黑尖山花岗闪长岩位于东天山造山带晚古生代弧盆系之小热泉子—大南湖古生代残留弧内,通过分析其野外地质特征、岩相学、岩石地球化学以及锆石U-Pb年代学特征,探讨了其岩石成因、构造背景,为东天山地区古洋盆闭合、碰撞造山时限等洋-陆构造格局及其演化研究提供新的基础信息.电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,LA-ICP-MS)锆石U-Pb同位素定年结果显示黑尖山花岗闪长岩形成年龄为(373.0±3.0)Ma.岩石地球化学研究表明,花岗闪长岩具有高硅、准铝质、中-高钾钙碱性系列的Ⅰ型花岗岩特征;稀土元素总量变化范围为112.82 × 10-6～129.91 × 10-6,且轻/重稀土的比值变化范围为8.73～11.26(平均值为9.64),指示轻稀土相对重稀土富集,弱Eu负异常(δEu=0.77～0.85);样品富集大离子亲石元素(LILE,如Rb、Ba、K、U),亏损高场强元素(HFSE,如Ta、Nb和Ti)及P、Ta、Nb负异常明显;显示岛弧岩浆岩的特征,形成于板块俯冲的构造环境.综合区域地质特征、岩石地球化学和岩浆源区特征,黑尖山花岗闪长岩是东天山小热泉子—大南湖岛弧内晚古生代大规模中酸性岩浆侵入作用的同期产物,表明东天山黑尖山地区晚泥盆世花岗闪长岩是古大洋(古北天山洋)板片向北俯冲的岛弧背景产物;进一步说明东天山黑尖山地区泥盆纪晚期古大洋仍未闭合.
Petrogenesis and Tectonic Significance of Late Devonian Granodiorite in Heijinshan Area,Eastern Tianshan Orogenic Belt:Evidences from Petrology,Zircon U-Pb Geochronology,and Geochemistry
The Heijianshan granodiorite is located in the Xiao Requanzi-Dananhu Paleozoic residual arc of the Late Paleozoic arc-basin system in the eastern Tianshan orogenic belt.Clues from fieldwork,petrography,geochemistry and Zircon U-Pb geochronology were integrated to provide constraints on the tectonic setting in the Late Devonian.Geochemistry data shows that the granitic amphibo-lite is a set of type Ⅰ granite with the characteristics of high silica,quasi-aluminous,and medium-high potassium-calcium alkalinity.The total amount of rare earth elements varies from 112.82 x 10-6 to 129.91 x 10-6,and the light/heavy rare earth ratio varies from 8.73 to 11.26(mean value 9.64).Eu elements show weakly negative anomalies(δEu=0.77～0.85).The sample is enriched in large ion lithophile element(LILE,e.g.,Rb,Ba,K,U),lacking high-field strength elements(HFSE,e.g.,Ta,Nb,and Ti)and P,with significant negative anomalies in Nb and Ta.It shows the characteristics of island arc magmatic rocks.The inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb isotope dating results show that the weighted average ages of granitic amphibolites in the area are(373.0±3.0)Ma,indicating that the granodiorites were formed during the Late Devonian,and are contemporaneous products of large-scale Late Paleozoic medium-acidic magmatic intrusion in the Xiao Requanzi-Da Nanhu island arc of the east Tianshan Block.The combination of regional geological features,petrography and magma source area characteristics suggests that the Late Devo-nian granodiorite in the Heijinshan area of the east Tianshan block is a product of the island-arc of the northward subduction of the ancient oceanic plate.
万方数据
维普
