新平大红山—元江撮科铜铁多金属成矿系列及成矿预测

【作者】 邓明国；

【导师】 秦德先； 李文昌；

【作者基本信息】 昆明理工大学 ， 矿产普查与勘探， 2007， 博士

【摘要】 本博士论文“新平大红山-元江撮科铜铁多金属成矿系列及成矿预测”是结合国土资源部“西南三江云南段有色金属基地勘查”所属的“云南元江撮科-新平地区铜铁矿评价”项目（编号:资（2006）003-04）的科研需要而选题。本文应用成矿系列理论及综合信息成矿预测相结合的方法,在广泛收集区域地质矿产、物化探、遥感、科研、勘查资料和吸取前人成果和认识的基础上,从野外大量的观察研究入手,厘定了研究区三大成矿系列,并以第一成矿系列—与早元古代富钠质火山-沉积岩有关的变质铁、铜、金成矿系列—“大红山式”铁铜矿床为重点解剖对象,对早元古代大红山群的含矿性、岩石学、变质火山岩形成的构造环境等方面进行了综合地质研究;进行了矿床地质、地球化学特征研究及岩石的微量元素、稀土元素、同位素地球化学、流体包裹体和成矿规律等的系统研究工作;对区域成矿地质背景、地球物理特征、地球化学特征和遥感影像特征进行详细研究的基础上,在计算机及高新技术（GIS）支持下,对新平大红山—元江撮科铁铜多金属成矿带开展了综合信息成矿预测研究,获得了如下的主要成果:（1）确立了研究区地质构造演化及其对成矿的控制。研究区所处的康滇地轴成矿带经历了漫长的演化历史,裂谷多旋回带来了成矿多旋回,并形成了不同类型的矿产。“大红山式”铁铜矿床产于陆缘海型初生拗拉槽中,裂谷作用造就了相对封闭还原的海盆地,与矿床的形成密切相关。在其深谷中沉积了大红山群,来自古陆核深部上地幔岩浆柱的物质侧向上涌,于拗拉槽中爆发火山活动,大红山火山岩型铁铜矿床即产于该拗拉槽的细碧角斑岩-陆屑-碳酸岩建造的富钠质熔岩与凝灰岩中,其火山岩属洋脊拉斑玄武岩,具有铁铜矿成矿专属性。（2）厘定了研究区的成矿系列。在时间上由与早元古代富钠质火山—沉积岩有关的变质铁、铜、金成矿系列→与中元古代（喷流沉积）沉积改造有关的浅变质铁、铜、稀土成矿系列→与中生代早期沉积—改造作用有关的铜矿成矿系列,全面揭示了各个成矿系列的矿床类型、控矿规律及找矿方向。考虑3个成矿系列的典型代表,划分出大红山式和撮科式,落雪式和易门式以及晚三叠统砂砾岩中沉积-改造铜矿类型,并对其进行了解剖,为各个成矿系列的建立提供了实证研究。（3）重点研究了“大红山”式铁铜矿床的岩石地球化学特征。根据岩石地球化学研究,确定铁铜矿与富钠火山岩密切相关,含矿围岩、矿体及次火山岩具有近似或相同的形成条件和环境,矿床为与海底火山喷发作用有关的偏碱基性火山岩成矿系列;微量元素统计分析表明:矿石与围岩微量元素组合基本相同,说明二者具有相同的物质来源:稀土元素配分模式表现为轻稀土富集的陡倾斜曲线和Eu的负异常,说明蚀变和变质已使原岩中的斜长石受到了强烈改造,Ce总体为弱负异常,（La/Sm）＞1,具有洋中脊T型玄武岩特征,稀土总量普遍较低,且明显富集轻稀土,属轻稀土富集型。（4）对“大红山式”铁铜矿床成矿温度、成矿物质来源、成矿流体和成矿时代进行了系统研究。包裹体均一温度为102～370℃之间,可能存在两个成矿阶段:早期成矿阶段均一温度为290～330℃,盐度为16～32wt%,pH值为3.7～3.0,logfs₂为-70.2,logfo₂为-26.55,logfco₂为3.3～1.5;晚期成矿阶段为160～250℃,盐度为13.8～45wt%,pH值为4.5～3.4,logfs₂为-11.04,logfo₂为-34.37,logfco₂为4.63～3.9;铅同位素资料显示,成矿物质为不同源、不同环境、不同时间形成的混合铅;硫同位素分析表明,硫源主要来自海水硫酸盐的还原作用,部分来自火山喷发作用从深部带来的地幔硫,是火山与海水两种来源的硫混合而成;从δ¹⁸O_H20和δD_H20值判断,本区成矿流体水的来源比较复杂,火山沉积成矿期介质水的来源主要为原生岩浆水,并受到一定程度海水的影响,后期的区域变质改造过程中,则逐渐演化成岩浆水、变质水和大气降水混合效应的成矿流体。同位素年代学研究:从K/Ar同位素年龄看,主要集中在800Ma±20Ma,反映“大红山式”铜铁矿床后期变质改造的事件,代表了晋宁运动期间火山作用、变质作用及铀矿化的时间,也是大红山铜矿床的改造年龄。（5）运用成矿系列理论指导找矿预测。根据成矿系列阐述的矿床在空间上的分布和时间上的演化规律,总结了大红山岩群寻找铁铜多金属矿床的5大控矿因素和8大成矿预测标志,为综合信息成矿预测奠定了理论基础。（6）重点研究了“大红山式”铁铜矿床的地质-物化特征,建立了该类型矿床的成矿模式。利用多元成矿信息理论对研究区成矿地质背景、地球化学、地球物理及遥感地质特征进行了全面的论述,总结了研究区内“大红山式”铜铁矿床找矿勘查的地球物理及地球化学勘查模型。利用基于GIS的多元地学成矿信息对早元古代大红山群和昆阳群进行了找矿靶区定位预测,指出了找矿远景区,为矿山的找矿勘探指明了方向。更多还原

