Dating granulite-facies structures and the exhumation of lower crust in the Moldanubian Zone of the Bohemian Massif
Dating granulite-facies structures and the exhumation of lower crust in the Moldanubian Zone of the Bohemian Massif
复制标题
波希米亚地块摩尔达努比亚带麻粒岩相结构测年和下地壳折返
DOI：
10.1007/s00531-001-0230-2
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发表时间：
2002
影响因子：
2.3
通讯作者：
Z. Venera
中科院分区：
文献类型：
--
作者：
M. Svojtka;J. Košler;Z. Venera
南波西米亚地块莫尔多瑙河带麻粒岩相岩的变形表现为两个相交的平面构造——陡坡构造（S1）和平缓构造（S2），对应两个变形阶段（D1）和（D2）。条带麻粒岩片麻岩中现有的Sm-Nd石榴石年龄、麻粒岩片麻岩中变形花岗岩侵入体中新的U-Pb锆石数据以及P-T和场结构关系约束了两个变形阶段的年龄和P-T条件。早期变形（D1）与HP-HT变质阶段有关，最小年龄约为354 Ma，随后是近等温减压。U-Pb锆石年龄为318±1 Ma，确定了变形花岗岩侵入麻粒岩片麻岩的时间，并限制了变形阶段（D2）。这一阶段与该地区约340-330 Ma的LP-HT变质作用有关。现有的构造和同位素资料表明，南波西米亚地块的麻粒岩是在挤压过程中由下地壳向中地壳发掘出来的。麻粒岩的构造关系和P-T-t数据与软造山根的近垂直挤压作用相一致。
Deformation of granulite-facies rocks in the Moldanubian Zone of the southern Bohemian Massif is expressed in two intersecting planar fabrics – steeply disposed (S1) and flat-laying (S2) – which correspond to two deformation stages (D1) and (D2). The existing Sm-Nd garnet ages from banded granulite gneisses, new U-Pb zircon data from deformed granite intrusions within the granulite gneisses, and the P–T and field structural relations constrain the ages and P–T conditions of the two deformation phases. The early deformation (D1) was associated with a HP-HT metamorphic stage with a minimum age of ca. 354 Ma which was followed by a near-isothermal decompression. A concordant U-Pb zircon age of 318±1 Ma dates the emplacement of intrusions of deformed granite into the granulite gneisses and constrains deformation phase (D2). This phase was associated with an LP–HT metamorphism dated in the region at ca. 340–330 Ma. The available structural and isotopic data indicate that granulites in the southern Bohemian Massif were exhumed from lower to middle crust during compression. The structural relations and P–T–t data for the studied granulites are consistent with their exhumation by near-vertical extrusion of the softened orogenic root.