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首页> 外文期刊>International Geology Review >Mesoproterozoic Oaxaquia-type basement in peri-Gondwanan terranes of Mexico, the Appalachians, and Europe: T_(DM) age constraints on extent and significance
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Mesoproterozoic Oaxaquia-type basement in peri-Gondwanan terranes of Mexico, the Appalachians, and Europe: T_(DM) age constraints on extent and significance

机译：墨西哥，阿巴拉契亚及欧洲贡多瓦南近地中元古代的Oaxaquia型基底：T_（DM）年龄限制的程度和重要性

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摘要

The basement of most peri-Gondwanan terranes in Mexico, the Appalachians, the Calcdonides, and the Variscidcs is buried beneath younger Ediacaran arc, Palaeozoic passive margin, and/or Mesozoic-Cenozoic platformal carbonates. However, it is exposed in the Oaxaquia terrane of Mexico (Oaxacan, Novillo, Huiznopala, and Guichicovi complexes), where it is characterized by ca. 1.0-1.3 billion yearprotolith ages and igneous rocks with depleted mantle model ages (T_(DM)) of 1.35-1.77 billion years. The T_(DM) ages represent a bulk average composition of the source and can be used as a tracer: these T_(DM) ages overlap with those in ca. 546 Ma arc clasts from the 65.5 Ma Chicxulub bolide breccia, suggesting that the northern Maya block is also underlain by Oaxaquia-type basement. Similar T_(DM) ages occur in Ediacaran arc rocks in Suwannee (Florida), NW Avalonia, Ganderia, Iberia, Armorica, and Bohemia, and in lower Palaeozoic plutons cutting adjacent Palaeozoic passive margin rocks (Acatlan Complex, Gander Group), suggesting that Oaxaquia-type basement underlies these regions. These T_(DM) ages are intermediate between those of SE Avalonia/Carolinia (0.75-1.1 billion years) and the ca. 2.0 Ga basement typical of NW Africa and the Channel Islands of the United Kingdom. The lateral extent of this Oaxaquia-type basement suggests that it formed a Precambrian rim around the periphery of northern Gondwana (Amazonia and NW Africa). The Oaxaquia-type basement beneath Ganderia and northwestern Avalonia suggests that these terranes were derived from the Oaxaquia margin of Amazonia. The polarity of the T_(DM) ages in Avalonia (younger to the SE) suggests that, rather than being transferred orthogonally across Iapetus, these peri-Gondwanan terranes rotated clockwise through ~90° before accretion to Laurentia.
机译：墨西哥大部分冈多瓦南地层，阿巴拉契亚山脉，Calcdonides和Variscidcs的地下埋藏在较年轻的Ediacaran弧，古生代被动边缘和/或中生代-新生代平台碳酸盐岩之下。但是，它暴露于墨西哥的Oaxaquia地貌（Oaxacan，Novillo，Huiznopala和Guichicovi配合物），其特征为大约。 1.0-13亿年的原生石年龄和火成岩的地幔模型年龄（T_（DM））为1.35-17.7亿年。 T_（DM）年龄代表了来源的总体平均构成，可以用作示踪剂：这些T_（DM）年龄与大约3年中的年龄重叠。 546 Ma弧碎屑来自65.5 Ma Chicxulub硼化物角砾岩，表明北部Maya地块也位于Oaxaquia型基底之下。相似的T_（DM）年龄发生在Suwannee（佛罗里达），西北阿瓦龙尼亚，Ganderia，Iberia，Armorica和Bohemia的Ediacaran弧岩中，以及在下古生界岩体中切割相邻的古生界被动边缘岩石（Acatlan Complex，Gander Group）。瓦哈基亚型地下室是这些区域的基础。这些T_（DM）年龄介于SE Avalonia / Carolinia（0.75-11亿年）和ca.非洲西北部和联合王国海峡群岛典型的2.0 Ga地下室。该Oaxaquia型地下室的横向范围表明，它在冈瓦纳北部（亚马逊和西北非洲）的外围形成了前寒武纪边缘。甘德里亚（Ganderia）和西北阿瓦隆（Avalonia）西北部的瓦哈基亚（Oaxaquia）型基底表明，这些地层是源自亚马逊河的瓦哈基亚边缘。 Avalonia（比SE更年轻）的T_（DM）年龄极性表明，这些Gondwanan周边山脉不是在Iapetus上进行正交转移，而是顺时针旋转了约90°，然后才增加到Laurentia。

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