Abstract Eclogites are witnesses of geodynamic processes that are commonly related to subduction of oceanic crust. Information on the part of these processes that refers to the burial of this rock type is rarely published but stored in the eclogitic garnet core and inclusions therein. To better understand general aspects of the burial process, a literature search on the chemical characteristics of garnet in worldwide occurrences of eclogite was undertaken. In most cases extended garnet cores show either a prograde growth zoning with increasing Mg, starting at a few percent of pyrope component, and decreasing Mn contents (type I eclogite) or a (nearly) constant chemical composition frequently with pyrope contents significantly above 10 percent (eclogites of types II and III). Only in minor cases, it is difficult to assign the reported garnet core to an eclogite type. The growth zoning of garnet was thermodynamically modelled for the chemical composition of a basalt following different burial paths. These paths are characterized either by a trajectory along a low geothermal gradient (type I eclogite), as expected for the subducting upper portion of oceanic crust, or a one characterized by nearly isothermal burial at temperatures above 500 °C reaching peak pressures up to 2.1 GPa (type III eclogite), as possibly due to crustal thickening during continent-continent collision, or more (type II eclogite) when basic rocks are tectonically eroded from the overriding continental plate before deep subduction. In addition, diffusion modelling was undertaken on mm-sized garnet demonstrating that the characteristics of the core zoning are not fully obliterated even during residence at temperatures of 800-850 °C within 10 million years. The scrutiny of more than 200 eclogites reported in the literature led to the following result: about half of them are type II eclogites; a third and a sixth can be related to type I and type III, respectively. Among type III are almost all of the few Proterozoic eclogites considered. To demonstrate the benefit of our study, we link the core zoning of eclogitic garnet from various (ultra)high-pressure terranes in Phanerozoic orogenic belts to the geodynamics shaping corresponding orogens. The eclogites in these belts are dominated by type II. Thus, we propose that some of the material of the lower portion of the overriding continental crust was tectonically eroded by a subducted oceanic plate and brought to great depth. Afterwards, this material was exhumed first in a deep subduction channel and then in an exhumation channel during continent-continent collision where a contact with the upper continental plate was re-established. Furthermore, we suggest that type II eclogite can also occur in extrusion wedges as far as oblique subduction took place.

中文翻译：

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榴辉岩核的分区 – 一个关键模式，表明构造侵蚀占主导地位，这是世界范围内榴辉岩埋藏过程的一部分

摘要 榴辉岩是地球动力学过程的见证，通常与洋壳俯冲有关。这些过程中涉及这种岩石类型埋藏的部分信息很少公开，但存储在榴辉岩核心和其中的包裹体中。为了更好地了解埋藏过程的一般方面，对世界范围内榴辉岩产地中石榴石的化学特征进行了文献检索。在大多数情况下，扩展的石榴石核显示出随着镁含量增加的顺向生长区带，从几个百分比的镁榴石成分开始，并降低锰含量（I 型榴辉岩）或（几乎）恒定的化学成分，通常镁榴石含量显着高于 10% （II 型和 III 型榴辉岩）。只有在轻微的情况下，很难将报道的石榴石核归为榴辉岩类型。石榴石的生长分区是根据不同埋藏路径的玄武岩的化学成分进行热力学模拟的。这些路径的特征要么是沿着低地温梯度（I 型榴辉岩）的轨迹，如洋壳上部俯冲所预期的那样，要么是在温度高于 500 °C 时接近等温埋藏，峰值压力高达 2.1 GPa（III型榴辉岩），可能是由于大陆-大陆碰撞期间地壳增厚，或者更多（II型榴辉岩），当基性岩石在深俯冲之前从上覆大陆板块构造侵蚀。此外，对毫米大小的石榴石进行了扩散建模，表明即使在 800-850 °C 的温度下停留 1000 万年，核心区带的特征也不会完全消失。对文献报道的200余种榴辉岩进行考察，得出以下结论：其中约一半为II型榴辉岩；第三个和第六个可以分别与 I 型和 III 型相关。几乎所有的少数元古代榴辉岩都属于 III 型。为了证明我们研究的益处，我们将显生宙造山带中各种（超）高压地体的榴辉岩的核心区带与塑造相应造山带的地球动力学联系起来。这些带中榴辉岩以Ⅱ型为主。因此，我们认为，上覆大陆地壳下部的一些物质被俯冲的大洋板块构造侵蚀并带到很深的地方。之后，这些物质首先在深俯冲通道中被挖掘出来，然后在大陆-大陆碰撞期间在一个挖掘通道中被挖掘出来，在那里重新建立了与上大陆板块的接触。此外，我们认为 II 型榴辉岩也可以出现在挤压楔中，就发生倾斜俯冲而言。