The Pacific Gondwana margin in the late Neoproterozoic-early Paleozoic: Detrital zircon U-Pb ages from metasediments in northwest Argentina reveal their maximum age, provenance and tectonic setting
The Pacific Gondwana margin in the late Neoproterozoic-early Paleozoic: Detrital zircon U-Pb ages from metasediments in northwest Argentina reveal their maximum age, provenance and tectonic setting
复制标题
DOI：
10.1016/j.gr.2010.05.002
复制
发表时间：
2011-01-01
影响因子：
6.1
通讯作者：
Griffin, W. L.
中科院分区：
文献类型：
--
作者：
Adams, C. J.;Miller, H.;Griffin, W. L.
报道了Puncoviscana组碎屑锆石U-Pb年龄（新元古代晚期-早寒武世）和介子群新的数据与以前发表的碎屑锆石年龄相结合，表明Puncoviscana组的年龄模式包含两大组：中元古代晚期-新元古代早期（1150850 Ma）和新元古代晚期-早寒武世（650-520 Ma），其相对比例与最年轻组分年龄成反比。灰岩以1150-850 Ma年龄组份为主，最古老的晚新元古代年龄组份>600 Ma。前者大大减少时，新元古代晚期组件成为主导和年轻，520马。最北端的杂砂岩样品来自胡胡伊，是独特的：虽然它的锆石年龄模式部分类似于其他Puncoviscana组样品，它不包含寒武纪晚新元古代的年龄，最年轻的年龄是新元古代早期。这可能反映了一个早期的新元古代被动边缘沉积中心的形成，或一个更老的（新元古代早期）继承它，这可能早于巴西的Brasiliano orthodox。最年轻的年龄组，C。520马，从Rancagua（卡奇，萨尔塔省）的杂砂岩，占主导地位的几乎单峰模式暗示当代火山源在晚寒武世沉积中心。介子群（Lizoite组）的碎屑锆石年龄模式具有类似于Puncoviscana组的寒武纪-新元古代晚期的主要成分，但其中元古代成分减少，并且该年龄没有显著的年龄成分。最年轻的C。500 Ma的最大地层年龄为晚寒武世。Puncoviscana组碎屑锆石的模式表明，在大陆腹地有一个稳定的，广泛的晚中元古代造山带（与小古元古代和太古代前体），和一个更可变的晚新元古代造山带包含一个不断变化的序列不太广泛的子组件的起源。与巴西地盾的直接关系，建议与沉积物供应内的内部和碰撞造山带在缝合线之间的非洲和南美洲的大陆，但最终沉积在冈瓦纳大陆西部的被动边缘环境的主动边缘造山带。(C)2010年国际冈瓦纳研究协会。Elsevier B. V.出版，保留所有权利。
U-Pb detrital zircon ages are reported from Puncoviscana Formation (late Neoproterozoic-Early Cambrian) and Meson Group (Late Cambrian) greywackes of northwest Argentina, to constrain provenance and depositional environment.The new data are combined with previously-published detrital zircon ages, to show that Puncoviscana Formation age patterns contain two broad groups: late Mesoproterozoic-early Neoproterozoic (1150850 Ma) and late Neoproterozoic-Early Cambrian (650-520 Ma); with their relative proportions varying inversely with youngest component age. The 1150-850 Ma age components are dominant in greywackes with oldest late Neoproterozoic components >600 Ma. The former diminish considerably when late Neoproteozoic components become dominant and younger, to 520 Ma. A northernmost greywacke sample from Purmamarca, Jujuy, is distinctive: whilst its zircon age pattern partly resembles other Puncoviscana Formation samples, it contains no Cambrian-late Neoproterozoic ages, the youngest ages being early Neoproterozoic. This may reflect an early, Neoproterozoic, passive-margin depocentre for the Formation, or an older (early Neoproterozoic) succession within it, which may predate the Brasiliano orogeny in Brazil. The youngest age components, c. 520 Ma, in a greywacke from Rancagua (Cachi, Salta province), dominate an almost unimodal pattern suggestive of contemporary volcanic sources at a late Early Cambrian depocentre. Detrital zircon age patterns of the Meson Group (Lizoite Formation) have major Cambrian-latest Neoproterozoic components resembling those of the Puncoviscana Formation, but its Mesoproterozoic component is diminished, and there are no significant age components of this age. Small youngest components at c. 500 Ma suggest a maximum Late Cambrian stratigraphic age. The Puncoviscana Formation detrital zircon patterns suggest a provenance in a continental hinterland having a stabilised, extensive late Mesoproterozoic orogen (with minor Paleoproterozoic and Archean precursors), and a more variable late Neoproterozoic orogen containing an evolving sequence of less extensive subcomponents. A direct relationship with the Brazilian Shield is suggested; with sediment supplies originating within active-margin orogens of the interior and collisional orogens at the suture between African and South American cratons, but ultimate deposition in passive-margin environments of western Gondwanaland. (C) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.