金沙江-红河新生代富碱岩浆挥发性组分特征及其对成矿的制约

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	金沙江-红河新生代富碱岩浆挥发性组分特征及其对成矿的制约
	王蝶
导师	毕献武
	2013
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位名称	博士
学位专业	矿物学、岩石学、矿床学
关键词	挥发性组份流体包裹体硅酸盐熔融包裹体金沙江-红河富碱侵入岩带
摘要	对岩浆中挥发性组分(H2O，CO2，F，C1，B，S等)及其性状的研究，已成为花岗岩成岩、成矿研究领域十分重要的一环。近年来许多与富碱侵入岩有关的大型-超大型铜、金矿床的发现，使得原本被认为贫水而难以分异流体成矿的富碱侵入岩受到了国内外学者的极大关注。研究表明，与成矿有关的富碱侵入岩具有富水等挥发性组分的特征，大洋板片脱水对富水等挥发性组分含矿岩浆的形成发挥了关键作用。富碱侵入岩主要产于两大构造环境：一是汇聚板块边缘的岛弧和大陆弧环境，二是大陆内部环境。近二十几年来，一些学者较系统地总结和研究了岛弧及大陆弧环境与金、铜成矿有关的（富碱）岩浆系统的形成演化过程，认为与富碱弧岩浆有关的Cu和Au矿床是大洋板块俯冲诱导的高fO2富水等挥发性组分岩浆活动的产物。但是针对大陆内部富碱岩浆系统相关的研究则十分薄弱，从而制约了对大陆富碱岩浆系统成矿机制和成矿规律的深入认识。金沙江—红河新生代富碱侵入岩带产出众多与富碱岩浆有关的斑岩型Cu、Au矿床，是世界上大陆内部环境富碱岩浆成矿作用的典型区域。本文通过对金沙江—红河新生代富碱侵入岩带内的含矿与不含矿岩体的矿物化学、微量元素地球化学、流体包裹体地球化学以及稳定同位素地球化学等方面的研究，探讨了富碱侵入岩的挥发性组分特征及其对成矿的可能的制约机制。取得主要认识包括： 1. 1. 带内的富碱斑岩总体上SiO2含量在60～70%之间，属于中酸性岩石，具有高碱富K、富F、富CO2而贫Cl、贫H2O的特点，与弧环境斑岩富Cl、富H2O、低F、贫CO2的性质具有较大差别，是大陆内部成岩成矿背景特殊性的体现。造成两种构造背景形成的岩浆中挥发性组成的差异主要是二者岩浆形成源区的差异性所致。而导致源区差异的原因主要是俯冲进入岩浆源区的沉积物质的差异，弧环境的玄武岩洋壳、深海硅质岩沉积等以富含Na、Cl、H2O为特征；大陆内部环境以克拉通、浅海盆地碳酸盐、含F、K碎屑岩沉积物质为主。2. 含矿与不含矿富碱斑岩含水等挥发性组分特征存在明显差异，相对于不含矿富碱斑岩，含矿富碱斑岩明显富集水等挥发性组分。主要表现在： 1）岩石矿物组合上存在较大的差异：与矿有关的岩体普遍发育含水矿物黑云母、角闪石和磷灰石，而无矿岩体黑云母和角闪石含量普遍较低甚至不发育角闪石和黑云母；2）与Cu成矿有关岩体中的角闪石、黑云母主要是浅闪石和镁黑云母、金云母，具有高Mg含量的特点；与Au成矿有关岩体中的角闪石、黑云母主要是含铁质韭闪石、镁黑云母和铁质云母，具有高Fe的特点。显示出不同种类矿床中暗色矿物种属的成矿专属性。含水矿物磷灰石、黑云母和角闪石探针数据都显示，与金成矿有关的岩体具有Cl高F低的特点，与铜成矿有关岩体Cl稍低而F稍高，不含矿岩体则具有F高Cl低的特点，整体上说明含矿岩体中的络合离子元素Cl比无矿岩体中高；3）包裹体岩相学研究表明，含矿岩体和无矿岩体斑晶矿物中的包裹体类型有较大的差异：不含矿岩体斑晶矿物中以发育原生岩浆熔融包裹体为主，很少或没有流体包裹体；而含矿岩体的斑晶矿物中则普遍发育流体包裹体，很少或几乎没有原生熔融包裹体。指示含矿岩体普遍受到流体改造，而不含矿岩体受到的流体改造较小或者几乎没有没到流体改造。说明在含水性上，含矿岩体比不含矿岩体有截然的优势。3. 含矿与不含矿富碱岩浆含水等挥发性组分特征存在差异的原因，很可能是这些岩浆的源区受到流体交代程度有所不同。
其他摘要	The study of the volatile components (H2O, CO2, F, C1, B, S, etc.) and their properties in the magma has been very important to the redearch of granitic rock and its metallogenesis. In recent years, the discovery of many ultra-large copper-gold deposits associated with alkaline-rich magma makes the alkaline-rich intrusive rock attracts great attention which was ignored before because of the character of absence of water, which is the key element for minerogenesis. Recent research shows that the alkaline-rich intrusive rocks associated with mineralization has the characteristic that enrich in volatile components, and oceanic slab dehydrated melting has played a key role in the formation of ore-bearing magma. There are two kinds of environment for the formation of alkaline-rich intrusive rocks, one is the island arc and the continental arc on the edge of convergent and the other is the continental tectonic setting. In the latest 20 years, scholars have summarized and studied the formation and evolution process of (alkaline-rich) magma system associated with Cu and Au metallogenesis in the island arc and continental arc environment. They thought that the Cu-Au deposits associated with alkaline-rich arc magmatic are the