Basement lithostratigraphy of the Adula nappe: implications for Palaeozoic evolution and Alpine kinematics
Basement lithostratigraphy of the Adula nappe: implications for Palaeozoic evolution and Alpine kinematics
复制标题
阿杜拉推覆体的基底岩石地层学：对古生代演化和高山运动学的影响
DOI：
10.1007/s00531-013-0941-1
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发表时间：
2013
影响因子：
2.3
通讯作者：
A. Ulianov
中科院分区：
文献类型：
--
作者：
M. Cavargna;J. Epard;F. Bussy;A. Ulianov
阿杜拉推覆体属于瑞士阿尔卑斯山脉中部的下奔尼尼克地区。它主要由前三叠纪基底岩性组成，表现为各种类型的强烈褶皱和剪切片麻岩，带有基性岩香肠。我们提出了一个新的岩石地层学的北方阿都拉推覆基底，支持详细的实地调查，锆石U-Pb年代学，和全岩地球化学。已识别出以下单元：寒武纪碎屑变质沉积，具有丰富的碳酸盐透镜体和少量双峰式岩浆活动（Salahorn组）;与角闪岩石香肠有关的奥陶纪变质岩，含有大量代表大洋变质玄武岩的榴辉岩残余物（Trescolmen组）;奥陶系钙碱性亲合的过铝质变花岗岩，归因于俯冲相关的岩浆作用（Garenstock Augengneiss）;奥陶纪变质火山-沉积矿床（Heinisch Stafel Formation）;仅记录阿尔卑斯造山事件的早二叠世后碰撞花岗岩（Zervreila orthogneiss）。除二叠纪花岗岩外，所有基底岩性都记录了华力西-阿尔卑斯多造山变质历史。它们记录了一个复杂的古生代大地构造演化，与阿尔卑斯山前中生代基底框架所提供的更广泛的图景相一致。阿都拉基底岩性的内部一致性和上覆三叠纪沉积物的地层连贯性表明，阿都拉推覆体内的大多数构造接触是前阿尔卑斯山的年龄。因此，阿都拉推覆体第三纪侵位的混杂岩模型并不一致，必须予以拒绝。阿都拉推覆体现今构造的复杂性是一个前构造实体强烈的阿尔卑斯韧性变形的结果。
The Adula nappe belongs to the Lower Penninic domain of the Central Swiss Alps. It consists mostly of pre-Triassic basement lithologies occurring as strongly folded and sheared gneisses of various types with mafic boudins. We propose a new lithostratigraphy for the northern Adula nappe basement that is supported by detailed field investigations, U–Pb zircon geochronology, and whole-rock geochemistry. The following units have been identified: Cambrian clastic metasediments with abundant carbonate lenses and minor bimodal magmatism (Salahorn Formation); Ordovician metapelites associated with amphibolite boudins with abundant eclogite relicts representing oceanic metabasalts (Trescolmen Formation); Ordovician peraluminous metagranites of calc-alkaline affinity ascribed to subduction-related magmatism (Garenstock Augengneiss); Ordovician metamorphic volcanic–sedimentary deposits (Heinisch Stafel Formation); Early Permian post-collisional granites recording only Alpine orogenic events (Zervreila orthogneiss). All basement lithologies except the Permian granites record a Variscan + Alpine polyorogenic metamorphic history. They document a complex Paleozoic geotectonic evolution consistent with the broader picture given by the pre-Mesozoic basement framework in the Alps. The internal consistency of the Adula basement lithologies and the stratigraphic coherence of the overlying Triassic sediments suggest that most tectonic contacts within the Adula nappe are pre-Alpine in age. Consequently, mélange models for the Tertiary emplacement of the Adula nappe are not consistent and must be rejected. The present-day structural complexity of the Adula nappe is the result of the intense Alpine ductile deformation of a pre-structured entity.