Collaborative Research: Tectonothermal History of the Acatlán Complex, Southern Mexico: A Record of the Closure of the Rheic Ocean?

合作研究：墨西哥南部阿卡特兰杂岩的构造热历史：瑞克洋闭合的记录？

• 批准号: 0456180
• 负责人: Brent Miller
• 金额: $ 6.14万
• 依托单位: Texas A&M Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-10-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0456180&HistoricalAwards=false
• 关键词: Collaborative; Research; Tectonothermal; History; Acatl

AbstractThe well-exposed Acatlan Complex of southern Mexico records the closure of a major Paleozoic ocean. Exposing Mexico's largest area of Paleozoic geology (27,500 km2 ), the complex comprises an assemblage of repeatedly deformed clastic metasedimentary sequences, locally eclogite-facies mafic-ultramafic suites, and arc-related granitoid bodies that together record a protracted history of Paleozoic orogenesis. Juxtaposed against granulite facies gneisses of late Mesoproterozoic age with an Amazonian affinity (the Oaxacan Complex), the nature of the tectonostratigraphic record of the Acatlan Complex is not only central to the accretionary history of Mexico, but also bears upon wider issues of Paleozoic continental reconstructions. Despite its importance, however, a targeted structural-geochronological study of the complex of the type needed to unravel its tectonic history has yet to be undertaken. As a result, significant aspects of its geologic evolution are uncertain and existing models for its tectonic development are in conflict. Thus, the age and number of tectonothermal events the complex records are uncertain, key aspects of its kinematic history are unknown, its initial deformation has been variably correlated with the Taconic, Salinic and Acadian events of the Appalachians, and its evolution has been attributed to closure of both the Iapetus and Rheic oceans. To help resolve these controversies and clarify the complex's tectonic history, The PI's propose to conduct an investigation that combines detailed field mapping, structural-kinematic analysis and geochemistry with precise laserprobe 40 Ar/ 39 Ar, conventional U-Pb and ion-microprobe age dating. The investigation will use a targeted approach aimed at determining (1) the precise age, inheritance and kinematic significance of the complex's granitoid bodies, (2) the depositional age, provenance and tectonothermal history of its metasedimentary sequences, and (3) the precise age and tectonothermal evolution of its mafic-ultramafic units. These data are essential to understanding the tectonic history of the complex and will be used to establish its role in Mexico's accretionary history and to evaluate its linkages to the Appalachians.Intellectual Merit: Structural-kinematic analysis in combination with geochemical fingerprinting and precise geochronology provides a powerful tool for unraveling the tectonic history of regions of complex geology. The proposed project will greatly clarify the evolution of this important Paleozoic terrane and, in so doing, provide new insight into key aspects of the Paleozoic accretionary history of Mexico, its relationship to the development of the Appalachians, and its role in Laurentia-Amazonia connections for the Neoproterozoic and Paleozoic. Broader Impact: Preliminary analysis of the tectonostratigraphic record of the Acatlan Complex coupled with its close association with the late Mesoproterozoic Oaxacan Complex, the Paleozoic cover of which contains fossils of Gondwanan affinity, suggests that the complex records the closure of the Rheic Ocean. If so, its tectonothermal evolution promises new insight into the history of this important but poorly understood ocean, the closure of which produced the climactic Ouachita-Alleghenian-Variscan collision between Gondwana and Laurussia during the assembly of Pangea. The project also represents an international collaboration between the United States and Mexico that will promote joint research and educational partnerships and provide both undergraduate and graduate students with unique opportunities for research and international exchange.

墨西哥南部的阿卡特兰复合体（Acatlan Complex）暴露良好，记录了一个主要古生代海洋的闭合。暴露墨西哥最大面积的古生代地质（27,500平方公里），复杂的组合包括反复变形的碎屑变质沉积序列，局部榴辉岩相镁铁质-超镁铁质套房，以及弧相关的花岗岩类岩体，共同记录了古生代造山作用的漫长历史。与中元古代晚期的麻粒岩相片麻岩（具有亚马逊河的亲和力）并列，Acatlan杂岩的构造地层记录的性质不仅是墨西哥加积历史的核心，而且也关系到古生代大陆重建的更广泛的问题。然而，尽管其重要性，尚未进行有针对性的结构-地质年代学研究，以揭示其构造历史所需的复杂类型。因此，其地质演化的重要方面是不确定的，其构造发展的现有模型相互冲突。因此，复杂记录的构造事件的年龄和数量是不确定的，它的运动历史的关键方面是未知的，它的初始变形已与阿巴拉契亚山脉的塔康尼克，Salinic和Escherdian事件相关，它的演变归因于Iapetus和Rheic海洋的关闭。为了帮助解决这些争议并澄清复杂的构造历史，PI建议进行一项调查，将详细的野外测绘，结构运动学分析和地球化学与精确的激光探针40 Ar/ 39 Ar，常规U-Pb和离子微探针年龄测定相结合。调查将采用有针对性的方法，旨在确定（1）杂岩体的花岗岩体的精确年龄、继承性和运动学意义，（2）其变质沉积序列的沉积年龄、物源和构造历史，以及（3）其镁铁质-超镁铁质单元的精确年龄和构造演化。这些数据是必不可少的复杂的构造历史的理解，并将被用来建立其在墨西哥的增生历史的作用，并评估其与阿巴拉契亚山脉的联系。智力优点：结合地球化学指纹和精确的地质年代学结构运动学分析提供了一个强大的工具，解开地质复杂的地区的构造历史。拟议的项目将大大澄清这一重要的古生代沉积物的演变，并在这样做，提供新的见解墨西哥古生代增生历史的关键方面，其关系的阿巴拉契亚山脉的发展，其作用在劳伦蒂亚-亚马逊连接新元古代和古生代。更广泛的影响：对阿卡特兰杂岩的构造地层记录的初步分析，加上其与晚中元古代瓦哈坎杂岩的密切联系，其古生代盖层含有冈瓦纳亲缘关系的化石，表明该杂岩记录了莱茵洋的闭合。如果是这样的话，它的构造演化有望对这一重要但知之甚少的海洋的历史有新的见解，在泛大陆的组装期间，这一海洋的闭合产生了冈瓦纳和劳鲁西亚之间的高潮Ouachita-Alleghenian-Variscan碰撞。该项目还代表了美国和墨西哥之间的国际合作，将促进联合研究和教育伙伴关系，并为本科生和研究生提供独特的研究和国际交流机会。