摘要
茹尔群岛(又称赖于尔群岛)位于东南极普里兹构造带的东部边缘,是一个由太古宙和中元古代岩石组成的复合高级变质地体。中元古代岩石是含有富Fe-Al的含石榴子石-矽线石的费拉副片麻岩组合,经历了格林维尔和泛非两期变质作用。太古宙正片麻岩是含有富Mg-Al的含假蓝宝石的超高温泥质麻粒岩组合(梅瑟副片麻岩组合),主要由经历超高温变质作用的含假蓝宝石的泥质麻粒岩、富Mg的石榴子石-矽线石泥质片麻岩、斜方辉石-矽线石石英岩、含石榴子石镁铁质麻粒岩和钙硅酸盐麻粒岩等组成。其中,含假蓝宝石泥质麻粒岩中石榴子石变斑晶和矽线石集合体(蓝晶石假象)周围分别发育峰期后由假蓝宝石+斜方辉石和假蓝宝石+堇青石后成合晶组成的典型减压结构。含石榴子石镁铁质麻粒岩中石榴子石变斑晶周围则发育峰期后由斜方辉石+斜长石后成合晶组成的典型白眼圈减压结构。不同研究者得出了具有不同超高温峰期条件、峰期前及峰期后演化历史、不同形式的顺时针变质P-T轨迹。对超高温变质事件发生的时间和构造背景的认识也存在较大分歧,有认为超高温变质事件发生于格林维尔期(~1000 Ma)并与碰撞造山和弧岩浆作用有关,也有研究认为发生于泛非期(~590 Ma或~530 Ma)并与普里兹造山及冈瓦纳大陆聚合有关。因此,为理清该区超高温麻粒岩的变质演化历史和构造背景,需要对其进一步进行详细深入的矿物组合-变质结构分析、P-T轨迹重建及高精度的锆石-独居石U-Pb年代学研究,并进行区域上对比。
The Rauer Group(Rauer Islands),located in the eastern margin of the Prydz Tectonic Belt in East Antarctica,represents a composite high-grade metamorphic terrane consisting of Archaean and Mesoproterozoic rocks.The Mesoproterozoic rocks contain Fe-Al-rich garnet-sillimanite-bearing Filla Paragneiss associations,and have experienced two phases of metamorphism involving Grenvillian and Pan-African events.The Archaean orthogneisses contain Mg-Al-rich sapphirine-bearing ultrahigh-temperature(UHT)pelitic granulite associations(Mather Paragneiss associations),and they consist mainly of sapphirine-bearing pelitic granulite,Mg-rich garnetsillimanite-bearing pelitic paragneiss,orthopyroxene-sillimanite quartzite,garnet-bearing mafic granulite and calcsilicate granulite that experienced ultrahigh-temperature metamorphism.In the sapphirine-bearing pelitic granulite,typical post-peak decompression textures around garnet porphyroblasts and sillimanite aggregations(kyanite pseudomorph)developed as symplectite assemblages consisting of sapphirine-orthopyroxene and sapphirine-cordierite respectively.In the garnet-bearing mafic granulite,typical post-peak‘white-eye socket’decompression texture on garnet porphyroblast also developed as symplectite composed of orthopyroxeneplagioclase.Until recently,different researchers derived distinct-type clockwise P-T paths of various peak UHT conditions and pre-peak and post-peak evolution histories,whereas different opinions also exist regarding the timing of UHT metamorphic event and tectonic setting.For example,a UHT metamorphic event was considered to occur either during the Grenvillian period(~1000 Ma)associated with a collisional orogenesis and arc magmatism or during the Pan-African period(~590 Ma or~530 Ma)related to the Prydz orogenesis and the Gondwana continent assembly.Thus,in order to clarify the metamorphic evolution history and tectonic setting of the UHT granulites in the region,further detailed studies on analyses of the mineral assemblages and metamorphic textures and the reconstruction of P-T path as well as high-precesion zircon and monazite U-Pb chronological dating are needed,and regional geological comparison should also be undertaken.
作者
仝来喜
刘兆
王彦斌
TONG Laixi;LIU Zhao;WANG Yanbin(State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,Shaanxi,China;Institute of Geology,Chinese Academy of Geological Science,Beijing 100037,China)
出处
《地质力学学报》
CSCD
北大核心
2021年第5期705-718,共14页
Journal of Geomechanics
基金
国家自然科学基金项目(41972050,41530209)。
关键词
超高温麻粒岩
变质P-T轨迹
研究进展
茹尔群岛
东南极
ultrahigh-temperature granulites
metamorphic P-T paths
research progress
Rauer Group
East Antarctica
