【摘要】：西藏雄村銅金礦區(qū)位于岡底斯造山帶中段南緣,其南緊鄰雅魯藏布縫合帶(IYS)和日喀則弧前盆地,北為謝通門(mén)始新世大巖基。目前礦區(qū)主要由I、II、III號(hào)主礦體及相關(guān)礦化體組成,共探獲I、II號(hào)礦體331+332+333類別銅金量230多萬(wàn)噸、金金屬量210多噸、銀金屬量1000多噸,III號(hào)礦體預(yù)期銅金屬量超過(guò)30萬(wàn)噸,且其他礦化體如洞噶金礦等也具有良好的找礦前景。礦床形成于早-中侏羅世,為與新特提斯洋洋殼俯沖作用形成的石英閃長(zhǎng)玢巖有關(guān)的斑巖型礦床,查明礦床形成的大地構(gòu)造背景對(duì)區(qū)域找礦方向具有重要指示意義,同時(shí)也為區(qū)域構(gòu)造演化提供參考。本文通過(guò)對(duì)產(chǎn)于雄村組火山巖沉積巖中的砂巖進(jìn)行研究,對(duì)砂巖采用主量、微量元素分析、鋯石U-Pb年代學(xué)及鏡下鑒定等研究工作,揭示雄村組砂巖的物源屬性及物源區(qū)的大地構(gòu)造背景,取得了如下認(rèn)識(shí):(1)鏡下鑒定和A-CN-K圖解表明雄村砂巖經(jīng)歷了較強(qiáng)的粘土化作用,但并不影響其對(duì)構(gòu)造背景和物源的判別,碎屑含量大于80%,可見(jiàn)較多火山巖巖屑和長(zhǎng)石碎屑,多發(fā)生粘土化,部分保留長(zhǎng)石晶型假象,為長(zhǎng)石巖屑砂巖。局部可見(jiàn)砂巖常具有粒序?qū)永砗皖愃颇ダ逊e特征,為活動(dòng)的大洋火山島弧所致。(2)雄村組砂巖中鋯石基本為巖漿成因鋯石,多具有清晰的振蕩環(huán)帶,且搬運(yùn)距離不遠(yuǎn)。兩個(gè)砂巖樣品碎屑鋯石年齡組成(205Ma~190Ma)說(shuō)明雄村組砂巖物源主要為早侏羅世火山-侵入巖。(3)雄村砂巖的主量元素、微量元素及稀土元素特征與大洋島弧環(huán)境相近,結(jié)合La-Th-Sc、Th-Sc-Zr/10、Th-Co-Zr/10和La/SC-Ti/Zr圖解投圖結(jié)果,確定雄村砂巖構(gòu)造環(huán)境為大洋島弧環(huán)境。(4)物源判別Co/Th-La/Sc和La/Th-Hf圖解表明雄村砂巖物源區(qū)為長(zhǎng)英質(zhì)中-酸性火山巖和安山質(zhì)火山巖,A-CN-K圖解同樣顯示出砂巖成分與安山質(zhì)、英安質(zhì)火山巖相同。其次,雄村砂巖主量元素和微量元素特征與該區(qū)域火山巖特征相似,指示物源與雄村火山巖-侵入巖有關(guān)。所以雄村砂巖物源區(qū)為中-酸性安山質(zhì)、英安質(zhì)大洋島弧火山巖,而非陸緣弧的產(chǎn)物。(5)雄村組砂巖形成晚于或近于雄村銅金礦床的成巖成礦年齡,砂巖地球化學(xué)特征及礦區(qū)內(nèi)砂巖與成礦巖體的空間關(guān)系表明雄村火山巖就是雄村砂巖的物源,所以雄村銅金礦床形成于大洋島弧環(huán)境而非陸緣弧環(huán)境,其賦礦圍巖是一套產(chǎn)于洋內(nèi)島弧背景下的中-酸性火山巖夾火山沉積巖。(6)雄村島弧型斑巖型礦床的識(shí)別對(duì)于找礦勘查具有兩個(gè)重要的指示:一是從斑巖型礦床成群、成帶分布的規(guī)律來(lái)看,在南木林-謝通門(mén)雅魯藏布江北岸分布的大量侏羅紀(jì)巖體應(yīng)該同樣具有形成大洋島弧有關(guān)礦床的成礦潛力;二是在雄村礦區(qū)的更北部應(yīng)該存在與新特提斯洋俯沖有關(guān)的陸緣火山弧,同樣具有形成產(chǎn)于陸緣弧背景下的斑巖型、矽卡巖型礦床。
[Abstract]:Xiongcun copper and gold deposit area in Tibet is located in the southern margin of the Gangdis orogenic belt, adjacent to the Yalu Zangbo suture zone (IYS) and Xigaze forearc basin, and to the north is the large Eocene rock base of Xetongmen. At present, the ore area is mainly composed of the main ore body of Izao II No. III and its related orebodies. A total of more than 2.3 million tons of copper and gold, more than 210 tons of gold and 1000 tons of silver of the No.3 ore body are found to have an expected copper and gold content of more than 300000 tons. Other orebodies, such as Dongga gold deposit, also have good prospecting prospects. The deposit was formed in the early and Middle Jurassic. It is a porphyry type deposit related to the new Tethys oceanic crust subduction. It is found that the tectonic setting of the deposit formation is of great significance to the direction of regional prospecting. It also provides a reference for regional tectonic evolution. In this paper, the sandstone occurring in the volcanic sedimentary rocks of Xiongcun formation is studied, and the main quantity, trace element analysis, zircon U-Pb geochronology and microscopic identification of sandstone are used. By revealing the provenance attribute of Xiongcun formation sandstone and the tectonic background of the source area, the following conclusions have been obtained: (1) the identification and A-CN-K diagram show that Xiongcun sandstone has experienced strong clayization, but it does not affect the discrimination