【Abstract】 The doctoral dissertation, The Iron and Copper Poly-metal Metallogenic Series and Minerogenetic Targeting of Xinping Dahongshan-Yuanjiang Cuoke Area, is based on the scientific research requirements for the project, Assessment of the Copper and Iron Minerals in Yuanjiang Cuoke-Xinping Dahongshan Area, Yunnan, a sub-project of The Base Survey for Non-ferrous Metal at Yunnan Section of the Southwest Three Rivers sponsored the Ministry of Land and Resources, P.R.C.In this paper, an approach combining metallogenic series theory with comprehensive information minerogenetic prognosis method is adopted, and based on the widely collected data including geological mineral, geophysical and geochemistry prospecting, remote sensing, scientific research, survey and the result and knowledge of predecessors and a large amount of field observation and research, three large metallogenic series （or sub-series） have been collated and stipulated. In the first metallogenic series—the iron, copper and gold metallogenic series relevant to albite-rich volcano-volcanic sedimentary function of early Proterozoic, Dahongshan-type iron and copper ore deposit, a typical mineral deposit, is selected as the important dissection object. Comprehensive geological studies have been conducted on ore-bearing potential, petrology and the tectonic environment of the metamorphic volcanic rock formation. Other research work includes the systematic studies on deposit, irrespectively geologic of deposit, geochemical features and on the microelements, REE, geochemical characteristics of the isotopes, fluid inclusions and minerogenetic regularities, etc. On the basis of the detailed studies of the minerogenetic geological background, geophysical and geochemical characteristics and remote sense image, with the computer and high-tech technology （i.e. GIS）, metallogenic prognosis researches of comprehensive information has been conducted on the iron and copper poly-metal minerogenetic belt of Xinping Dahongshan-Yuanjian Cuoke, the following important results have been achieved:1. The evolution of geological tectonics and its control over minerogenesis in this research region are established. The minerogenetic belt of Kang-Dian Axis in the study area has gone through a very long evolution history, and the polycyclic rifting in the region has brought about minerogenetic polycycle, thus forming varieties of minerals. Dahongshan-type copper and iron ore deposit is formed in the nascent aulacogen of the continental margin. The rifting has resulted in the marine basin with relative closing, which is closely related to the formation of the deposits. At the deep valley of the basin, with the surging effect of the materials of upper mantle magma column from the paleo-land core, volcanic activities have broken out in aulacogen. Dahongshan copper-iron ore deposit of the volcanic rock type is formed in such albite-rich lava and tuffs constructed by the spilitic keratophyre-terrigenous clastic sedimentary-carbonate formation, both of which are mid-ocean ridge basalt with exclusive copper-iron minerogenetic property.2. The metallogenic series in the study area have been collated and stipulated. These metallogenic series can approximately be arrayed in accordance with chronologically evolved order as iron, copper and gold metallogenic series relevant to early Proterozoic albite-rich volcanic sedimentary formation, copper, iron and REE metallogenic series relevant to early Mesoproterozoic sedimentary-reconstructing transition, and sedimentary-reconstructing copper deposit metallogenic series of the glutenite in late Mesozoic Erathem. These overall series reveal the types of the deposits, ore-controlled regulations and prospecting orientation. The typical cases of the three metallogenic series are considered, Dahongshan type, Cuoke type, Luoxue type, Yimen type and sedimentary-reconstruct copper deposit type of Late Triassic Series in sand and conglomerate are partitioned, and the typical ore deposits are dissected, which provides empirical study for each metallogenic series.3. The petrology and geochemistry characteristics of Dahongshan iron-copper are disclosed in the paper. The petrochemical study shows that the iron-copper deposit is closely related to albite-rich volcanic rocks. The ore-bearing wallrock, ore body and sub-volcanic