product of magmatic activity that has a character of high fO2 and enrichs in water content and other volatile components induced by oceanic plate subduction. But the study of intracontinental alkaline-rich magma system is very abcent. which limits the understanding of ore-forming mechanism and metallogenetic regularity of alkaline-rich magma system in continental tectonic setting. The Jinshajiang- Red-River alkaline-rich intrusive belt is a typical area of alkaline-rich magmatic mineralization in continental tectonic setting, and with many porphyry Cu-Au deposits associated with rich-alkaline intrusions. This paper carries out the study of the mineral chemistry, trace element geochemistry, fluid inclusion geochemistry and stable isotope geochemistry on the ore-bearing and barren rocks in Jingshajiang-Red-River alkaline-rich intrusive belt, and then discusses the characteristics of volatile components of alkaline-rich intrusive rocks and the potential restrictive mechanism to the mineralization. We get the following conclusions: 1. The SiO2 content of alkaline-rich intrusive rocks studied are between 58-70%, so that divided into intermediate-acid rock series and have the character of high alkaline and rich in K. They also have the characteristics of high content of F、CO2 and low Cl and H2O, which is distinct from the magma in the island arc and continental arc that enrich in Cl and H2O. 2. The character of volatile components in ore-bearing and ore-barren rocks is distinct, and the former are richer in volatile components such as water. Their difference is mainly manifested in the following three aspects: 1) The mineral assemblage of them has great differences: the rock associated with ore have more water-bearing minerals such as biotite, hornblende and apatite, which are less in the ore-barren rocks; 2) According to the results of component analysis of apatite, biotite and hornblende tested by electron probe, the content of F in alkaline-rich rocks are high but the content of Cl and OH are low. But the content of Cl and OH in the rocks associated with ore is higher than ore-barren rocks on average; 3) The type of inclusions in ore-bearing and ore-barren rocks are distinctly different. Silicate melt inclusions are dominated in minerals in ore-barren rocks, however the fluid inclusions are rare or non-existent; but opposite in ore minerals. It indicates ore-bearing rocks are metasomatized by fluid in a larger extent but ore-barren rocks are less or none metasomatized. 3. The cause of the distinction of volatile constituent between ore-bearing and barren rocks are likely due to the difference of fluid metasomatism in the magma source area.
学科领域	矿床地球化学
语种	英语
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/5808
专题	研究生_研究生_学位论文
推荐引用方式 GB/T 7714	王蝶. 金沙江-红河新生代富碱岩浆挥发性组分特征及其对成矿的制约[D]. 北京. 中国科学院研究生院,2013.

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