1.3–0.9Ga Oaxaquia (Mexico): Remnant of an arc/backarc on the northern margin of Amazonia
1.3–0.9Ga Oaxaquia (Mexico): Remnant of an arc/backarc on the northern margin of Amazonia
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DOI：
10.1016/j.jsames.2009.07.001
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发表时间：
2010
影响因子：
1.8
通讯作者：
J. Keppie;F. Ortega-Gutiérrez
中科院分区：
文献类型：
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作者：
J. Keppie;F. Ortega-Gutiérrez
年龄约为1Ga的岩石以嵌入体的形式出现在墨西哥中部和南部，周围环绕着无处不在的中、新生代岩石。它们似乎具有共同的历史，包括：(I)约1300-1200 Ma的弧岩浆作用和包括蒸发岩在内的沉积物的沉积；(Ii)约1160-1100 Ma的正长岩、花岗岩和斜长岩的侵入，其后期与混合岩化作用同步；(Iii)约1035-10 Ma的斜长岩-辉长岩-查诺基岩-花岗岩(AMCG)套的侵入；(Iv)1000-980 Ma的麻粒岩相构造热事件，其伸展轴线平行于瓦哈金的长轴；(V)750 Ma和/或545 Ma的逐渐折返；以及(Vi)517 Ma的孤立的钙碱性花岗岩-花岗岩侵入岩。这些露头的共同前寒武纪地质记录表明，它们属于单一地体(瓦哈奎亚)，形成了一个年轻的弧/弧后，与大陆接壤，在1000-980 Ma与阿瓦隆弧发生碰撞和推覆。这埋藏了瓦哈奎亚25-30公里，随后在约917 Ma发生了进一步的超俯冲带岩浆作用。这些前寒武纪岩石不整合地被最上层的寒武纪和志留纪台地岩覆盖，其中包含冈德瓦南动物群和大约1个瓦哈卡源的碎屑锆石。邻近的Mixteca地体包括下古生界裂谷被动边缘沉积岩，其中还含有900-750 Ma的碎屑锆石，可能来自亚马逊东部的GoiáS弧。对1300-900 Ma岩石推断的弧-弧后构造环境也表明，瓦哈克半岛一直位于亚马逊山脉的活动外围，直到大约900 Ma，也就是罗迪尼亚合并之后很久。这排除了瓦哈奎亚位于亚马孙山脉南部和西部之外的位置，据推测，这些地区与东部劳伦西亚并列；鉴于戈阿·S弧内没有900-750 Ma的会聚构造，因此也不太可能与亚马逊东部毗连。这使得亚马孙北部成为最有可能的位置，这个位置需要瓦哈奎亚和亚马逊之间最小的相对位移。推测的瓦哈奎亚750 Ma和545 Ma折返幕对应于罗迪尼亚的两个解体阶段。
Rocks with ages of ca. 1Ga occur in central and southern Mexico as inliers surrounded by ubiquitous Mesozoic and Cenozoic rocks. They appear to share a common history consisting of: (i) ca. 1300–1200Ma arc magmatism and deposition of sediments including evaporites; (ii) ca.1160–1100Ma intrusion of syenite, granite and anorthosite, the later part of which is synchronous with migmatization; (iii) intrusion of a ca. 1035–1010Ma anorthosite–gabbro–charnockite–granite (AMCG) suite; (iv) a 1000–980Ma granulite facies tectonothermal event with a stretching axis parallel to the long axis of Oaxaquia; (v) gradual exhumation at 750 and/or 545Ma; and (vi) 517Ma intrusion of an isolated calcalkaline granitoid pluton. The common Precambrian geological record of these outcrops suggests that they belonged to a single terrane (Oaxaquia) and formed a juvenile arc/backarc bordering a continent that underwent collision with, and overthrusting of, the Avalonian arc at 1000–980Ma. This buried Oaxaquia to 25–30km and was followed by further supra-subduction zone magmatism at ca. 917Ma. These Precambrian rocks are unconformably overlain by uppermost Cambrian and Silurian platform rocks containing Gondwanan fauna and ca. 1 detrital zircons of Oaxacan provenance. The neighbouring Mixteca terrane includes lower Paleozoic, rift-passive margin sedimentary rocks that also contain 900–750Ma detrital zircons probably derived from the Goiás arc in eastern Amazonia. The arc-backarc tectonic setting inferred for the 1300–900Ma rocks also suggests that Oaxaquia lay on an active periphery of Amazonia until ca. 900Ma, well after the amalgamation of Rodinia. This precludes a location for Oaxaquia off southern and western Amazonia that are inferred to have been juxtaposed against eastern Laurentia; contiguity with eastern Amazonia is also unlikely given the absence of the 900–750Ma convergent tectonics in the Goiás arc. This leaves northern Amazonia as the most likely position, a location that requires the least relative displacement between Oaxaquia and Amazonia. The inferred 750 and 545Ma exhumation episodes of Oaxaquia correspond to two proposed breakup stages of Rodinia.