东南极拉斯曼丘陵麻粒岩相岩石中早期残留矿物组合的特征及其变质作用条件  

Characteristics of the Early Remnant Mineral Associations in Granulite facies Rocks from the Larsemann Hills, East Antarctica and Their Metamorphic Conditions

作　　者：仝来喜[1,2] 刘小汉[1,2] 张连生[1,2] 陈海泓 任留东[1,2] 王彦斌 赵越 

机构地区：[1]中国科学院地质研究所 [2]中国地质科学院地质研究所

出　　处：《岩石学报》1997年第2期127-138,共12页Acta Petrologica Sinica

基　　金：国家自然科学基金

摘　　要：东南极拉斯曼丘陵出露的麻粒岩相泥质片麻岩和镁铁质麻粒岩经历了复杂的变形变质历史。代表前进的增厚事件的早期残留变质构造Ｄ１形成于１０００Ｍａ（Ｇｒｅｎｖｉｌｉａｎ）期间。对应于Ｄ１的变质峰期Ｍ１的变质组合以泥质片麻岩的石榴石和尖晶石变斑晶中的堇青石和夕线石包裹体以及镁铁质麻粒岩的石榴石变斑晶中的斜方辉石和斜长石包裹体为特征。在该区斯托尼斯半岛的紫苏黑云石英岩的粗粒紫苏辉石中发现了包裹的假蓝宝石＋磁铁矿和假蓝宝石＋尖晶石＋夕线石＋磁铁矿＋石英组合，这种假蓝宝石又包裹更细粒的尖晶石包裹体。石榴石－斜方辉石温度计及石榴石－斜方辉石－斜长石－石英压力计的计算表明Ｍ１变质作用最大的Ｐ－Ｔ条件为０．９５ＧＰａ和８７０℃。这些早期残留的矿物组合指示了其变质作用具有逆时针近等压冷却（ＩＢＣ）的Ｐ－Ｔ演化特征，反映了它们的形成是一个埋深期间前进加热的进变质作用过程。本文得出该区Ｍ１（１０００Ｍａ）变质作用的逆时针（ＩＢＣ）Ｐ－Ｔ轨迹可能与已存在的大陆壳下面的岩浆底侵作用及地壳内大量岩浆物质的侵入和结晶作用有关。Granulite facies pelitic gneiss and mafic granulite outcropping in the Larsemann Hills, East Antarctica, underwent a complicated deformational metamorphic history. Early remnant D 1 structures represent a prograde thickening event which probably formed at 1000Ma (Grenvillian). In response to D 1, M 1 peak metamorphic assemblages were characterized by inclusions of cordierite and sillimanite within coarse grained garnets or spinels in pelitic gneisses and inclusions of orthopyroxene and plagioclase within coarse grained garnet in mafic granulites. Sapphirine magnetite and sapphirine spinel sillimanite magnetite quartz assemblages included in coarse grained orthopyroxene in orthopyroxene biotite bearing quartzite from Stornes Peninsula have been found, whilst fine grained spinel occurs as inclusions within this sapphirine. P T calculations suggest maximum M 1 metamorphic conditions of ￣870℃ and ￣0.95GPa according to garnet orthopyroxene thermometer and garnet orthopyroxene plagioclase quartz barometer. These remnant mineral associations indicate that their metamorphism takes on characteristics of anticlockwise near isobaric cooling (IBC) P T evolution, also reflect a prograde metamorphic formation process of prograde heating during burial. The M 1 (1000Ma) anticlockwise (IBC) P T path derived here for this area may be related to magmatic underplating beneath existing continental crust and intrusion and crystallization of substantial volumes of igneous material within crust. This type of anticlockwise P T path is distinct from the late clockwise P T path evolved during the 500Ma (Pan African).

关 键 词：麻粒岩 麻粒岩相岩石 残留矿物组合 变质作用 

分 类 号：P588.346[天文地球—岩石学]