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Título

INTEGRATED ANALYSIS BY U-TH/HE IN ZIRCON AND FISSION TRACK IN APATITE APPLIED IN THE ELLSWORTH MOUNTAINS, ANTARCTIC PENINSULA

Texto do resumo

: The Ellsworth Mountains extend for ~350 km between the Transantarctic Mountains and the Antarctic Peninsula and are ~50 km wide. They are located within West Antarctica, which is composed of crustal blocks that amalgamated along the Pacific margin of Gondwana during the latest Precambrian to middle Phanerozoic. Furthermore, the Ellsworth Mountains form part of the most isolated and enigmatic crustal block in West Antarctica and exhibit an exceptionally well-preserved Palaeozoic sedimentary sequence However, while thermochronological studies have constrained the landscape evolution of several of the crustal blocks of West and East Antarctica, the tectono-thermal evolution of the Ellsworth Mountains remains relatively poorly constrained. In this work are presented U-Th/He in zircon (ZHe) ages. These ages provide insights into the landscape evolution of the Ellsworth Mountains because they suggest that these rocks buried burial reheating after deposition. A cooling event is recorded during the Jurassic–Early Cretaceous, which we interpret as representing exhumation in response to the rock uplift of the Ellsworth Mountains. Furthermore, our results show that while ZHe ages at the base of the sequence are fully reset, towards the top ZHe ages are partially reset. Uplift and exhumation of the Ellsworth Mountains during the Jurassic–Early Cretaceous was contemporary with the rotation and translation of this crustal block concerning East Antarctica and possibly the Antarctic Peninsula. Based on these results, we suggest that the uplift of the Ellsworth Mountains during the disassembly of Gondwana provides additional evidence for major rearrangement of the crustal blocks between the South American, African, Australian, and Antarctic plates. Finally, the uplift of the Ellsworth Mountains began during the Jurassic, which predates the Early Cretaceous uplift of the Transantarctic Mountains. We suggest that the rift-related exhumation of the Ellsworth Mountains occurred throughout two events: (i) a Jurassic uplift associated with the disassembly of southwestern Gondwana and (ii) an Early Cretaceous uplift related with the separation between Antarctica and Australia, which is also recorded in the Transantarctic Mountains. Furthermore, new data obtained via the Apatite Fission Track (AFT) are being acquired to complement the conclusions established so far.

Palavras Chave

U-Th/He; Fission Track; zircon; apatite; Ellsworth Mountains