【摘要】：內(nèi)蒙古中部紅格爾地區(qū)堿長(zhǎng)花崗巖是白音烏拉-東烏旗A型花崗巖帶的重要組成部分,其LA-ICP-MS鋯石U-Pb年齡為286~294 Ma,表明其形成時(shí)代為早二疊世。巖石富硅(SiO_2=75.13%~80.17%)、富堿(Na_2O+K_2O=7.33%~9.11%)、富鐵(TFe_2O_3=1.01%~2.31%)、貧鎂(MgO=0.09%~0.27%)和貧鈣(CaO=0.12%~0.52%)。微量元素中大離子親石元素(LILE)Rb、Th、K和Pb明顯富集,Sr、Ba強(qiáng)烈虧損;高場(chǎng)強(qiáng)元素(HFSE)Nb、Ti、La和Ce虧損明顯,Zr、Hf相對(duì)富集。巖體稀土總量較低且變化大(∑REE=33~165μg/g),輕重稀土分異程度低且輕稀土弱富集,具明顯的Eu負(fù)異常(δEu=0.06~0.13),稀土元素分布模式表現(xiàn)為較平緩、輕微右傾的海鷗型分布型式。εNd(t)為正值(+1.08~+3.18),tDM2變化于805~965 Ma之間;有較高的放射成因鉛,(~(206)Pb/~(204)Pb)i為18.710~19.280,(207Pb/204Pb)i為15.557~15.597,(~(208)Pb/~(204)Pb)i為37.887~38.330。巖石學(xué)、主元素和微量元素地球化學(xué)特征顯示紅格爾地區(qū)堿長(zhǎng)花崗巖屬于鋁質(zhì)A型花崗巖,其形成于碰撞后伸展構(gòu)造背景,是后碰撞俯沖板片斷離誘發(fā)中下地殼鎂鐵質(zhì)巖石部分熔融的產(chǎn)物。紅格爾地區(qū)A型花崗巖的發(fā)育可能反映了內(nèi)蒙古中部古亞洲洋在二疊紀(jì)前已經(jīng)閉合。
[Abstract]:Alkali-feldspar granites are an important part of the Baiyinwula-Donwuqi A-type granite belt in central Inner Mongolia. Its LA-ICP-MS zircon U-Pb age of 2860.294 Ma, indicates that it was formed at an early Permian age. The rocks are rich in silicon (SiO_2=75.13%~80.17%), alkali-rich (Na_2O K _ 2O-7.33%), and rich in iron (TFe_2O_3=1.01%~2.31%), Poor magnesium (MgO=0.09%~0.27%) and poor calcium (CaO=0.12%~0.52%). The large ion lithophile elements (LILE) Rb,Th,K and Pb) and the high field strength elements (HFSE) Nb,Ti,La and Ce) were obviously enriched in microelements, and the Sr,Ba was strongly depleted, while the Zr,Hf was relatively enriched in high field strength elements (HFSE) Nb,Ti,La and Ce). The total amount of rare earth in rock mass is low and large (鈭，

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