本文選題：TTG + 巖石成因��； 參考：《巖石學(xué)報(bào)》2017年09期

【摘要】：通過詳細(xì)的野外地質(zhì)工作,本文在山西云中山地區(qū)識(shí)別出一套巖石組合完整的TTG片麻巖巖系,與TTG片麻巖共生的還有后期發(fā)育的二長花崗片麻巖。LA-ICP-MS鋯石U-Pb定年結(jié)果表明,花崗閃長質(zhì)片麻巖的形成時(shí)間為2486±9Ma,二長花崗片麻巖的形成時(shí)間為2448±11Ma。地球化學(xué)特征顯示研究區(qū)TTG片麻巖為高鋁TTG。奧長花崗質(zhì)片麻巖總體表現(xiàn)為高SiO_2(69.82%~73.54%)、富Na_2O(4.19%~5.16%)、高CaO(1.45%~3.03%)的特征,Al_2O_3含量為14.31%~15.74%,鋁飽和指數(shù)(A/CNK)為1.00~1.03,屬富鈉過鋁質(zhì)系列巖石;英云閃長質(zhì)片麻巖的特征與奧長花崗片麻巖基本相似,但K_2O含量更低,CaO含量更高;花崗閃長質(zhì)片麻巖SiO_2(61.23%~61.97%)含量相對偏低,Na_2O/K_2O為1.00~1.32,Al2O3含量為15.03%~15.73%,鋁飽和指數(shù)(A/CNK)為0.96~1.05,為準(zhǔn)鋁質(zhì)或過鋁質(zhì)系列巖石。與上述TTG片麻巖不同的是,本區(qū)出露的二長花崗片麻巖表現(xiàn)為富鉀(K_2O/Na_2O=1.22~1.44)、貧Al_2O_3(12.81%~14.27%)的特征。巖石稀土總量較低(∑REE=52.71×10~(-6)~262.0×10~(-6)),輕稀土富集,重稀土虧損,輕、重稀土強(qiáng)烈分餾。微量元素具有富集K、Rb、Th等大離子親石元素,虧損Nb、Ta、Sr、P、Ti等元素的特點(diǎn),Cr、Ni等相容元素含量也較低,表現(xiàn)出島弧巖漿的特征�；◢忛W長片麻巖和二長花崗片麻巖εHf(t)值均為正值,前者成巖年齡與二階段模式年齡較為接近,暗示其來源為2.5~2.6Ga的新生地殼,而后者成巖年齡與二階段模式年齡則相差較多,其測點(diǎn)大都落在2.7~2.8Ga地殼演化線的區(qū)域內(nèi),表明二長花崗片麻巖來自于2.7~2.8Ga的古老地殼。根據(jù)上述地球化學(xué)特征,并結(jié)合區(qū)域地質(zhì)特征,推測研究區(qū)高Al的TTG片麻巖是"平俯沖"狀態(tài)下洋殼部分熔融的產(chǎn)物,而二長花崗片麻巖為底侵古老地殼部分熔融的產(chǎn)物,形成于大陸邊緣弧的構(gòu)造環(huán)境,代表云中山地區(qū)一次重要的以水平增生為主的地殼生長事件,同時(shí)也表明在新太古代末期,云中山地區(qū)已完成克拉通化,進(jìn)入陸內(nèi)演化階段。
[Abstract]:Through detailed field geological work, a set of integrated TTG gneiss series has been identified in Yunshan area, Shanxi Province. The zircon U-Pb dating results show that TTG gneiss is associated with TTG gneiss, and later developed Erchang granitic gneiss. LA-ICP-MS zircon U-Pb dating results show that TTG gneiss is associated with TTG gneiss. The formation time of granodiorite gneiss is 2486 鹵9 Ma, and that of Erchang granitic gneiss is 2448 鹵11 Ma. The geochemical characteristics indicate that the TTG gneiss in the study area is high alumina TTG. The Al2O3 content is 14.31% and 1.001.03%, respectively. The Al2O3 content is 14.31% and 1.001.03%, respectively. The Al2O3 content is 1.001.03% and 1.001.03%, respectively, and the characteristics of the amphiolite gneiss are basically similar to those of the amphiolite gneiss, which is characterized by high SiO2 (69.822%), Na2O rich (4.1920%), high Cao (1.45% 3.03%), and aluminum saturation index (Ar / CNK) 1.001.03%, respectively, and is similar to that of the amphiolite gneiss. The content of SiO2 (61.23%) of granodiorogenic gneiss is relatively low. The content of K _ 2O / K _ 2O is 1.001.32%. The content of Al _ 2O _ 3 is 15.03 ~ 15.73, and the saturation index of aluminum is 0.96 ~ 1.05, quasi-aluminous or peraluminous series rocks. Different from the TTG gneiss mentioned above, the gneiss of Erchang granitic in this area is characterized by K _ 2O / Na _ 2O _ (1.221.44) and Al2O3 (12.81 ~ 14.27%). The total amount of REE in rock is low (鈭，

本文編號：2058851