本文選題：鋯石U-Pb定年 + 混合作用�。� 參考：《巖石學(xué)報》2017年03期

【摘要】：古特提斯洋在三疊紀時期沿現(xiàn)今勉略縫合帶的閉合,標志著華北板塊(NCB)和揚子板塊(YZB)的最終拼貼完成。秦嶺造山帶西段發(fā)育印支期花崗巖漿活動,為該地區(qū)的成礦作用提供了有利的條件。對這些巖漿巖的形成時代、地化屬性、演化、來源等的研究將有助于了解該時期的構(gòu)造背景及動力學(xué)環(huán)境。本文以西秦嶺北亞帶的江里溝復(fù)式巖體作為研究對象,通過LA-ICP-MS鋯石U-Pb測年、鋯石Hf同位素測試和主微量元素分析,對該巖體進行了系統(tǒng)的研究。結(jié)果顯示:江里溝復(fù)式巖體的三種主要巖性為斑狀黑云母二長花崗巖、花崗斑巖和細�；◢弾r,加權(quán)平均年齡分別為:229.1±1.8Ma(MSWD=0.82)、222.5±1.4Ma(MSWD=0.41)和217.1±1.8Ma(MSWD=1.4),指示該巖體形成于晚三疊世。其地球化學(xué)性質(zhì)具有高硅(SiO_2=72.67%~77.84%),富堿(K_2O+Na_2O=7.67%~8.75%),弱過鋁質(zhì)(A/CNK=1.01~1.06),高度分異(巖體由早至晚DI及Rb/Sr均升高,DI=88.9~95.36,Rb/Sr=1.76~12.19),富集Rb、Th、U、Ta、Zr、Hf和HREE元素特點,虧損Ba、Sr、P、Ti等元素;三個侵入體均發(fā)育明顯負Eu異常(δEu=0.54~0.62、0.26~0.47、0.20~0.60);P_2O_5含量與SiO_2呈明顯的負相關(guān)關(guān)系,而Y的含量反之,綜合判定認為,巖體屬高分異I型花崗巖。巖石形成溫度從早至晚明顯降低(平均由786℃至755℃)。εHf(t)值少數(shù)0外,絕大多數(shù)介于0.1~4.8之間,相應(yīng)tDM2=0.95~1.25Ga。綜合推斷認為,江里溝巖體的原始巖漿是由部分熔融的巖石圈地幔與中新元古代的地殼混合,形成的混合巖漿,后經(jīng)強烈的結(jié)晶分異作用形成江里溝復(fù)式巖體。
[Abstract]:The closure of the PaleoTethys Ocean in the Triassic along the present Mian suture zone marks the completion of the final collage of the North China Plate (NCBB) and the Yangtze Plate (YZB). Indosinian granitic magma was developed in the western part of Qinling orogenic belt, which provides favorable conditions for mineralization in this area. The study of the age, geochemistry, evolution and source of these magmatic rocks will be helpful to understand the tectonic background and dynamic environment of the period. The Jiangligou complex rock mass in the northern subzone of the Qinling Mountains west of this paper was studied systematically by LA-ICP-MS zircon U-Pb dating zircon HF isotope test and principal trace element analysis. The results show that the three main lithologic types of the Jiangligou complex are porphyry biotite monzogranite, granitic porphyry and fine-grained granite, with weighted mean ages of 229.1 鹵1.8 Mai MSWD 0.42 鹵222.5 鹵1.4 Ma-MSWDU 0.41 and 217.1 鹵1.8 Ma-MSWD1.4T respectively, indicating that the rock was formed in the late Triassic. Its geochemical properties are high SiOS _ 2 / 72.67 / 77.84, alkali-rich K _ 2O Na _ 2O 7.67 and 8.75m, weak peraluminous / ACNK _ (1.01C) 1.01C ~ (1.06C), high differentiation (the rock mass increases from early to late, DI and Rb/Sr are higher than RbSrLi 1.7612.19), rich in elements such as RbThU, HREE, and so on. The negative EU anomaly (未 EU ~ (0.54) 0.62) 0.260.260.70 ~ (0.20) 0.20 ~ (0.60) P _ 2O _ 5 is negatively correlated with SiO_2 in all the three intrusions, whereas the Y content is the opposite. It is considered that the rock mass belongs to high-grade hetero-I-type granite. The formation temperature of the rocks decreased obviously from early to late (from 786 鈩，

本文編號：1901596