of tectonic background and provenance. The content of clastic rocks is more than 80. More volcanic and feldspar clastic rocks can be seen. Most of them are clay-forming, and some of them retain the false appearance of feldspar crystal type, which is feldspar lithic sandstone. Locally visible sandstone is usually characterized by grain sequence stratification and similar to morlite accumulation, which is caused by active oceanic volcanic island arc. (2) in Xiongcun formation, zircon is basically magmatic zircon, most of them have clear oscillatory ring zone, and the transport distance is not far. The zircon age composition of two sandstone samples (205Ma-190Ma) indicates that the sandstones of Xiongcun formation mainly originated from early Jurassic volcanic-intrusive rocks. (3) the main elements, trace elements and rare earth elements of Xiongcun sandstone are similar to those of the oceanic island arc environment. Combined with La-Th-Sctr Th-Sc-Zr10 / 10 Th-Co-Zr / 10 and La / SC-Ti / Zr diagram, It is determined that the tectonic environment of Xiongcun sandstone is oceanic island arc environment. (4) the source identification of Co-Th-La-Sc and La-Th-Hf shows that the source areas of Xiongcun sandstone are felsic intermediate-acid volcanic rocks and anshanian volcanic rocks. Anglo-volcanic rocks are the same. Secondly, the main elements and trace elements of Xiongcun sandstone are similar to that of volcanic rocks in this area, and the indicator source is related to Xiongcun volcanic rocks and intrusive rocks. Therefore, the source area of Xiongcun sandstone is intermediate-acid anshan, Yingan oceanic island arc volcanic rock, rather than the product of continental margin arc. (5) the sandstone of Xiongcun formation was formed later than or near the diagenetic age of Xiongcun copper-gold deposit. The geochemical characteristics of sandstone and the spatial relationship between sandstone and ore-forming rock mass indicate that Xiongcun volcanic rock is the source of Xiongcun sandstone, so Xiongcun copper-gold deposit was formed in the oceanic island arc environment rather than the continental margin arc environment. The ore-bearing surrounding rock is a set of intermediate-acid volcanic rocks intercalated with volcanic sedimentary rocks under the background of Yu Yang inner island arc. (6) the identification of Xiongcun island arc porphyry deposits has two important indications for prospecting and exploration: first, the formation of porphyry deposits from porphyry deposits. From the rule of zonal distribution, a large number of Jurassic rock bodies distributed in the northern bank of the Nammulin-Xetongmen Yalu Zangbo River should have the same metallogenic potential to form oceanic island arc related deposits. Second, there should be continental margin volcanic arcs related to the new Tethys ocean subduction in the north of Xiongcun mining area, which also has porphyry type and skarn type deposit formed in the background of continental margin arc.
【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P618.41;P618.51

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