大兴安岭北段霍洛台地区辉绿玢岩的锆石U-Pb年龄、岩石成因和构造背景

Zircon U-Pb age,petrogenesis,and tectonic setting of the diabase porphyrite in the Huoluotai area,northern segment of the Great Xing an Range

对于大兴安岭北段中生代火成岩的研究,在中酸性花岗岩和火山岩等方面已有诸多成果,相比之下,对于该区中生代基性岩浆岩具体的形成时代和岩石成因仍不明确。而且,大兴安岭北段晚侏罗世-早白垩世的构造背景也存在争议。为此,本文对大兴安岭北段霍洛台地区辉绿玢岩进行了锆石U-Pb年代学和岩石地球化学特征研究,以达到进一步明确大兴安岭北段晚中生代基性岩浆岩的形成时代、岩石成因及其构造背景的目的。结果表明:霍洛台地区辉绿玢岩锆石的加权平均年龄为(129.1±1.3) Ma,属于早白垩世;辉绿玢岩稀土元素配分曲线为平坦型,Eu异常不明显;富集大离子亲石元素(如Ba、Sr),亏损高场强元素(如Th、Ce、Ti)。霍洛台辉绿玢岩可能起源于俯冲流体交代的岩石圈地幔源区,其形成可能受到了古太平洋板块俯冲作用的影响。

The study of Mesozoic igneous rocks in the northern segment of the Great Xing an Range has yielded significant results,particularly in the areas of intermediate to acidic granites and volcanic rocks.However,research on the specific formation ages,petrogenesis,and tectonic settings of Mesozoic mafic igneous rocks in this region has been relatively scarce.Moreover,there is ongoing debate regarding the tectonic setting of the northern segment of the Great Xing an Range during the Late Jurassic-Early Cretaceous.Therefore,in order to further clarify the formation age,the petrogenesis and tectonic setting of the late Mesozoic basic magmatic rocks in the northern segment of the Great Xing an Range,the zircon U-Pb chronology and petrogeochemical characteristics of diabase porphyrite in the Huoluotai area were studied.The results show that the weighted mean zircon age of diabase porphyrite in the Huoluotai area is(129.1±1.3)Ma,which belongs to Early Cretaceous.The REE partition curve of diabase porphyrite is flat,and the Eu anomaly is not obvious.The samples are enriched in large-ion lithophile elements(e.g.,Ba and Sr),depleted in high-field-strength elements(e.g.,Th,Ce,and Ti).It is believed that the Huoluotai diabase porphyrite originated from the lithospheric mantle source that had previously been metasomatized by slab-derived fluids,and its formation may have been influenced by the subduction of the Paleo-Pacific Plate.