DOI: 10.1007/s00531-014-1020-y
Scopus记录号: 2-s2.0-84900020368
论文题名: Origin and age of ultramafic rocks and gabbros in the southern Puna of Argentina: An alleged Ordovician suture revisited
作者: Zimmermann U. ; Bahlburg H. ; Mezger K. ; Berndt J. ; Kay S.M.
刊名: International Journal of Earth Sciences
ISSN: 14373254
出版年: 2014
卷: 103, 期: 4 起始页码: 1023
结束页码: 1036
语种: 英语
英文关键词: Argentina
; Pampia Terrane
; Puna-Famatina magmatic arc
; Ultramafic and mafic rocks
; Western Gondwana margin
Scopus关键词: crustal contamination
; gabbro
; Gondwana
; mafic rock
; Ordovician
; plate boundary
; suture zone
; ultramafic rock
; Argentina
; La Rioja [Argentina]
; Puna
; Sierra de Famatina
; Sierras Pampeanas
英文摘要: Ultramafic rocks and gabbros are exposed in the southern Puna (NW Argentina) in tectonic association with continental arc-related Ordovician (volcano) sedimentary successions and granitoids. The origin of this mafic rock suite has been debated for three decades as either representing an Ordovician terrane suture, primitive Ordovician arc-related rocks or relics of the pre-Ordovician basement in tectonic contact with the Ordovician retro-arc basin successions. We present the first U-Pb ages of primary and inherited zircon from gabbros of this mafic-ultramafic assemblage. LA-ICP-MS analyses on cores and rims of these zircon grains yielded a concordia age of 543.4 ± 7.2 Ma for the gabbroic rocks. Other analysed zircons have Mesoproterozoic, and Early Ediacaran core and rim ages indicating that the magmas also assimilated Meso- and Neoproterozoic crustal material prior to final crystallization. The mafic rocks witnessed higher metamorphic grade than associated Ordovician rocks, which are unmetamorphosed or only affected by anchimetamorphism. The gabbros are mostly tholeiitic and enriched in Zr, Th, as well as other incompatible elements and have εNdt=540Ma ranging from 1.3 to 7.4 with most of the values between 5 and 7. 147Sm/144Nd ratios show evidence of weak crustal contamination. The mafic rocks do not reveal any affinity to mid-ocean ridge basalts in their geochemistry but point instead to an emplacement in an active plate margin arc environment. Chromites from ultramafic rocks show typical Ti, Al, Cr#, Fe3+ abundances found in magmatic arc rocks. The formation of the gabbros and the associated ultramafic rocks in the southern Argentine Puna is related to the evolution of the margin of the Pampia terrane, including the Puncoviscana basin, during the Late Neoproterozoic and earliest Cambrian. In contrast to previous interpretations, the rocks predate the Ordovician evolution of the Central proto-Andean active margin. Consequently, interpretations assuming these rocks to represent an oceanic terrane suture of Ordovician age have to be dismissed as much as all palaeotectonic models that define Ordovician terranes in the Central Andes based on assumption that the ultramafic rocks and gabbros exposed in the southern Puna mark plate boundaries. © 2014 Springer-Verlag Berlin Heidelberg. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84900020368&doi=10.1007%2fs00531-014-1020-y&partnerID=40&md5=5e19d105beb2ae437457be84150037fa
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/70379
Appears in Collections: 影响、适应和脆弱性 气候减缓与适应
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作者单位: Department of Petroleum Engineering National IOR Center, University of Stavanger, 4036 Stavanger, Norway; Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität, Corrensstrasse 24, 48149 Münster, Germany; Institute of Geological Sciences, University of Bern, Baltzerstrasse 13, 3012 Bern, Switzerland; Institut für Mineralogie, Westfälische Wilhelms-Universität, Corrensstrasse 24, 48149 Münster, Germany; Department of Geological Sciences, Cornell University, Ithaca, NY, 14853, United States
Recommended Citation:
Zimmermann U.,Bahlburg H.,Mezger K.,et al. Origin and age of ultramafic rocks and gabbros in the southern Puna of Argentina: An alleged Ordovician suture revisited[J]. International Journal of Earth Sciences,2014-01-01,103(4)