發(fā)布時(shí)間：2018-02-04 12:26

  本文關(guān)鍵詞： 義敦島弧 晚三疊世 斑巖銅礦 成礦作用　出處：《中國(guó)地質(zhì)大學(xué)(北京)》2017年博士論文　論文類(lèi)型：學(xué)位論文

【摘要】：義敦島弧形成于晚三疊世甘孜-理塘洋板塊向西俯沖過(guò)程中,其南部中甸(香格里拉)弧發(fā)育大量斑巖(矽卡巖)型礦床,區(qū)內(nèi)普朗斑巖型銅礦床為全球少有的具還原性特征的超大型斑巖型銅礦床,其規(guī)模遠(yuǎn)大于區(qū)內(nèi)其他“氧化性”礦床,與傳統(tǒng)斑巖成礦系統(tǒng)的一般認(rèn)識(shí)相悖。其原因是成礦母巖漿的來(lái)源或巖漿-流體出溶作用不同,還是成礦流體演化過(guò)程與金屬沉淀機(jī)制的差異?是研究區(qū)斑巖成礦作用的關(guān)鍵科學(xué)問(wèn)題。為此,本文從中甸弧內(nèi)主要斑巖(矽卡巖)型礦床的成礦斑巖體的巖石地球化學(xué)、同位素地球化學(xué)、成礦流體演化、流體包裹體均一溫度以及氫氧同位素等方面開(kāi)展系統(tǒng)研究,取得認(rèn)識(shí)如下:(1)巖體鋯石U-Pb年代學(xué)研究表明,東斑巖帶(普朗等)石英閃長(zhǎng)玢巖加權(quán)平均值為223±3.7 Ma,石英二長(zhǎng)斑巖為218±4 Ma,花崗斑巖為207±3.9 Ma。而西斑巖帶(雪雞坪等)的石英閃長(zhǎng)玢巖為234±8 Ma。石英二長(zhǎng)斑巖為219±2.6Ma�；◢彴邘r為218±1.8 Ma。即,存在西斑巖帶有略早于東斑巖帶的趨勢(shì)。晚三疊世甘孜-理塘洋向西俯沖,西帶屬于俯沖前端,其板片脫水熔融,經(jīng)MASH和AFC過(guò)程,形成早于東帶(后端)的巖體。(2)鋯石Hf-O同位素研究表明,石英閃長(zhǎng)玢巖的Hf(t)值偏負(fù)(普朗:-13.5到-8.9,雪雞坪:0.4-2.4),δ18O(‰)值偏高(普朗:5.74-6.9,平均6.11±0.16;雪雞坪:5.86-6.27,平均6.02±0.11),而石英二長(zhǎng)斑巖的Hf(t)值偏正(普朗:-3.8到2.74;雪雞坪:0.4到2.2),δ18O(‰)值偏低(普朗:4.95-6.17,平均5.75±0.13;雪雞坪:5.53-6.42,平均5.69±0.12),花崗斑巖和石英二長(zhǎng)斑巖相似。表明石英閃長(zhǎng)玢巖來(lái)源為相對(duì)較多的殼源物質(zhì),而石英二長(zhǎng)斑巖和花崗斑巖則幔源物質(zhì)增加,指示后者具有更富的成礦物質(zhì)來(lái)源。(3)石英閃長(zhǎng)玢巖巖漿氧逸度(Ce4+/Ce3+比值)相對(duì)較低(普朗:0.6-13.9,平均為4;雪雞坪:9.7-142.8,平均74.7),石英二長(zhǎng)斑巖巖漿氧逸度較高(普朗:5.4-99.6,平均52.1;雪雞坪:15.5-533.1,平均163.7),花崗斑巖和石英二長(zhǎng)斑巖相似。表現(xiàn)后者更具成礦潛力,這與地質(zhì)事實(shí)相符。(4)普朗礦床成礦流體演化后期有大氣降水的加入,引起流體不混溶。大氣降水有效萃取、攜帶圍巖地層中有機(jī)質(zhì),較好的還原條件,導(dǎo)致成礦物質(zhì)有效地沉淀成礦。而雪雞坪等礦床沒(méi)有還原性成分的加入,從而難以形成普朗式的超大型斑巖礦床。
[Abstract]:The Yidun island arc was formed during the westward subduction of the Ganzi-Litang ocean plate in the late Triassic, and a large number of porphyry (skarn) deposits were developed in the southern Zhongdian (Shangri-La) arc. The Plang porphyry copper deposit is one of the rare super-large porphyry copper deposits with reductive characteristics in the world, and its scale is much larger than that of other "oxidizing" copper deposits in the region. It is contrary to the general understanding of the traditional porphyry ore-forming system because of the origin of the ore-forming parent magma or the dissolution of magmatic fluid or the difference between the evolution process of ore-forming fluid and the mechanism of metal precipitation. It is a key scientific problem of porphyry metallogeny in the study area. In this paper, the geochemistry, isotopic geochemistry and ore-forming fluid evolution of the ore-forming porphyry bodies of the main porphyry (skarn) deposits in Zhongdian arc are studied. A systematic study on homogenization temperature of fluid inclusions and hydrogen and oxygen isotopes has been carried out. The results are as follows: (1) zircon U-Pb geochronology of the pluton shows that, The weighted average value of quartz diorite porphyrite in the East porphyry Zone (Plang et al.) is 223 鹵3.7 Ma., the quartz monzodiorite porphyry is 218 鹵4 Ma., the granitic porphyry is 207 鹵3.9 Ma.The quartz diorite porphyrite in the West porphyry Zone (Xuejiiping et al) is 234 鹵8 Ma. the quartz diorite porphyry is 219 鹵2.6 Ma.The granitic porphyry is 218 鹵1.8 Ma. There is a tendency that the western porphyry is a little earlier than the eastern porphyry belt. The late Triassic Ganzi-Litang ocean subducted westward, and the western belt belongs to the front of the subduction, and its plate is dehydrated and melted through MASH and AFC process. The Hf-O isotopic study of zircon formed earlier than the back end of the east belt shows that, In quartz diorite porphyrite, the values are negative (Prang: -13.5 to -8.9, Xue Chicken Ping: 0.4-2.4, 未 18O (鈥，

本文編號(hào)：1490205