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在利用成象测井资料准确地恢复岩心空间位置的基础上,建立了位于江苏省东海县毛北村的中国大陆科学钻探主孔岩心1200m精细构造柱。划分了由榴辉岩与超镁铁质岩组成的第一岩性-构造单元及由副片麻岩夹榴辉岩与超镁铁质岩透镜体组成的第二岩性-构造单元,自上而下岩石的面理产状由向东陡倾变为向南东缓倾。第一岩性-构造单元的榴辉岩与超镁铁质岩是毛北榴辉岩杂岩体的组成部分,在榴辉岩中发现以南北向拉伸线理及由北往南的剪切指向为特征的超高压变质岩早期变形举止。位于第二岩性-构造单元下部(770-1130m深度)300多米厚的韧性剪切带是地表出露的毛北韧性剪切带在孔下的延伸,剪切应变及石英组构分析表明,在伴随的退变质角闪岩相→绿帘角闪岩相→绿片岩相的转换过程中,剪切应变由自SE往NW的“逆冲”转为NW向SE的正向滑移。结合钻孔围区地质,重塑了上部由毛北榴辉岩杂岩体与副片麻岩围岩组成的轴面向SE倾斜的同斜倒转褶皱系,以及下部为韧性剪切带的构造模型。钻孔验证了VSP地震反射剖面中850- 12000m深度的强反射层与韧性剪切带相吻合。结合苏鲁超高压变质地体的折返构造的研究,提出该构造模型的成因与折返阶 段超高压变质地体的斜向上的挤出及后折返阶段的穹隆形成有关。
Based on the accurate recovery of the spatial location of core using imaging logging data, a 1200m fine structural column of the core hole of the Chinese mainland scientific drilling located in Mao Beicun, Donghai County, Jiangsu Province was established. The first lithologic-tectonic unit composed of eclogites and ultramafic rocks and the second lithologic-tectonic unit composed of eclogite and ultramafic lenses are distinguished from The topography of the rock from the east to the east steep dumping toward the south easterly. Eclogites and ultramafic rocks of the first lithologic-tectonic unit are part of the Maobei eclogite complex. In the eclogites, the north-south stretching lineage and the shear direction from north to south are found As the characteristics of the early deformation of ultrahigh-pressure metamorphic rocks. The ductile shear zone located 300 m thick in the lower part of the second lithologic-tectonic unit (770-1130 m depth) is an extension of the exposed northern Maobei ductile shear zone under the pore. The shear strain and the quartz structure analysis show that, During the conversion of the extrusive amphibolite facies → chlorite amphibolite facies → greenschist facies, the shear strain changes from “thrusting” from SE to NW to a positive slip of NW to SE. Combined with the geology of borehole enclave, the synclinal inversion fold system of axis-oriented SE and the tectonic model of lower ductile shear zone are reshaped in the upper part by the maobei eclogite complex and the paragneiss. Drilling verified that the strong reflector at 850-12000 m in the VSP seismic reflection profile is consistent with the ductile shear zone. Based on the study of the foldback structure of the ultra-high-pressure metamorphic terrain in Sulu, it is proposed that the genesis of the structural model is related to the diagonal extrusion of the UHP metamorphic terrane and the dome formation at the later reenforcement stage.