發(fā)布時間：2018-05-02 18:35

  本文選題：巖石地球化學(xué) + U-Pb年代學(xué)與Hf同位素　； 參考：《中國地質(zhì)大學(xué)(北京)》2016年博士論文

【摘要】：本文圍繞碧口地體構(gòu)造演化與區(qū)域成礦作用關(guān)系,通過對碧口地體與鄰區(qū)出露的巖石建造以及不同類型礦床(新太古代BIF型鐵礦床、新元古代VMS型銅多金屬礦床、泥盆紀沉積型硅礦床、三疊紀造山型金礦床)開展了詳細的野外地質(zhì)觀測、巖石地球化學(xué)分析、成巖成礦年代學(xué)、鋯石Lu-Hf同位素、金屬礦物電子探針與原位LA-ICP-MS分析,獲得以下主要認識。(1)新太古代魚洞子群與侵入其中的花崗巖構(gòu)成了碧口地體新太古代陸核。魚洞子群海相火山-沉積巖系在~2.6 Ga遭受了區(qū)域變質(zhì)作用,并形成了以條帶狀鐵建造(BIF)為賦礦圍巖的BIF型鐵礦床。結(jié)合礦床地質(zhì)特征、磁鐵礦電子探針和原位LA-ICP-MS分析,明確魚洞子鐵礦床為BIF型鐵礦床。(2)新元古代為碧口地體地殼增生期,洋陸俯沖背景下的弧前盆地濁積巖、弧后裂谷盆地與陸緣弧火山巖、侵入巖構(gòu)成了碧口地體主體。雙峰式火山巖與該區(qū)VMS礦床成因關(guān)系密切。別子型VMS銅礦床產(chǎn)于基性火山巖(細碧巖)中,黑礦型VMS礦床產(chǎn)于中性-中酸性火山巖(角斑巖-石英角斑巖)中。黃銅礦原位LA-ICP-MS分析顯示黑礦型比別子型含更多Pb、Bi和Ag,且黃鐵礦Co/Ni1。(3)古生代碧口地體北緣處于陸緣裂陷構(gòu)造背景。勉略構(gòu)造帶內(nèi)硅質(zhì)巖的巖石學(xué)、地球化學(xué)、碎屑鋯石U-Pb年代學(xué)及Hf同位素表明,大量來自華南板塊(尤其碧口地體)的新元古代巖漿巖與沉積巖碎屑向北運移至陸緣裂陷,并與來自裂陷深部的富硅流體一起沉淀下來,在勉略構(gòu)造帶內(nèi)形成了該區(qū)不同時代的硅質(zhì)巖,這些不同時代硅質(zhì)巖反映碧口地體北緣的裂陷作用東部早于西部。此外,這些硅質(zhì)巖巖層具經(jīng)濟價值,構(gòu)成了沉積型硅礦床。(4)印支期隨著中國華南、華北板塊的碰撞拼合,該區(qū)隨即進入陸內(nèi)造山階段,構(gòu)造體制由南北向的擠壓碰撞轉(zhuǎn)為應(yīng)力松弛,表現(xiàn)為區(qū)域性的左行剪切走滑。在這種構(gòu)造背景下,該區(qū)形成了后碰撞板片斷離花崗巖。并在勉略構(gòu)造帶內(nèi)形成了以變質(zhì)流體作為成礦流體來源的不同深度造山型金礦床,如文縣陽山淺成造山型金礦床和略陽鏵廠溝中淺成造山型金礦床等。
[Abstract]:Based on the relationship between the tectonic evolution of the Bikou terrane and regional metallogenesis, the rock formations and different types of deposits (NeoArchean BIF iron ore deposit, Neoproterozoic VMS type copper polymetallic deposit) in the Bikou terrane and adjacent areas are studied in this paper. Devonian sedimentary silicon deposits and Triassic orogenic gold deposits) have been developed for detailed field geological observation, petrogeochemical analysis, diagenetic geochronology, zircon Lu-Hf isotopes, electron probe analysis of metallic minerals and in situ LA-ICP-MS analysis. The main understanding is as follows. 1) the NeoArchean fishhole subgroup and the intrusive granite formed the NeoArchean continental nucleus of the Bikou terrane. The marine volcanic-sedimentary rock series of the Yudong subgroup suffered from regional metamorphism at 2.6Ga and formed a BIF type iron deposit with banded iron formations as host rocks. Combined with the geological characteristics of the deposit, electron probe analysis of magnetite and in situ LA-ICP-MS analysis, it is clear that the Yudongzi iron deposit is a BIF type iron deposit.) the Neoproterozoic is the turbidite of the Pikou terrane during the crustal accretion period and the oceanic subduction setting. Back-arc rift basin and continental margin arc volcanic rocks, intrusive rocks constitute the main body of Bikou terrane. Bimodal volcanic rocks are closely related to the genesis of VMS deposits in this area. The peer-type VMS copper deposit occurs in the basic volcanic rocks and the black type VMS deposits occur in the neutral and intermediate acid volcanic rocks (hornblene-quartz keratophytes). The in-situ LA-ICP-MS analysis of chalcopyrite shows that the black ore type contains more PBO Bi and Ag than the subtype, and the Paleozoic Bikou terrane north margin is located in the continental margin rifting tectonic setting. The petrology, geochemistry, U-Pb chronology of clastic zircon and HF isotopes of siliceous rocks in the Mianliao tectonic belt indicate that a large number of Neoproterozoic magmatic and sedimentary rocks from the South China plate (especially the Bikou terrane) migrated northward to the continental margin rift. Together with silicon-rich fluids from deep rifting, siliceous rocks of different ages were formed in the Mianliao structural belt, which reflected that the rifting in the northern margin of the Bikou terrane was earlier than that in the west. In addition, these siliceous rock formations are of economic value and form sedimentary silicon deposits. The Indosinian epoch followed the collision and assembly of the South China and North China plates, and the area immediately entered the intracontinental orogenic stage. The tectonic system changed from the compression collision in the south to north direction to the stress relaxation, which is characterized by regional left shear strike-slip. In this tectonic setting, the post-collision plate fragment is formed in this area. Different depth orogenic gold deposits with metamorphic fluids as the source of ore-forming fluids have been formed in the Mianliao structural belt, such as the metamorphic fluids in Wenxian County, Yangshan superficial orogenic type gold deposits and Lueyang Huachanggou medium and superficial orogenic gold deposits, etc.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P612
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本文編號：1835022