本文選題：革吉地區(qū)　切入點(diǎn)：邦巴巖體　出處：《地質(zhì)通報(bào)》2016年01期

【摘要】：邦巴巖體位于拉薩地塊西部革吉地區(qū),由主體花崗巖、花崗閃長(zhǎng)巖、閃長(zhǎng)質(zhì)包體及一系列近平行、南北向展布的花崗斑巖脈體組成。野外地質(zhì)調(diào)查和LA-MC-ICP-MS鋯石U-Pb定年表明,革吉地區(qū)白堊紀(jì)的兩期巖漿活動(dòng)分別發(fā)生在131~132Ma和127Ma。早期巖漿作用形成主體花崗巖、花崗閃長(zhǎng)巖及閃長(zhǎng)質(zhì)包體,具有以下特征:(1)明顯富集K、Cs等大離子親石元素,虧損Nb、Ti、Zr等高場(chǎng)強(qiáng)元素;(2)具有明顯的負(fù)Eu異常(Eu/Eu*=0.49~0.61)及負(fù)Ce異常;(3)具負(fù)εHf(t)值(-3.2~-0.3)及古老的地殼模式年齡(1.210~1.399Ga);(4)初始Sr同位素比值為0.70424~0.71472,εHf(t)值為-5.70~-5.54。晚期巖漿作用形成花崗斑巖脈體,具有以下特征:(1)富集K、Cs等大離子親石元素,強(qiáng)烈虧損Nb、Ta、Ti等高場(chǎng)強(qiáng)元素;(2)基本不具有負(fù)Eu異�；蚓哂休p微的負(fù)Eu異常(Eu/Eu*=0.74~0.87);(3)具有更老的Hf同位素地殼模式年齡(1.226~1.576Ga)及更負(fù)的大范圍變化的εHf(t)值(-6.1~-0.7)。晚期巖漿作用鋯飽和溫度(777~796℃)及輕稀土元素不飽和溫度(794~812℃)均高于早期巖漿的鋯飽和溫度(661~762℃)及輕稀土元素不飽和溫度(750~769℃)。上述特征表明,兩期巖漿作用均為中拉薩地塊古老基底部分與地幔物質(zhì)混染部分熔融的產(chǎn)物,隨著巖漿作用的持續(xù)進(jìn)行,巖漿中的古老地殼組分增加,熔體溫度也增加,可能與南向俯沖的班公-怒江洋殼回轉(zhuǎn)驅(qū)動(dòng)的地幔巖漿活動(dòng)向北遷移有關(guān)。
[Abstract]:The Bangba rock body is located in the Guerji area of the western Lhasa block and consists of the main granite granodiorite diorite and a series of near parallel and north-south spreading granitic porphyry veins.Field geological survey and LA-MC-ICP-MS zircon U-Pb dating indicate that the Cretaceous magmatic activities occurred in 131~132Ma and 127 Ma. respectively.The early magmatism formed the main granite, granodiorite and diorite inclusions, with the following characteristics: 1) enrichment of large ion lithophile elements such as KnCs, etc.浜忔崯Nb,Ti,Zr絳夐珮鍦哄己鍏冪礌;(2)鍏鋒湁鏄庢樉鐨勮礋Eu寮傚父(Eu/Eu*=0.49~0.61)鍙?qiáng)璐烠e寮傚父;(3)鍏瘋礋蔚Hf(t)鍊，

本文編號(hào)：1705569