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流水沟岩浆杂岩分布于西秦岭北缘天水关子镇地区,主要由变辉长岩、变辉长闪长岩和变闪长岩组成。为确定其构造属性,探讨西秦岭北缘构造演化过程,对其进行了LA-ICP-MS锆石U-Pb测年和主量、微量、稀土元素分析。结果表明,岩浆杂岩体的锆石为岩浆成因,其形成时代为548.7Ma±1.8Ma(MSWD=0.56)。流水沟岩浆杂岩具有SiO2变化范围大(52.47%～66.95%),低TiO2,低碱,Mg#值变化范围较大的特征,主量元素在SiO2-氧化物变异图解上具有较好的线性相关性。稀土元素配分曲线总体呈近平坦型,LREE/HREE比值多数在1.14～2.60之间,轻重稀土元素分馏较弱,δEu介于0.65～1.90之间,大多数具有弱的负Eu异常;在微量元素蛛网图上,大离子亲石元素Cs、Sr、Th、U富集,Rb、K和高场强元素Nb、P、Ti、Y亏损,Ti/Y=113～253,Th/Yb=0.23～2.85,Th/Nb=0.09～1.00,Hf/Th=0.41～2.97,显示了流水沟岩浆杂岩形成于岛弧环境。流水沟岩浆杂岩可能反映在中央造山系中存在一期与“泛非造山运动”有关的构造热事件,为中央造山系在新元古代晚期—早古生代的构造演化提供了证据。
Liugou magmatic complexes are distributed in the Guanzizhen area of Tianshui, the northern margin of the Western Qinling Ridge, and are mainly composed of gabbro, gabbro diorite and diorite. In order to confirm its tectonic property, the tectonic evolution of the northern margin of the West Qinling Mountains was discussed. LA-ICP-MS zircon U-Pb dating and major, trace and rare earth elements were analyzed. The results show that zircons of magmatic complexes are magmatic origin, forming 548.7Ma ± 1.8Ma (MSWD = 0.56). The MgO has the features of wide range of SiO2 (52.47% -66.95%), low TiO2, low alkali and large Mg # value. The main elements have good linearity in the graph of SiO2-oxide variation Correlation. The LREE / HREE ratio is mostly in the range of 1.14-2.60. The fractional fractionation of light and heavy rare earth elements is weak, δEu is between 0.65 and 1.90, and most of them have weak negative Eu anomalies. In the trace elements On the cobweb map, the enrichment of large ion lithophile elements Cs, Sr, Th, U, Rb, K and depletion of high field strength elements Nb, P, Ti and Y, Ti / Y = 113 ~ 253, Th / Yb = 0.23 ~ 2.85, Th / Nb = 0.09-1.00, Hf / Th = 0.41-2.97, indicating that the Shui Shuiou magmatic complex formed in the island arc environment. Lugou magmatic complexes may reflect the existence of a tectono-thermal event related to “Pan-African orogenic movement” in the central orogenic system and provide evidence for the tectonic evolution of the Central orogenic system in the Neoproterozoic-Early Paleozoic.