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首页> 外文期刊>Gondwana research: international geoscience journal >Cuyania, an exotic block to Gondwana: Review of a historical success and the present problems
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Cuyania, an exotic block to Gondwana: Review of a historical success and the present problems

机译：Cuyania，冈瓦纳的异国情调街区：回顾历史上的成功和当前的问题

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摘要

A review of the early history of the Cuyania terrane and the numerous pioneering works of the past century provides the present robust framework of evidence supporting a derivation from Laurentia, travel towards Gondwana as an isolated microcontinent, and final amalgamation to the protomargin of western Gondwana in Middle to Late Ordovician times. The major remaining uncertainties and inconsistencies, such as the time of deformation and collision with Gondwana, the lack of evidence of Famatinian-derived zircons, the effects of strike-slip displacements proposed along the suture, as well as the potential sutures defined by ophiolite assemblages, are discussed. The precise boundary along the northern and southern limits is not yet well defined. The most suitable hypothesis based on present data is that Cuyania originated as a conjugate margin of the Ouachita embayment, south of the Appalachian platform during Early Cambrian times. The subsequent travel toward the Gondwana protomargin is clearly depicted by the changing faunal assemblages in the carbonate platform. New geochemical and age data on K-bentonites presented by several authors reinforce the strong connection between Cuyania ash-fall tuffs and Famatina volcanics by 468-470 Ma, indicating Cuyania and Gondwana were in close proximity at that time. Extension related to flexural subsidence, preceded by the drowning of the carbonate platform in early Llanvirnian times, is recorded by abrupt facies changes in the sedimentary cover during late Llanvirnian and early Caradocian times. This episode marked the beginning of contact between Cuyania and Gondwana. The subsequent evolution of the foreland basin indicates that deformation lasted until latest Silurian-Early Devonian times. The time of collision is tracked by the cessation of arc-related magmatic activity in the upper plate (Gondwana protomargin), at about 465 Main western Sierras Pampeanas, and ages around 454 Ma corresponding to syncollisional and postcollisional magmatism. The age of the collision is also preserved in the lower plate (Cuyania), where both angular unconformities in the sedimentary cover and the ages of peak of regional metamorphism in the basement rocks point to 460 Ma as the most probable age for the beginning of the collision. Evidence from the upper plate is essentially identical with an age of 463 Ma. Thermal gradients along this suture vary from 13 degreesC/km in the lower plate, to 18 degreesC/km in the fore arc upper plate, reaching more than 30 degreesC/km along the Famatinian arc. Based on these data, a Llandelian-Caradocian age for the collision can be postulated on firm grounds. Deformation continued through most of the early Paleozoic until amalgamation of the Chilenia terrane by the Late Devonian.
机译：回顾Cuyania地形的早期历史和上个世纪的众多开创性作品，提供了目前可靠的证据框架，支持从Laurentia衍生，作为孤立的微大陆前往Gondwana以及最终合并到Gondwana西部的原边缘。奥陶纪中期至晚期。主要的不确定性和不一致性，例如变形和与冈瓦纳碰撞的时间，缺乏法马汀派锆石的证据，沿缝线提出的走滑位移的影响以及蛇绿岩组合物定义的潜在缝线，进行了讨论。北部和南部边界的精确边界尚未很好定义。根据目前的数据，最合适的假设是，卡亚尼亚起源于寒武纪初期阿巴拉契亚台地以南的瓦奇托河道的共轭边缘。碳酸盐台地中动物群的变化清楚地描绘了随后到达冈瓦纳原边的旅行。几位作者提出的有关钾膨润土的新地球化学和年龄数据加强了卡亚尼亚火山灰凝灰岩与法马蒂纳火山之间468-470 Ma的紧密联系，表明当时卡亚尼亚和冈瓦纳距离很近。在拉尔维尼亚早期，碳酸盐岩平台被淹没之前，与弯曲沉降有关的扩张被拉尔维尼亚晚期和卡拉多西亚早期沉积相的突然相变化所记录。这一事件标志着库亚尼亚和冈瓦纳之间开始接触。前陆盆地的后续演化表明，变形一直持续到志留纪-早泥盆世时期。碰撞时间是由上盘（冈瓦纳原边）中的大约465个主要的西山脉Pampeanas上的弧相关岩浆活动的停止来跟踪的，其年龄在454 Ma左右，对应于成岩和碰撞后的岩浆作用。碰撞的年龄也保留在下板块（卡里亚尼亚）中，沉积覆盖层的角不整合面和基底岩石中区域变质峰的年龄都指向460 Ma，这是该板块开始的最可能年龄。碰撞。上板的证据与463 Ma年龄基本相同。沿着该缝合线的热梯度从下板的13摄氏度/公里变化到前弧上板的18摄氏度/公里，沿法马汀弧达到30摄氏度/公里以上。基于这些数据，可以以坚实的理由推测发生碰撞的兰迪利亚-卡拉多西亚年龄。变形一直持续到整个古生代早期，直到晚泥盆世合并智利地体为止。

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