南京大学学报(自然科学版) ›› 2011, Vol. 47 ›› Issue (6): 718730.
吴倩怡1.2**
Wu Qian一Yi 1.2
摘要: 大别山碧溪岭超高压榴辉岩主要由石榴石、绿辉石、柯石英/石英、蓝晶石、多硅白云母、金红石、黝帘石、滑石、角闪石组成.含滑石变斑晶的榴辉岩样品中石榴石变斑晶在背散射图像中可观察到深
浅不一的两种色调.深色部分比浅色部分含有更高的Xmg.矿物结构关系显示岩石可能曾经含有硬柱石.峰变质阶段后,随着温度和压力下降,硬柱石分解,形成硬柱石假象(蓝晶石+绿帘石+石英).但是,
这些矿物所构成的结构也可以解释为帘石生长,包围属于峰变质阶段矿物组合的蓝晶石及石英(柯石英).相图计算结果指出这两种可能性对应于不同的P-T路径.浅色榴辉岩中滑石与早期形成的石榴
石、绿辉石一同在榴辉岩变质演化初期己经存在.在经历峰变质阶段后,帘石开始生长.退变质过程进一 步发生,滑石变斑晶生长.利用石榴石一绿辉石一多硅白云母一柯石英温压计计算得到浅色榴辉岩所经
历的峰变质阶段的P-T条件为3. 8 GPa,640ºC.
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