發(fā)布時間：2018-02-10 15:07

  本文關(guān)鍵詞： 岡底斯 早白堊世巖漿作用 巖石成因 地球化學(xué) 成礦意義　出處：《地質(zhì)學(xué)報(bào)》2017年04期 　論文類型：期刊論文

【摘要】：西藏岡底斯中部廣泛發(fā)育中新生代巖漿活動,而其巖石成因及巖漿源區(qū)仍存爭議。早白堊世巖漿作用既是探究岡底斯帶大規(guī)模的巖漿成礦作用的關(guān)鍵要素,又是認(rèn)識其地球動力學(xué)過程的關(guān)鍵窗口。本文以中岡底斯帶確角弄地區(qū)出露的早白堊世花崗質(zhì)巖體為對象,進(jìn)行了詳細(xì)的LA-ICP-MS鋯石U-Pb年代學(xué)、全巖地球化學(xué)和Sr-Nd同位素研究�；◢徺|(zhì)巖體巖石類型以黑云母花崗閃長巖為主,其次為石英二長巖、正長花崗巖等,屬I型偏鋁質(zhì)高鉀鈣堿性系列花崗巖。確角弄巖體黑云母花崗閃長巖侵位年齡為127±1.6Ma,(~(87)Sr/~(86)Sr)_i值高(0.70926~0.71424),負(fù)全巖ε_(Nd)(t)值(-7.0~-9.1),微量元素表現(xiàn)出消減帶富集大離子親石元素、虧損高場強(qiáng)元素的特征,顯示島弧花崗巖的親緣性。巖漿源區(qū)主要來自古老基底巖石的部分重熔并可能有少量幔源物質(zhì)的參與,經(jīng)歷了強(qiáng)烈分離結(jié)晶作用。巖石成因可能與早白堊世時受到班公湖-怒江洋殼巖石圈向南俯沖過程中發(fā)生的板片斷離有關(guān)。確角弄巖體是中岡底斯早白堊世帶狀巖漿大爆發(fā)事件在中部的延續(xù)。巖體與圍巖接觸帶發(fā)生了強(qiáng)烈的熱液蝕變,具有很高的鐵鎢物化探異常值,局部地方發(fā)現(xiàn)了磁鐵礦礦化點(diǎn),成礦巖體鋯石都具較高的Ce~(4+)/Ce~(3+)比值(450~769),鋯石Ti飽和溫度較高為776℃左右,顯示成礦巖漿為高溫巖漿熱液體系并具有高氧逸度特征,化探趨勢剩余異常的空間展布受地層巖性、斷裂構(gòu)造、巖漿巖控制明顯,指示了良好的鐵鎢找礦前景。
[Abstract]:The Meso-Cenozoic magmatic activity is widely developed in the central Gangdis, Tibet, and its petrogenesis and magmatic source are still disputed. The early Cretaceous magmatism is the key element in exploring the large-scale magmatic mineralization in the Gangdese belt. In this paper, the early Cretaceous granitic granitic bodies in the Qiaojiaonong area of the Middle Gangdis belt are taken as the objects, and the LA-ICP-MS zircon U-Pb geochronology is carried out in detail. The main rock types of granitic bodies are biotite granodiorite, followed by quartz monzonite, syenite, etc. It belongs to type I metamorphic high-potassium calc-alkaline granitoids. The emplacement age of biotite granodiorite is 127 鹵1.6 Ma-1. The age of biotite granodiorite is 127 鹵1.6 Ma. The age of biotite granodiorite is 127 鹵1.6 Ma. The Sr / P ~ (86) T ~ (-1) value is 0.70926 ~ (0.71424), and the negative whole rock 蔚 ~ (-1) is -7.0 ~ (-1) ~ (-1) ~ (-1) ~ (-1). The trace elements are characterized by the enrichment of large ion lithophile elements in subduction zone and the depletion of high field strength elements. The magmatic source mainly comes from the partial remelting of the ancient basement rocks and may involve a small amount of mantle material. The genesis of the rocks may be related to the plate fragments that occurred during the southward subduction of the Bangonghu-Nujiang oceanic lithosphere during the early Cretaceous. The Keijiaonong rock body is a belt of the Middle Cretaceous early Cretaceous. The magmatic eruption continued in the central part of the country. A strong hydrothermal alteration occurred in the contact zone between the rock mass and the surrounding rock. It has a very high anomalous value of ferro-tungsten geophysical and geochemical prospecting. Magnetite mineralization points have been found locally. The zircon of the ore-forming rock mass has a high Ce~(4 / ce ~ (3) ratio of 450 ~ 769 ~ (9), and the Ti saturation temperature of zircon is about 776 鈩，

本文編號：1500799