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大别山中南部分布着约1000余平方公里的超高压变质(UHP)带,可谓世界出露规模最大的造山带超高压变质带.UHP岩石形成与折返机制成为大陆造山带研究热点.目前人们的工作焦点集中于UHP岩石的矿物、地球化学、年代学和变质作用(PTt轨迹),而UHP带内部岩石变形和组成研究相对较少,但已引起重视.作者自1992年在苏北赣榆UHP岩石之下发现“石桥浅变质岩构造窗”后,近年在大别山UHP带又找到了浅变质岩片,并进行露头填图、年代学及组成研究.本文现就其地质特征和年代学的初步成果进行讨论.1 浅变质岩片地质产状与特征作者发现的浅变质岩,位于岳西县菖蒲南4km港河桥(图1).菖蒲是大别山UHP带典型出露区,产出与大理岩的榴辉岩、片麻岩的榴辉岩,以及超基性岩的榴辉岩等不同类型的UHP岩石伴生.在其北约3km为大别山最大的榴辉岩体——碧溪岭岩体(约0.7km~2),这是与石榴橄榄岩伴生的UHP类型,浅变质岩片夹在榴辉岩-片麻岩和榴辉岩-大理岩中,出露宽约80m,长>300m(未控制).岩性为酸性火山碎屑岩和火山沉积岩(板岩),变质程度低,由火山碎屑指示的原生层面依稀可辨,其SiO_2为68.46～72.04,Al_2O_3为18.52～21.56,K_2为O3.25～3.46,Na_2O为1.04～1.18;面理平行接触带,平行UHP带的面理产状,倾向南东(120°～140°/40°).接触带
UHP belt of about 1000 square kilometers is distributed in south-central part of Dabie Mountains, which can be described as the largest orogenic ultrahigh pressure metamorphic belt exposed in the world .UHP rock formation and reentry mechanism has become the hotspot in the mainland orogenic belt. Focusing on the mineralogy, geochemistry, geochronology and metamorphism (PTt trajectory) of UHP rocks, there are relatively few studies on the deformation and composition of UHP rocks within the UHP belt, but attention has been paid to this. Since 1992, After the discovery of the “Shiqiao shallow metamorphic rock structure window”, in recent years, the UHP belt in the Dabie Mountains to find a further metamorphic rock fragments, and outcrop mapping, chronology and composition of the study is on its geological characteristics and chronological preliminary results The shallow metamorphic rock of shallow metamorphic rock is located in the 4km Gangheqiao of Ipomoea in Yuexi County (Fig.1) .The iris is a typical outcrop of the UHP belt in the Dabie Mountains, Eclogites and gneiss eclogites and eclogites of ultramafic rocks are associated with different types of UHP rocks.In the northern part of the country about 3km is the largest eclogite body in the Dabie Mountains, 0.7km ~ 2), this is with Peridotite associated with UHP type, shallow metamorphic rocks are sandwiched between eclogite-gneiss and eclogite-marble, about 80m wide and> 300m long (uncontrolled). Lithology is acidic volcanic debris The rocks and volcanic sedimentary rocks (slate) have a low degree of metamorphism. The primary layers indicated by volcanic debris are vaguely discernible. The SiO 2 is 68.46-72.04, Al 2 O 3 is 18.52-21.56, K 2 is O 3.25- 3.46, Na 2 O is 1.04 ~ 1.18; face parallel to the contact zone, the parallel UHP zone with the appearance of production, the tendency of the south east (120 ° ~ 140 ° / 40 °). Contact zone