Mid-Cenozoic SHRIMP U-Pb detrital zircon ages from metasedimentary rocks in the North Patagonian Andes of Aysén, Chile

IF 0.9 4区地球科学 Q3 GEOLOGY

Andean Geology Pub Date : 2021-01-29 DOI:10.5027/ANDGEOV48N1-3282

P. Quezada, F. Hervé, Mauricio Calderón Nettle, C. Fanning, R. Pankhurst, E. Godoy, O. Urbina, R. Suárez

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Abstract

Previously undated low-grade metamorphic rocks from the Puerto Cisnes-Queulat area (44°30’ S) contain detrital zircons of mid-Oligocene age (ca. 28 Ma). Their outcrops represent the easternmost occurrence of the late Oligocene to early Miocene marine volcano-sedimentary Traiguén Formation; previous correlation with the Paleozoic metamorphic basement of this sector of the North Patagonian Andes is thus refuted. A similar age and provenance were obtained for a paraconglomerate bed of the La Junta Formation ca. 80 km to the north, which is thought to represent a high-energy lateral facies variation of the Traiguén Formation. Miocene plutonic rocks of the North Patagonian Batholith intruded these metasedimentary rocks, generating a contact metamorphic aureole that reaches biotite grade and overprints a previous metamorphic fabric probably formed during closure of the Traiguén Basin. Similar young ages for metamorphic rocks located immediately west of the Liquiñe-Ofqui Fault Zone 300 km north, near Ayacara, suggest a regional pattern of earliest Neogene metamorphism and rapid exhumation in this segment of the Patagonian Andes.

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智利ays北巴塔哥尼亚安第斯山脉变质沉积岩中新生代SHRIMP U-Pb碎屑锆石

Puerto Cisnes-Queulat地区(44°30′S)的低变质岩中含有中渐新世(约28 Ma)的碎屑锆石。它们的露头代表晚渐新世至早中新世海相火山-沉积特瑞古萨组最东端的产状;因此，先前与北巴塔哥尼亚安第斯山脉这一段古生代变质基底的对比被反驳。在其北部约80 km处的La Junta组副砾岩层也获得了类似的年龄和物源，认为这代表了traigusamn组的一次高能侧向相变化。北巴塔哥尼亚基中新世深成岩侵入了这些变质沉积岩，形成了黑云母级的接触变质光圈，并覆盖了可能在特拉古桑盆地闭合期间形成的变质构造。位于Liquiñe-Ofqui断裂带以西300公里以北的Ayacara附近的变质岩的相似年龄表明，在巴塔哥尼亚安第斯山脉的这一段，最早的新近纪变质作用和快速挖掘的区域模式。

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来源期刊

Andean Geology 地学-地质学

CiteScore

3.90

自引率

0.00%

发文量

审稿时长

>12 weeks

期刊介绍： This journal publishes original and review articles on geology and related sciences, in Spanish or English, in three issues a year (January, May and September). Articles or notes on major topics of broad interest in Earth Sciences dealing with the geology of South and Central America and Antarctica, and particularly of the Andes, are welcomed. The journal is interested in publishing thematic sets of papers and accepts articles dealing with systematic Paleontology only if their main focus is the chronostratigraphical, paleoecological and/or paleogeographical importance of the taxa described therein.