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通过岩石学、地球化学和同位素年代学研究,从原划“布伦阔勒岩群”中识别出一套“双峰式”火山岩,英安岩锆石LAICP-MS U-Pb年龄结果显示该套岩石形成年龄为521.3±3.3Ma,为早寒武世产物.在岩石类型上,玄武岩和英安岩属于低钾岩石系列,玄武岩相对富集Rb、Ba、K、LREE,而亏损Nb-Ta、Th,源于受早期俯冲洋/陆壳流体交代的亏损地幔熔融源区.英安岩表现出富集LILE、Th,亏损Nb-Ta、Sr和Ti.两类岩石表现出不同的稀土元素配分模式和微量元素特征,并缺乏分异演化的趋势,反映二者的成因存在差别.结合其地球化学特征和实验岩石学资料,认为英安岩为玄武岩底侵提供热,基性下地壳在相对低压条件下部分熔融形成的.这套“双峰式”火山岩组合证实区域上早古生代存在一次大陆拉张环境下的构造-岩浆事件.结合区域上研究资料,古元古代布伦阔勒岩群至少包含以下3个组成部分:(1)古元古代布伦阔勒岩群;(2)印支期高压变质岩体;(3)早古生代火山-沉积岩组合.
Through the study of petrology, geochemistry and isotopic chronology, a set of “bimodal” volcanic rocks, dacite zircon LAICP-MS U-Pb The age results show that the formation age of this set of rocks is 521.3 ± 3.3Ma, which is a product of the Early Cambrian. On the rock types, basalts and dacite belong to the series of low-k rocks, and basalts are relatively enriched in Rb, Ba, K and LREE with a loss Nb-Ta, Th, originates from a depleted mantle melting source area that was replaced by earlier subducted ocean / continental crust fluids. The diagenesis shows enriched LILE, Th, depleted Nb-Ta, Sr, and Ti. REE patterns and trace element characteristics, and lack of differentiation and evolution trend, reflecting the differences between the two.The combination of its geochemical characteristics and experimental petrology data, that the amphibole basaltic basalts provide heat, basic The lower crust was partially melted at relatively low pressure, and this “bimodal” volcanic assemblage confirmed the existence of a tectono-magmatic event over the continental extension in the area during the Early Paleozoic. Combined with regional studies, The Bulunchuole Formation consists of at least the following three components: (1) (2) Indosinian metamorphic rocks, and (3) Early Paleozoic volcanic-sedimentary assemblages.