江西德兴银山火山岩-次火山岩岩石学研究

银山火山岩次火山岩属于高钾钙碱性系列。化学成分以低Ｔｉ、Ｎａ，高Ｋ和相对富Ａｌ为特征。微量元素∑ＲＥＥ较低，Ｋ、Ｒｂ、Ｔｈ、Ｕ、Ｌａ、Ｃｅ富集和Ｔｉ、Ｔａ、Ｓｒ、Ｐ、Ｙｂ相对贫化。从第一旋回到第三旋回，随着ＳｉＯ２含量降低，Ａｌ２Ｏ３、ＦｅＯ、ＭｇＯ、ＣａＯ、Ｎａ２Ｏ含量以及∑ＲＥＥ、∑Ｃｅ／∑Ｙ、（Ｌａ／Ｙｂ）Ｎ逐渐升高，岩性由流纹岩流纹英安斑岩英安质熔岩和英安斑岩粗面安山斑岩，表现连续的反序演化。起源于下部地壳的英安质母岩浆同化混染了部分上地壳的硅铝层物质并演化形成以英安质岩浆为主、顶部有一层富ＳｉＯ２、Ｋ的流纹质岩浆、底部有少量粗面安山质岩浆的带状岩浆房。断裂构造诱发岩浆房自上而下逐层抽取喷发—侵位形成反序的火山岩次火山岩。

PETROLOGY OF THE VOLCANIC SUBVOLCANIC ROCKS FROM YINSHAN IN DEXING COUNTY,JIANGXI PROVINCE

Yinshan volcanic subvolcanic rocks belong to the high potassium calc alkali series.Lower contents of Ti,Na,REE,Ta,Sr,P and Yb and richer in K,Al,La,Ce,Rb,Th and U are its character.From first cycle to third cycle,the rock types change from rhyolite,then rhyodacite porphyry,and then dacitic lava and dacite porphyry to latite porphyry.With content decrease of SiO 2, the contents of Al 2O 3,FeO *,MgO,CaO,Na 2O,REE,∑Ce/∑Y and (La/Yb) N increase gradually,this shows the continuous reversed order.Dacitic parent magma deriving from lower crust assimilates and contaminates some materials rich in Si and Al in upper crust,and evolves into the zonal magma chamber which is dominated by dacitic magma and there is a layer of rhyolitic magma rich in SiO 2 and K on the top and a little latitic magma in the bottom.Fault resulted in the eruption and emplacement of the magma extracted from the top to the bottom of chamber and the formation of the volcanic subvolcanic rocks of reversed order.