本文關(guān)鍵詞： 氧逸度 富堿斑巖 鋯石 北衙金礦 滇西　出處：《中國(guó)地質(zhì)大學(xué)(北京)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：斑巖型礦床是世界上銅、鉬的主要來(lái)源,很多斑巖型銅礦富含金,可構(gòu)成超大型金礦,也是金的重要來(lái)源。世界上許多的超大型-大型斑巖礦床的產(chǎn)出環(huán)境往往與與板塊俯沖有關(guān),主要包括島弧和陸緣弧環(huán)境。近年的研究工作發(fā)現(xiàn)在陸內(nèi)環(huán)境、后碰撞環(huán)境中,也發(fā)育一系列大型-超大型斑巖礦床。這些斑巖礦床與弧環(huán)境產(chǎn)出的斑巖礦床有著較多相似之處,但其成巖成礦的年齡均與后碰撞和碰撞構(gòu)造背景密切相關(guān),而與弧環(huán)境以及洋殼俯沖沒(méi)有直接的關(guān)系。相對(duì)而言,產(chǎn)于弧環(huán)境中的斑巖型礦床的巖漿氧逸度較高,而對(duì)于后碰撞陸內(nèi)環(huán)境斑巖礦床巖漿氧逸度及其成礦制約尚缺乏系統(tǒng)論述。滇西北衙礦集區(qū)位于印度-歐亞大陸碰撞后形成的陸內(nèi)環(huán)境,是該區(qū)域規(guī)模最大的金多金屬礦床,斑巖體在礦區(qū)呈巖株?duì)顝V泛出露,但除了在萬(wàn)硐山、紅泥塘、馬頭灣、南大坪等幾個(gè)斑巖體中先后發(fā)現(xiàn)金礦體,周圍很多斑巖體并無(wú)礦化。對(duì)于斑巖型礦床的含礦與無(wú)礦斑巖體,它們之間的差別一直備受關(guān)注。論文通過(guò)巖相學(xué)和巖石地球化學(xué)特征,對(duì)比分析了北衙礦區(qū)發(fā)育的富堿斑巖巖相學(xué)、地球化學(xué)特征、鋯石微量元素特征以及巖漿氧逸度的差異,探討了巖漿氧逸度對(duì)成礦的制約。取得的主要認(rèn)識(shí)如下:1、鋯石LA-ICP-MS測(cè)年顯示,北衙礦集區(qū)的含礦巖體與無(wú)礦巖體的年齡接近,集中在36 Ma左右。2、通過(guò)鋯石微量元素對(duì)各個(gè)巖體進(jìn)行對(duì)比研究,北衙金礦床的含礦巖體的鋯石Ce~(4+)/Ce~(3+)比值普遍高于無(wú)礦巖體,并且含礦巖體的巖漿氧逸度也普遍高于無(wú)礦巖體。3、北衙金礦床富堿斑巖有著與埃達(dá)克巖相似的地球化學(xué)特征,其源區(qū)為加厚下地殼,含礦巖體的源區(qū)可能受到富集地幔物質(zhì)的影響,使其具有不同的特征。富集地幔經(jīng)歷過(guò)洋殼的俯沖改造,有著高的S含量和高的氧逸度,在較高的氧逸度條件下,S以SO_4~(2-)的形式在巖漿中高度富集,使得親銅元素Cu、Au不斷富集,為該區(qū)的斑巖型Cu-Au礦化提供了成礦物質(zhì)來(lái)源。
[Abstract]:Porphyry deposits are the main source of copper and molybdenum in the world. Many porphyry copper deposits are rich in gold and can form super-large gold deposits. It is also an important source of gold. The occurrence environment of many super-large porphyry deposits in the world is often related to plate subduction, including island arc and continental margin arc environment. A series of large and super-large porphyry deposits are also developed. These porphyry deposits are similar to porphyry deposits in arc environment, but their diagenetic and metallogenic ages are closely related to the post-collision and collisional tectonic setting. In contrast, porphyry deposits occurring in arc environments have higher oxygen fugacity of magma. However, the oxygen fugacity of magma and its ore-forming constraints in post-collision continental environment porphyry deposits are not discussed systematically. The Ya ore concentration area in northwest Yunnan is located in the intracontinental environment formed after the India-Eurasia collision, and is the largest gold polymetallic deposit in this region. The porphyry is widely exposed in the mining area, but gold ore bodies have been discovered in Wandong Mountain, Hongjitang, Matou Bay, Nandaping and other porphyry bodies. Many porphyry bodies are not mineralized. The differences between ore-bearing and ore-free porphyry bodies in porphyry deposits have been paid close attention to. The differences in lithology, geochemistry, trace element characteristics of zircon and oxygen fugacity of magma developed in Beiya mining area are compared and analyzed. The constraints of magmatic oxygen fugacity on mineralization are discussed. The main conclusions are as follows: 1. Zircon LA-ICP-MS dating shows that the age of ore-bearing rock mass in Beiya ore concentration area is close to that of ore-free rock mass. Concentrated at 36 Ma or so, the zircon trace elements were used to study each rock mass. The results show that the ratio of zircon Ce~(4 / CEO _ 3 in the ore-bearing rock body of Beiya gold deposit is generally higher than that of the ore-free rock mass. The oxygen fugacity of magma of ore-bearing rock is generally higher than that of ore-free rock. The alkali-rich porphyry of Beiya gold deposit is similar to that of adakite, and its source area is thickened lower crust. The source region of the ore-bearing rock may be affected by the enriched mantle material, which has different characteristics. The enriched mantle has undergone subduction transformation of the oceanic crust, with high S content and high oxygen fugacity. Under the condition of high oxygen fugacity, S is highly enriched in magma in the form of so _ 4C _ 4 ~ (2), which leads to the continuous enrichment of Cu _ 2O _ (-au), which provides a source of ore-forming material for porphyry type Cu-Au mineralization in this area.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P618.51

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