Geochemical Characteristics of the Calc-Silicate Rocks in Khondalite Series in Daqingshan Area,Inner Mongolia
Geochemical Characteristics of the Calc-Silicate Rocks in Khondalite Series in Daqingshan Area,Inner Mongolia
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发表时间：
2005
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通讯作者：
Xu Zhongyuan;Liu Zheng-hong;Huang Feng-xiang;Yang Zhensheng
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作者：
Xu Zhongyuan;Liu Zheng-hong;Huang Feng-xiang;Yang Zhensheng
在内蒙古大青山地区孔兹岩系中，迪片麻岩组合是一个独立的岩石地层单元，其特点是钙硅酸盐岩覆盖于嘎比片麻岩组合之上，上覆有大理岩组合。其特点是一般含有透辉石、榍石、方沸石和磷灰石，由透辉石片麻岩（DG）和透辉长石组成。麻粒岩(DFG)、长石透辉石麻粒岩(FDG)、透辉石(DD)和透辉石大理岩(DM)。该组合物富含Ca、Sr、Na,贫Cr、Ni、Co、Sc,表明该单元内存在化学沉积物。此外,CaO和Al_2O_3与SiO_2的正相关性反映了碎屑岩丰度增加和化学沉积物减少的趋势。沉积物从DM经DD、FDG到DFG和DG。主量、微量和稀土元素特征表明原岩组合为(富铁)白云质泥岩、钙质泥岩和杂砂岩夹泥质灰岩和泥灰岩、含钙长石砂，沉积于干燥、潮间带或泻湖等陆源碎屑物质供给不足的环境中。地球化学中的GaBi片麻岩，特别是稀土元素，当单独考虑化学沉积物时，反映出它们可能与GaBi片麻岩具有共同物源。迪片麻岩组合、GaBi片麻岩组合和大理岩组合构成了从碎屑到化学混合碎屑到化学沉积的沉积旋回，是中元古代长城群的沉积特征，从而支持了孔达岩系沉积于克拉通内的观点。盆地。
In the khondalite series in Daqingshan area,Inner Mongolia,Di gneiss association is a independent litho-stratigraphic unit characteristic of calc-silicate rocks overlying a GaBi gneiss association and being overlain by a marble association.Characterized by generally containing diopside,sphene,scapolite and apatite,the unit is composed of diopside gneisses(DG) and diopside-feldspar granulitite(DFG),feldspar-diopside granulitite(FDG),diopsidite(DD) and diopside marble(DM).The association is rich in Ca,Sr,Na and depleted in Cr,Ni,Co,Sc,suggesting the presence of chemical sediments in the unit.Moreover,the negative correlation of CaO and positive of Al_2O_3 with SiO_2 reflect an increasing abundance of clastic rocks and a decreasing trend in chemical sediments from DM via DD,FDG to DFG and DG.The characteristics of major,trace and rare earth elements suggest a protolith association of(iron-rich) dolomitic pelite,calcareous mudstone and greywacke intercalated by pelitic limestone and marlite,calcareous-bearing arkose,which was deposited in the setting of dry,intertidal or laguna with insufficient supply of the terrigenous detrital material.Their similarity to GaBi gneiss in geochemistry,especially in REE,when chemical sediments are considered separately,reflects that they probably shared a mutual provenance to GaBi gneiss.The Di gneiss association,GaBi gneiss association and marble association make up a sedimentary cycle from clastic via clastic mixed by chemical to chemical sediment,a sedimentary feature characteristic of Mid-Proteroroic Changcheng Group,hence supporting the view that the khondalte series was deposited within an intracratonic basin.