The Early Paleozoic history of the Cuyania (greater Precordillera) terrane of western Argentina: evidence from geochronology of detrital zircons from Middle Cambrian sandstones
The Early Paleozoic history of the Cuyania (greater Precordillera) terrane of western Argentina: evidence from geochronology of detrital zircons from Middle Cambrian sandstones
复制标题
阿根廷西部 Cuyania（大 Precordillera）地体的早古生代历史：来自中寒武统砂岩碎屑锆石地质年代学的证据
DOI：
10.1344/105.000001384
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发表时间：
2005
期刊：
影响因子：
1.5
通讯作者：
K. Marsaglia
中科院分区：
文献类型：
--
作者：
S. Finney;S. Peralta;G. Gehrels;K. Marsaglia
大量碎屑锆石U-Pb年代学是解释砂岩物源的有力工具。这里，将其应用于阿根廷前寒武纪的三种中寒武世砂岩，目的是利用物源解释来检验为Cuyania或Precordillera地体提出的古地理和古构造模型。La Laja组的两个样品具有独特的碎屑锆石年龄分布。所有的锆石颗粒都在1688-1200 Ma和1559-1316 Ma的单峰群内。在这些颗粒中，23%和65%分别位于北美岩浆缺口(1610-1490 Ma)的年龄范围内，表明它们来自非劳伦斯源区。从埃斯坦西亚圣伊西德罗组内一大片石灰岩中的砂岩段采集到的样品截然不同。其锆石群以615-511 Ma的单一年龄群为主，表明源区为布拉西利亚诺造山带。格勒维利亚年龄(1200~950 Ma)的锆石的缺失很难与古地理和大地构造模式相吻合，在古地理和大地构造模式中，Cuyania在寒武纪或奥陶纪从劳伦西亚裂解。这些数据与Cuyania从西冈瓦那南缘分裂出来的模型最一致。考虑到寒武纪与冈瓦那的关系以及后奥陶纪到达冈瓦那现在的位置，Cuyania地体一定是在奥陶纪期间沿着冈瓦那的南部和西部边缘迁移的。
U-Pb geochronology of large detrital zircons populations is a powerful tool for interpreting sandstone provenance. Here, it is applied to three Middle Cambrian sandstones from the Precordillera of Argentina with the purpose of using the provenance interpretations to test paleogeographic and paleotectonic models proposed for the Cuyania or Precordillera terrane. Two samples from the La Laja Formation have distinctive detrital zircon age distributions. All zircon grains fall within unimodal populations of 1688-1200 Ma in one sample and 1559- 1316 Ma in the other. Of these grains, 23% and 65%, respectively, are within the age range of the North American magmatic gap (1610-1490 Ma), indicating a non-Laurentian provenance. A very different sample was taken from a sandstone interval in a large olistolith within the Estancia San Isidro Formation. Its zircon population is dominated by a single, prominent 615-511 Ma age cluster, which is indicative of a provenance in a Brasiliano orogenic belt. The absence of zircons with Grenvillian ages (1200 to 950 Ma) is difficult to reconcile with paleogeographic and geotectonic models in which Cuyania rifted from Laurentia in Cambrian or Ordovician time. The data are most consistent with models in which Cuyania rifted from the southern margin of West Gondwana. Given a Cambrian association with Gondwana and a post-Ordovician arrival at its present position in Gondwana, the Cuyania terrane must have migrated along the southern and western margins of Gondwana during the Ordovician Period.