CAJ | 학술논문

祁连山西段吊大坂新元古代花岗质片麻岩出露于北大河岩群二云母片麻岩中。地球化学特征显示，吊大坂新元古代花岗质片麻岩主要为碱性、弱过铝质花岗岩(A/CNK=1.04~1.12)。岩石主体Rb含量较低，Sr和Ba含量高，K/Rb值介于179~225之间，说明吊大坂新元古代花岗质片麻岩不是高分异花岗岩，但明显的负Eu异常（Eu/Eu?=0.25~0.35），说明该岩浆经历了弱的分离结晶作用。在(Al2O3+TFeO+MgO+TiO2)-Al2O3/(TFeO+MgO+TiO2)图解中，未经历强烈分异的花岗质岩石样品点落入地壳杂砂岩或中性岩浆岩源区。未经历强烈分异的样品富集强不相容元素，并且在Y-Nb和(Y+Nb)-Rb图解中，主体落入板内花岗岩区域。吊大坂花岗质片麻岩LA-ICP-MS锆石206Pb/238U年龄为736±5Ma，该年龄被解释为花岗质片麻岩的形成时代，说明祁连山存在750~730Ma的岩浆作用记录，可能为新元古代晚期伸展背景下的产物。祁连山新元古代岩浆活动记录了新元古代早期汇聚、新元古代晚期伸展到裂解的长期演化过程。
기련산서단조대판신원고대화강질편마암출로우북대하암군이운모편마암중。지구화학특정현시，조대판신원고대화강질편마암주요위감성、약과려질화강암(A/CNK=1.04~1.12)。암석주체Rb함량교저，Sr화Ba함량고，K/Rb치개우179~225지간，설명조대판신원고대화강질편마암불시고분이화강암，단명현적부Eu이상（Eu/Eu?=0.25~0.35），설명해암장경력료약적분리결정작용。재(Al2O3+TFeO+MgO+TiO2)-Al2O3/(TFeO+MgO+TiO2)도해중，미경력강렬분이적화강질암석양품점락입지각잡사암혹중성암장암원구。미경력강렬분이적양품부집강불상용원소，병차재Y-Nb화(Y+Nb)-Rb도해중，주체락입판내화강암구역。조대판화강질편마암LA-ICP-MS고석206Pb/238U년령위736±5Ma，해년령피해석위화강질편마암적형성시대，설명기련산존재750~730Ma적암장작용기록，가능위신원고대만기신전배경하적산물。기련산신원고대암장활동기록료신원고대조기회취、신원고대만기신전도렬해적장기연화과정。
Neoproterozoic granitic gneisses from the Diaodaban area of the western Qilian Mountain outcrop in two-mica gneiss of the Beidahei Group. The granitic gneisses are mainly alkaline and peraluminous, with A/CNK values of 1.04~1.12. Their low Rb values and high Sr and Ba values as well as K/Rb ratios of 179~225 show that the rocks are not highly fractionated granite;nev?ertheless, the rocks have obvious negative Eu anomaly (Eu/Eu?=0.25~0.35), indicating that the magma experienced weak fraction?ation crystallization. The diagram of (Al2O3+TFeO+MgO+TiO2)-Al2O3/(TFeO+MgO+TiO2) suggests that the protolith of the rocks was sourced from graywacke or mafic-intermediate igneous rocks. Samples are enriched in incompatible elements and have geochemical characteristics of the intraplate granite in Y-Nb and (Y+Nb)-Rb diagrams. LA-ICP-MS zircon U-Pb dating of the granitic rocks yielded a weighted mean age of 736 ± 5Ma, suggesting that there is a magmatic record of 750~730Ma in the Qilian Mountain, probably resulting from intraplate extension in the late Neoproterozoic. The Neoproterozoic magmatic activities in the Qilian Mountain recorded a long-term evolution history from early Neoproterozoic convergence through Late Neoproterozoic ex?tension to breakup.