CAJ | 학술논문

南天山北缘乌什塔拉地区东泉戈壁岩体岩石类型为似斑状二长花岗岩及少量的镁铁质包体，锆石SHRIMP U-Pb定年结果显示，其形成时代为305±1 Ma。岩石富碱（K2O＋Na2O=7.58%~8.44%），富钾（K2O/Na2O=1.09~1.33），高Mg#（51.6~58.5）, A/CNK为0.92~1.00之间，属于准铝质高Mg#高钾钙碱性系列；富集轻稀土（LREE）、大离子亲石元素（Rb，K，Th，U），亏损重稀土（HREE）、高场强元素（Nb，P，Ti），强烈亏损Y（10.17×10-6~14.84×10-6）及Yb（1.054×10-6~1.374×10-6），弱-无的负Eu异常（0.60~0.99），总体表明东泉戈壁岩体为壳-幔岩浆混合成因，具有碰撞晚期花岗岩类的地球化学特点。结合区域地质资料，东泉戈壁岩体的侵位表明在塔里木板块与伊犁-中天山板块碰撞造山作用晚期的挤压环境中，由于幔源岩浆的底侵作用，使得下地壳底部物质发生部分熔融，并与幔源岩浆发生混合作用，指示南天山晚古生代残余海盆的闭合。东泉戈壁壳-幔岩浆混合型花岗岩的确立表明晚石炭世南天山地区一次重要的地壳垂向生长事件。
남천산북연오십탑랍지구동천과벽암체암석류형위사반상이장화강암급소량적미철질포체，고석SHRIMP U-Pb정년결과현시，기형성시대위305±1 Ma。암석부감（K2O＋Na2O=7.58%~8.44%），부갑（K2O/Na2O=1.09~1.33），고Mg#（51.6~58.5）, A/CNK위0.92~1.00지간，속우준려질고Mg#고갑개감성계렬；부집경희토（LREE）、대리자친석원소（Rb，K，Th，U），우손중희토（HREE）、고장강원소（Nb，P，Ti），강렬우손Y（10.17×10-6~14.84×10-6）급Yb（1.054×10-6~1.374×10-6），약-무적부Eu이상（0.60~0.99），총체표명동천과벽암체위각-만암장혼합성인，구유팽당만기화강암류적지구화학특점。결합구역지질자료，동천과벽암체적침위표명재탑리목판괴여이리-중천산판괴팽당조산작용만기적제압배경중，유우만원암장적저침작용，사득하지각저부물질발생부분용융，병여만원암장발생혼합작용，지시남천산만고생대잔여해분적폐합。동천과벽각-만암장혼합형화강암적학립표명만석탄세남천산지구일차중요적지각수향생장사건。
The Dongquangebi pluton is located in the Wushitala area of the northern margin of the South Tianshan, and is comprised mainly of porphyraceous monzonitic granite and a small amount of mafic microgranular enclaves. SHRIMP zircon U-Pb dating of porphyraceous monzonitic granite indicates that the weighted mean 206Pb/238U age is 305±1 Ma. These rocks are characterized by high-alkali (K2O+Na2O=7.58%~8.44%) and high-K (K2O/Na2O=1.09~1.33) and high Mg number (Mg#=51.6~58.5), with the A/CNK values between 0.92 and 1.00, which fall into the metaluminous high-Mg# and high-K calc-alkaline series. These rocks are also characterized by enrichment of LREE and LILE (Rb, K, Th and U) and depletion of HREE and HFSE (Nb, P and Ti), with slightly negative Eu anomaly (0.60~0.99) and strong depletion of Y (10.17×10-6~14.84×10-6) and Yb (1.054×10-6~1.374×10-6). These features suggest that the petrogenesis of the Dongquangebi pluton is magma mixing and the geochemical features of the Dongquangebi pluton belong to granitic rocks formed in the late-stage of a collisional orogeny. Combined with regional geological data, it is concluded that the Dongquangebi granitic pluton was derived from partial melting of the lower crust,with minor mixing with mantle-derived magma,due to the underplating of mantle-derived magma during the late-stage collision between the Tarim plate and Yili-Central Tianshan plate. The collisional magmatism in the South Tianshan indicates that the South Tianshan Late Paleozoic residual basin was closed in the Late Carboniferous, and the establishment of magma mixing of the Dongquangebi pluton indicates an important event of vertical growth of the continental crust in the South Tianshan.