Petrology, Geochemistry Characteristics and Genesis of the Mid Jurassic Volcanic Rocks of the Lanqi Formation, Qinglong Orefield
Abstract: The Lanqi volcanic rocks at mid Jurassic are composed of a series of intermediate volcanic rocks and volcanic-clasitic rocks. They are the most important protecting thick cover on the orebody. This formation could be divided into three layers based on the volcanic petrography feature: the lower—andesitic agglomerate, breccia, porphyroclast and andesite; the middle—the purple Red tuffaceous sandstone and conglomerate; the upper—vesicular andesite with thin layer black mica crystal tuff. The Lanqi volcanic rocks are characterized by low MgO value, low TiO2 value, high Al2O3 value and high K2O value, belonging to quasi-aluminous, high-k calc-alkaline series. The REE, compatible elements and incompatible elements suggest that lower crust magma is mixed with some mantle magma and shows a trend of strong-weak-strong of contamination levels in different stages. The formation of magma is not due to the Large-scale crystallization differentiation, but probably mainly due to the partial melting. The tectonic setting is at intraplate orogeny, on the stage of transformation from the earthcrust shorting thickening to thining.
文章引用: 李国臣 , 孙 祥 , 罗 毅 , 谷 勇 (2015) 青龙矿田兰旗组火山岩岩石学、地球化学特征及成因探讨。 自然科学， 3， 40-48. doi: 10.12677/OJNS.2015.32006
 赵越, 徐刚, 张拴宏, 等 (2004) 燕山运动与东亚构造体制的转换. 地学前缘, 3, 319-328.
 李伍平, 路凤香, 李献华, 等 (2001) 北京西山髫髻山组火山岩的火山岩地球化学特征与岩浆起源. 岩石矿物学杂志, 2, 123-133.
 Gao, S., Rudnick, R.L., Yuan, H.L., et al. (2004) Recycling lower conditiontal crust in North China craton. Nature, 432, 892-897.
 Davis, G.A. (2003) The Yanshan belt of North China, Tectonics, adakitic, magmatism, and crustal evolution. Earth Science Frontiers, 10, 373-384.
 杨富全, 吴海, 刘晓文, 等 (2003) 冀北甲山正长岩——燕山陆内造山带岩石圈减薄的早期记录. 地质论评, 5, 474-485.
 李伍平, 李献华, 路凤香, 等 (2002) 辽西早白垩世义县组火山岩的地质特征及其构造背景. 岩石学报, 2, 193- 204.