本文關(guān)鍵詞： 東天山 卡拉塔格 含礦地層 地球化學(xué) SIMS鋯石U-Pb年齡　出處：《中國地質(zhì)大學(xué)(北京)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：卡拉塔格位于東天山吐哈盆地南緣,屬于大南湖-頭蘇泉古生代增生島弧帶。區(qū)內(nèi)主要發(fā)育了VMS、斑巖-矽卡巖、次火山熱液型以及銅鎳硫化物等四類成礦系統(tǒng)。其中,VMS和次火山熱液型礦床主要賦存于古生代地層中,至下而上可分為三個(gè)巖性段。本文利用實(shí)測地質(zhì)剖面,系統(tǒng)采集火山巖樣品,開展巖石主微量、Sr-Nd同位素以及SIMS鋯石U-Pb同位素實(shí)驗(yàn)。對其地層特征有以下幾點(diǎn)創(chuàng)新性認(rèn)識:卡拉塔格核部早古生代晚期的含礦地層屬于大柳溝組。大柳溝組火山巖第一巖性段為海相中基性火山巖,其形成時(shí)代上限為晚奧陶世(450Ma),具中鉀鈣堿性-低鉀鈣堿性特征,富集LREE和Rb、Ba、U、K等大離子親石元素,以及Pb、Th、Zr、Hf元素,而虧損Nb、Ta以及元素P、Ti和Sr。大柳溝組火山巖第二巖性段為海相中性火山巖-火山碎屑巖,其形成時(shí)代上限為早志留世(440Ma),受海底熱液作用明顯,發(fā)生了強(qiáng)烈的黃鐵絹云母化、綠泥石化和硅化,有較強(qiáng)的蝕變分帶性。富集LREE和Rb、Ba、U、K等大離子親石元素,而虧損Nb、Ta以及元素P、Ti。大柳溝組火山巖第三巖性段為淺海相-陸相中酸性火山巖-火山碎屑巖,其形成時(shí)代上限為晚志留世-早泥盆世(420Ma),低鉀、富鈉、中基性較酸性富鈣,從中性火山巖到酸性火山巖,稀土總量隨著巖漿分異演化順序逐漸提高、Eu元素從無異常到明顯負(fù)異常,富集Rb、Ba、K等大離子親石元素,而虧損Nb、Ta、P、Ti、Sr等元素。大柳溝組整體上表現(xiàn)出典型的島弧巖漿的地球化學(xué)特征,第三巖性段明顯富鈉,而第一、第二巖性段的火山巖蝕變強(qiáng)烈,其Na2O含量降低。Sr-Nd同位素顯示火山巖(87Sr/86Sr)i介于0.704701~0.707351,εNd(t)介于2.12~7.44,侵入這套火山巖地層的中酸性巖漿巖(87Sr/86Sr)i介于0.703770~0.705203,εNd(t)介于5.66~6.84,表明其來源于虧損地幔,受到較弱的地殼物質(zhì)的混染,而受海水影響明顯。隨著卡拉麥里洋向南俯沖,卡拉塔格形成了一系列海相島弧火山巖,紅海VMS銅鋅礦床在第二巖性段巖漿噴發(fā)晚期形成于火山洼處,并隨著第三巖性段中酸性巖漿持續(xù)快速噴發(fā)使得紅海VMS銅鋅礦床得以迅速掩埋、保存。
[Abstract]:Karatagh is located in the southern margin of the Turpan-Hami basin in the East Tianshan Mountains and belongs to the Paleozoic accretionary island arc zone of Dananghu-Tousuquan. VMS porphyry skarn is mainly developed in the area. There are four types of ore-forming systems, such as subvolcanic hydrothermal type and copper-nickel sulfide, in which the VMS and subvolcanic hydrothermal deposits mainly occur in the Paleozoic strata. It can be divided into three lithologic sections from the bottom to the top. In this paper, the volcanic rock samples are collected systematically and the main trace amount of the rocks is carried out by using the measured geological profile. Sr-Nd isotopes and SIMS zircon U-Pb isotopic experiments. The ore-bearing strata in the late early Paleozoic in Karatagh nuclear area belong to the Daliugou formation. The first lithologic member of the volcanic rock of the Daliugou formation is marine meso-basic volcanic rock. The upper limit of its formation age is the late Ordovician calc-low calc-calc-alkaline, which is characterized by the enrichment of large ion lithophile elements, such as LREE and RbPU UK, as well as PBO Th. The second lithologic member of the volcanic rocks of the Daliugou formation is marine neutral volcanic rocks and pyroclastic rocks. The upper limit of its formation time is the early Silurian Silurian (440Ma), which is obviously affected by the hydrothermal action on the bottom of the sea, resulting in a strong yellowish sericite, green mud fossilization and silicification. It is rich in large ion lithophile elements, such as LREE and RbBX, but depleted in NB, Ta and P. Ti. the third lithologic member of the volcanic rocks of the Daliugou formation is shallow-marine intermediate-acid volcanic rocks and pyroclastic rocks, the upper limit of which is the late Silurian to the early Devonian Jiao 420 Mai, low potassium and sodium rich. From neutral volcanic rocks to acidic volcanic rocks, the total amount of rare earth elements increases gradually with the order of magmatic differentiation and evolution from no anomaly to obvious negative anomaly. K and other large ion lithophile elements, but depleted elements such as NbTa-Ta-Pu, Ti-Li and Sr. The Daliugou formation as a whole shows typical geochemical characteristics of island arc magma, the third lithologic member is obviously rich in sodium, and the first is the first. The alteration of volcanic rocks in the second lithologic member is very strong, and its Na2O content decreases. Sr-Nd isotope shows that the 87 Sr / 86 Sr ~ (-) I of volcanic rock is between 0.704701 ~ 0.707351 and 0.707351. 蔚 Ndndt) is between 2.12 and 7.44, and the intermediate acid magmatic rock intruding into this set of volcanic strata is between 0.70377070 and 0.705203, and the intermediate acid magmatic rock with 87s r-86SrtI is between 0.703770 and 0.705203. 蔚 Ndct) is between 5.66 and 6.84, indicating that it originated from the depleted mantle and was contaminated by weak crustal materials, but obviously influenced by sea water, and subducted southward with the Kalamaili Ocean. A series of marine island arc volcanic rocks were formed in Karatagh, and the VMS copper-zinc deposit in the Red Sea formed in the volcanic depression in the late stage of magmatic eruption in the second lithologic section. Along with the rapid eruption of intermediate acid magma in the third lithologic section, the VMS copper and zinc deposit in the Red Sea can be buried and preserved rapidly.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P59;P536

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