内蒙古东升庙矿区狼山群中变质“双峰式”火山岩夹层的确认及其意义  

THE CONFIRMATION OF THE METAMORPHIC DOUBLE PEAKING VOLCANIC ROCKS IN LANGSHAN GROUP OF THE DONGSHENGMIAO ORE DISTRICT, INNER MONGOLIA AND ITS SIGNIFICANCE

作　　者：彭润民[1] 翟裕生[1] 

机构地区：[1]地质矿产系

出　　处：《地球科学（中国地质大学学报）》1997年第6期587-594,共8页Earth Science-Journal of China University of Geosciences

基　　金：化学工业部地质研究课题;国家科委攀登计划

摘　　要：东升庙矿床狼山群二组含矿地层中石英钠长浅（变）粒岩类（Ⅰ类，ｗ（ＳｉＯ２）＝７０．４７％～７３．０２％）、黑云钠—更长片岩类（Ⅱ１类，ｗ（ＳｉＯ２）＝５２．００％～５４．４３％）和钠—更长绿泥（角闪）片岩类（Ⅱ２类，ｗ（ＳｉＯ２）＝４７．４４％～４８．８６％）具如下特征：（１）稳定呈层产出，并与上、下相邻地层一道褶皱、变形；（２）含有变余斑晶和晶屑；（３）轻稀土元素富集，重稀土元素亏损；（４）多种岩石化学图解一致表明它们是正变质岩；（５）Ⅰ类与Ⅱ１类呈上、下层关系连续产出等特征，确认它们都是变质火山岩夹层，并具有“双峰式”组合．研究表明本矿床形成于元古宙大陆边缘的裂谷盆地．The host succession, Langshan Group, of the Dongshengmiao deposit has been studied for many years. It is believed that the quartz-albite leucogranulites or granulites (type Ⅰ, w (SiO 2)=70.47%～73.02%), the biotite-albite-oligoclase schists (type Ⅱ 1, w (SiO 2)=52.00%～54.43%) and the albite-oligoclase-chlorite (hornblende) schists (type Ⅱ 2, w (SiO 2)=47.44%～48.86%) in the second formation of Langshan Group are metamorphic volcanic rocks, and the assemblage of them has the double-peaking characteristics based on the following facts and features: (1)they occur in beds, and are folded or deformed in concordance with the overlying and underlying strata; (2)they all have blastoporphyritic and blastocrystalloclastic crystals which consist of major albite and minor quartz for type Ⅰ, major albite or oligoclase and minor pyroxene for type Ⅱ 1, and major albite or oligoclase and minor hornblende for type Ⅱ 2; (3)the REE composition of them is enriched in light REEs and depleted in heavy REEs; (4)the results of the petrochemical diagrams show that they are orthometamorphites; (5)the type Ⅱ 1 is directly underlying the type Ⅰ. The existence of the metamorphic double-peaking volcanic rocks in the second ore-bearing formation of Langshan Group in the Dongshengmiao ore district suggests that the ore deposit was formed in the tensional rift basin along the north margin of the North China platform during Mesoproterozoic time and is conducive to synthetic and systematic analyses of the ore-forming process of the ore deposit, to the regional strata correlation and the following ore prospecting in the outskirts of the ore district.

关 键 词：火山岩 狼山群 东升庙矿床 内蒙古 岩石夹层 

分 类 号：P588.14[天文地球—岩石学]