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内蒙古东北部阿龙山地区的早白垩世花岗岩岩体就位于火山喷发形成的塌陷破火山口中央或火山断裂中,岩石类型有石英二长(斑)岩、晶洞正长花岗岩、文象碱长石英正长岩等。岩石普遍具文象结构、晶洞构造,但未见碱性暗色矿物;岩石化学上具高硅、富碱和富铝、低钛镁等特征,且岩石中富集高场强元素(HFSE),在微量元素蛛网图中出现Sr、Ba相对亏损,稀土配分曲线呈轻稀土富集的不对称右倾“海鸥”型,δEu亏损中等,岩石具较低的εNd(t)值(-3.00)和低的86Sr/87Sr初始值(0.708734)。以上岩体的岩石学、主微量元素及同位素特征表明,岩体具有铝质A1型花岗岩的特征,其成因与陆内巨量火山喷发造成的伸展、崩塌机制有关,反映了非造山板内拉张的构造环境。
The Early Cretaceous granitic intrusions in the A Longshan area, northeastern Inner Mongolia, are located in central or volcanic faults in the collapsed caldera formed by volcanic eruptions. The types of rocks are quartz diorite (plagioclase), granodiorite granite, Quartz sandstone and so on. The rocks are generally characterized by textural structure and crystal cave structure, but no alkaline dark mineral is found. The rock chemistry is characterized by high silicon, alkali-rich and rich in aluminum, low titanium and magnesium. The rock is rich in high field strength elements (HFSE) , Sr and Ba were relatively depleted in the trace element cobweb, and the REE distribution curve showed an asymmetric right-leaning “Seagull” type with light rare earth enrichment with a moderate δEu loss. The rock had a relatively low εNd (t) value (-3.00 ) And a low 86Sr / 87Sr initial value (0.708734). The petrology, major trace elements and isotopic characteristics of the above rock mass indicate that the rock mass has the characteristics of aluminum A1 type granite. The genesis of the rock mass is related to the extension and collapse mechanism caused by volcanic eruptions in the interior of the block. Zhang’s construction environment.