rock have near or same formation conditions and environments, and the ore deposit is a metallogenic series of alkalescent basic volcanic rock relevant to the eruption action of submarine volcano. The statistical analysis of the microelements reveals that the microelement combination of ores is nearly the same as that of wallrock, which shows that both of them have the same material source. The distribution pattern of the REE embodies the steep tilting curve of LREE enrichment and negative anomaly of Eu, which shows alternation and metamorphism have strongly reconstructed the plagioclase of the original rock, and Ce is generally weak negative anomaly. （La/Sm）>1, and the rock has the characteristics of mid-ocean ridge T-type basalt. The gross amount of REE is relatively small and LREE is obviously rich in the rocks, which belong to the LREE enrichment type.4. The minerogenetic temperature, the matter source, the ore-forming fluids and the minerogenetic epoch of Dahongshan type iron-copper deposit have been systematically studied. The uniform temperature of inclusions is between 102℃and 370℃, which shows there exist two stages of mineralization: the early minerogenetic stage has 290-330℃uniform temperature, 16-32wt% salinity, the pH value of 3.7-3.0, logfs₂-70.2, logfo₂-26.55 and logfco₂ 3.3-1.5; while the late minerogenetic stage has 160-250℃uniform temperature 13.8-45wt% salinity, the pH value of 4.5-3.4, logfs₂-11.04, logfo₂-34.37 and logfco₂ 4.63-3.9. This shows the formation temperature is evolved from intermediate temperature（290-330℃） to intermediate-low temperature with the stage going from early to late. The isotope analysis of lead reveals that the mixed lead is originated from different sources, environments and stages. The isotope analysis of sulfur shows that the sulfur is originated from the reduction of sulfate of the sea water and part of which is originated from mantle sulfur carried up from deep part by volcanic eruption. That is to say, the sulfur is originated from the sulfur formed in volcanic activities mixed with that reduced from sea water; Judged from the value of d ¹⁸O_H2O and dD_H2O, the origin of the minerogenetic liquid （i.e. water） is relatively complex, and the media water of the minerogenetic period of the volcanic sedimentary is mainly originated from original magmatic water. Affected by sea water to a certain extent, during the reconstruction of late regional metamorphism, the minerogenetic liquid gradually evolved into minerogenetic fluid of magmatic water, metamorphic water combined with atmospheric condensation water. The chronological studies of isotopes shows that the age of K/Ar isotopes is mainly near 800Ma±20 Ma and this reveals the late alteration and reconstruction events of copper and iron mineral deposit of Dahongshan type and represents the era when volcanism, metamorphism and mineralization of uranium happened during Jinningian period. And the age is also the reconstruction age of Dahongshan ore deposit.5. The metallogenic series theory is applied to guide the prediction of ore finding. The 5 ore-controlled factors and 8 minerogenetic prediction signs of ore finding in the Dahongshan group is summarized according to the distribution regularity of the ore deposit in space expatiated by the metallogenic series and the regularity of evolution in epoch, which establishes the theory base on comprehensive information minerogenetic prediction.6. The geological, geophysical-geochemical characteristics of Dahongshan type iron-copper ore deposit are mainly researched on and the minerogenetic model for this ore deposit is established. Multivariate minerogenetic information theory is applied to discuss the overall geological characteristics in the researched area, including minerogenetic geological background, geochemistry, geophysics and remote sensing, and the geophysical and geochemical exploration models of ore finding and exploration at the Dahongshan type copper-iron ore deposits in the researched area are generally summed up. This paper also uses GIS-based multivariate physiographical minerogenetic information to carry out target area locating prediction for Dahongshan and Kunyang group in early Proterozoic. Finally, the research points out the prospect area of ore-finding and indicates the orientation for the ore-finding exploration of mines.更多还原