本文選題：花崗巖　切入點(diǎn)：巖相學(xué)　出處：《東華理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：甘肅龍首山芨嶺地區(qū)為祁連-秦嶺鈾成礦省之龍首山-祁連山鈾成礦帶的重要組成部分,也是我國堿交代熱液型鈾礦最為典型的地區(qū)�；◢弾r是該區(qū)堿交代型鈾礦化主要圍巖。受當(dāng)時(shí)研究手段、測試方法等局限,前人對(duì)該區(qū)花崗巖形成時(shí)代的精確厘定相對(duì)滯后。本次論文對(duì)龍首山芨嶺地區(qū)花崗巖開展巖相學(xué)、地球化學(xué)及鋯石LA-ICP-MS U-Pb定年等研究,探討花崗巖成巖時(shí)代、巖石成因、巖漿來源、巖漿演化及花崗巖與構(gòu)造演化之間的成因聯(lián)系。取得以下主要認(rèn)識(shí):(1)通過野外觀察及巖相學(xué)的研究,確定芨嶺地區(qū)花崗巖的巖性主要為黑云母二長花崗巖、二長花崗斑巖、花崗質(zhì)細(xì)晶巖及斑狀黑云母二長花崗巖。(2)芨嶺地區(qū)花崗巖的主量元素具富堿、低鎂特征,屬于準(zhǔn)鋁質(zhì)高鉀鈣堿性系列巖石。Harker圖解中Si O2與K2O呈正相關(guān)關(guān)系,與Na2O、Al2O3、Mg O、Ca O、Mn O、Ti O2、P2O5呈負(fù)相關(guān)關(guān)系,反映鉀鈉長石及鎂鐵礦物的結(jié)晶分異過程。(3)芨嶺地區(qū)花崗巖的稀土元素具LREE富集,HREE分餾相對(duì)不明顯特征,稀土元素總量較大,除LSS12-05 Eu具有強(qiáng)烈負(fù)異常外,其他樣品均表現(xiàn)出Eu弱負(fù)異常,弱虧損特征,可能與斜長石在巖漿源區(qū)部分熔融過程中的殘余有關(guān)。(4)芨嶺地區(qū)花崗巖的微量元素具相對(duì)富集Ba、Rb、Th、U等大離子親石元素(LILE)且相對(duì)貧Ta、Nb、Zr、Hf、Ti、P等高場強(qiáng)元素(HFSE)特征。不同類型花崗巖中,除花崗質(zhì)細(xì)晶巖在微量元素含量上與其他巖性差別較大外,其他類型花崗巖組成及特征均較相似。(5)芨嶺地區(qū)花崗巖的鋯石LA-ICP-MS U-Pb定年結(jié)果顯示,花崗巖的形成時(shí)代從早到晚可劃分為兩個(gè)年齡段:428.6±8.1Ma~412.8±9.0Ma及401.3±5.0Ma,屬于志留紀(jì)-泥盆紀(jì)巖漿作用的產(chǎn)物,記錄了芨嶺地區(qū)在加里東晚期到海西早期至少經(jīng)歷了兩期的巖漿作用。(6)芨嶺地區(qū)花崗巖屬于I型花崗巖,其巖漿物質(zhì)主要來源于地殼,可能也有部分幔源物質(zhì)混入,形成于后碰撞構(gòu)造環(huán)境。(7)從早期到晚期,芨嶺地區(qū)花崗巖演化的巖性由黑云母二長花崗巖→二長花崗斑巖→斑狀黑云母二長花崗巖→花崗質(zhì)細(xì)晶巖轉(zhuǎn)變,顏色由灰白色變成肉紅色。分異程度及交代結(jié)構(gòu)種類逐漸增加。造巖礦物堿性長石、石英增多,副礦物種類增多。主量元素Fe、Mg、Ti減少,Na增加,稀土總量及輕稀土含量先增后降。
[Abstract]:The Jiling area of Longshoushan in Gansu Province is an important part of the uranium metallogenic belt of the Longshou-Qilian Mountains in Qilian Qinling uranium metallogenic province. Granite is the main surrounding rock of alkali metasomatism uranium mineralization in this area. In this paper, the lithofacies, geochemistry and zircon LA-ICP-MS U-Pb dating of granites in the Jiling area of Longshoushan are studied, and the diagenetic age and petrogenesis of the granites are discussed. The source of magma, the genetic relationship between magma evolution and granite and tectonic evolution. (1) through field observation and petrographic study, it is determined that the lithology of granites in Jiling area is mainly biotite monzogranite. The main elements of granites in Erchang granitic porphyry, granitic granites and porphyry biotite binomorphic granites are alkali-rich and low-magnesium. They belong to the quasi-aluminous high-potassium calc-alkaline series rocks. Harker diagrams show a positive correlation between Sio _ 2 and K _ 2O. There is a negative correlation between Na _ 2O _ 3 Al _ 2O _ 3, mg _ 2O _ 3, mg _ 2O _ 3, mn, mn, O _ 2O _ 2 and P _ 2O _ 5, which reflects the crystallization differentiation process of potassium albite and magnetite. The rare earth elements of granites in Jiling area are characterized by LREE enrichment and hree fractionation, and the total amount of rare earth elements is relatively large. Except for the strong negative anomaly of LSS12-05 EU, the other samples showed weak negative anomaly and weak depletion of EU. It may be related to the residual of plagioclase in the partial melting process of magma source region.) the trace elements of granites in the Jiling area are relatively enriched in large ion lithophile elements such as Bahl RbTU) and are relatively poor in high field strength elements such as Ta-NbSe, ZrHfTI-P, etc., and the characteristics of HFSEs are found in different types of granites. The zircon LA-ICP-MS U-Pb dating results of granites in the Jieling area show that the composition and characteristics of other types of granites are similar to those of other types of granites, except that the contents of trace elements in granitic fine-grained rocks are quite different from those of other types of rocks. The granites can be divided into two age groups: 428.6 鹵8.1Ma~412.8 鹵9.0Ma and 401.3 鹵5.0 Ma, which belong to Silurian Devonian magmatism. It is recorded that the granites in the Jiling area experienced at least two periods of magmatism from the late Caledonian to the early Hercynian.) the granites in the Jiling area belong to I-type granites, whose magmatic material is mainly derived from the crust, and some mantle materials may also be mixed in. From the early to the late period, the lithology of granite evolution in Jiling area was changed from biotite monzogranite to biotite monzogranite. 鈫扙rchang granitic porphyry. 鈫扨orphyry biotite monzomorphic granite. 鈫扵he granitic fine-grained rocks change from grayish white to fleshy red. The degree of differentiation and metasomatism structure gradually increase. The alkaline feldspar, quartz and accessory minerals are increased. The total amount of rare earth and the content of light rare earth first increased and then decreased.
【學(xué)位授予單位】：東華理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.121;P597.3

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相關(guān)期刊論文 前1條

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本文編號(hào)：1645599