated stratum rocks.b) Ore-forming fluid belong to Na+ (K+) Ca2+-SO42- (CD type fluid of middle-high temperature, salinity, and high density. It was consist of magmatic water came from deep source, some seawater and metamorphic water. N2 -rich inclusions were first founded in ore area; it may form by upper mantle or lower crust material during oxidation-devolatilization reactions.c) Copper ore body surrounded iron ore body; Iron ore were interpenetrated by copper ore stringer vein, which indicated that copper form late than iron. Metallogeneti age is 826± 230Ma, similar with the age of alkali basite and age of other copper deposit in Dongchuan ore area, which belong to Jinningian.d) The invasion of Jinningian-chengjiangian alkali basite were unambiguous, the distribution of those rocks form ’Z’ in shape, which similar with Luoyin fracture zone and the distribution of copper deposit. It shows that copper deposits were controlled by discordogenic fault and its derived sub-structure, and there are relationship between copper deposit and Jinningian-chengjiangian alkali basite.e) Most of minerogenetic age of copper deposit, which located in Kunyang rift valley, belongs to Jinningian-chengjiangian (between 900-650Ma), similar with the time limit of breaking- up of Rodinia. It indicates there are close relationship between the forming of copper deposit in Kunyang rift valley and the breaking-up of Rodinia.The minerogenetic model of Xikuangshan type copper deposit can be concluded that: In Jinningian-chengjiangian, the activity of Xiaojiang discordogenic fault form dextrorotation sub-structure in Dongchuan ore area. Luoyin fracture zone were formed (’Z’ in shape). Alkali basite, which came from upper mantle or lower crust, invaded through those structure, which not only bring Cu et al mineralizing elements, but also the most important is that thermal energy. It cycled the formation water (Yinmin Fonnation and Luoxue Formation), and form alkali-rich, middle-high temperature and salinity fluid mixed with alkali-rich magmatic water. There were high rate of percolation and well voidage in the contact zone between Yinmin purple stratum and Yinmin rubblerocks, which is in favor of the transposition and mineralization of minerogenetic fluids. Cu et al minerogenetic elements were liberated from stratum by the affection of the mixed fluid, overprinted and alternated the original mineralization, and form Xikuangshan type copper deposit.更多还原