米仓山区中～深变质岩系—“后河群”原岩类型研究

The Study on Primary Rock Type of Medium high Gfdde Metamorphic Houhe Group in M eichangshan Area

米仓山区中～深变质岩系一“后河群”属晋宁前期火山喷发经区域变质及后期叠加变质作用形成的——套片岩～片麻岩～混合岩系，原岩包括钙碱性～碱钙性～偏碱性、碱性的基性～中性～酸性火山熔岩系列。根据岩层组合、岩石组构、岩性变化趋势及其层间关系分为上、下两部，各部自下而上的原岩类型均包括玄武岩～安山岩～流纹岩的完整系列，且上部更富于ＳｉＯ＿２和碱（Ｋ＿２Ｏ＋Ｎａ＿２Ｏ），其火山岩的自然组合类型上部与黄石公园型相近，下部与埃特纳型相同。

AbstractThe medium──high grade metemorphic rocksries,localled houhe group ,belong to pro一JinlingPeriod Voicanic erup一tionsundergone areal metamorphism and later adding metamorphism,forming shists , gneisses一migmatites. The Primary rocks of the formation include Cal一aikalito alk一Cal and Subalkaline,and alkalibasaltic一medium一acidic Volcanic lava. By rock assem-blage , rock fabric, rock chemical Variction and spatial relationship , the formation isdivided intoupper and lower part,the Primary rock types in each Part basalt一rhyolite from the bottom totop , nevertheless,the upper one concentrate high SiO_2 and alkaline(K_2O+Na_2O).So the upperPart is the Same to Enater Type Volcanic lava and the Lower one alikesto Yellowstone ParkType.