The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes
The Rocas Verdes marginal basin originated during an extensional tectonic event in the Late Jurassic-Early Cretaceous, which finally led to the break-up of the Gondwana supercontinent. It is composed of mafic tholeiitic rocks with mid-ocean ridge basalt (MORB) affinity, exposed at the southernmost t...
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2010
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paper:paper_10268774_v27_n3_p431_GonzalezGuillot2023-06-08T16:00:17Z The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes Argentina Chile Gabbro Marginal basin Mesozoic Mid-ocean ridge basalt Tierra del Fuego The Rocas Verdes marginal basin originated during an extensional tectonic event in the Late Jurassic-Early Cretaceous, which finally led to the break-up of the Gondwana supercontinent. It is composed of mafic tholeiitic rocks with mid-ocean ridge basalt (MORB) affinity, exposed at the southernmost tip of South America. Magmatism occurred at spreading centers and was coeval with a calc-alkaline volcanic arc built on continental crust to the pacific side of the basin. Mafic dykes that also intrude continental crust on both sides of the marginal basin are related to the initial stages of basin development. In this contribution we present new field, petrographic, geochemical and microchemical data from gabbroic stocks and sills (the Rancho Lata Gabbro, GRL) emplaced in the northern flank of the southern tip of the marginal basin. The rocks exhibit phaneritic (gabbros) and subvolcanic (dolerites) textures. The GRL experienced greenschist facies metamorphism and mylonitic deformation. Chemical and mineralogical composition of GRL suggest that dolerites and gabbros could derive from a common parental magma, by crystal fractionation, where dolerites represent more differentiated liquids and gabbros the cumulus fraction. The GRL has tholeiitic affinity, moderate enrichment in LILE and LREE compared with normal (N)-MORB and chondrite, respectively, and high LREE/HREE ratios similar to those of enriched (E)-MORBs. On the basis of mineralogical and chemical composition, metamorphism and ductile deformation, the GRL is correlationed to other mafic dykes flanking the ophiolites reported in literature, and to the ophiolites itself from the least evolved part of the marginal basin. Therefore, the GRL most probably generated during the initial stages of basin development in an enriched upper mantle. The Nb-Ta-Ti troughs seen on normalized trace element diagrams indicate contribution of subduction components to the source. 2010 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10268774_v27_n3_p431_GonzalezGuillot http://hdl.handle.net/20.500.12110/paper_10268774_v27_n3_p431_GonzalezGuillot |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Argentina Chile Gabbro Marginal basin Mesozoic Mid-ocean ridge basalt Tierra del Fuego |
| spellingShingle |
Argentina Chile Gabbro Marginal basin Mesozoic Mid-ocean ridge basalt Tierra del Fuego The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes |
| topic_facet |
Argentina Chile Gabbro Marginal basin Mesozoic Mid-ocean ridge basalt Tierra del Fuego |
| description |
The Rocas Verdes marginal basin originated during an extensional tectonic event in the Late Jurassic-Early Cretaceous, which finally led to the break-up of the Gondwana supercontinent. It is composed of mafic tholeiitic rocks with mid-ocean ridge basalt (MORB) affinity, exposed at the southernmost tip of South America. Magmatism occurred at spreading centers and was coeval with a calc-alkaline volcanic arc built on continental crust to the pacific side of the basin. Mafic dykes that also intrude continental crust on both sides of the marginal basin are related to the initial stages of basin development. In this contribution we present new field, petrographic, geochemical and microchemical data from gabbroic stocks and sills (the Rancho Lata Gabbro, GRL) emplaced in the northern flank of the southern tip of the marginal basin. The rocks exhibit phaneritic (gabbros) and subvolcanic (dolerites) textures. The GRL experienced greenschist facies metamorphism and mylonitic deformation. Chemical and mineralogical composition of GRL suggest that dolerites and gabbros could derive from a common parental magma, by crystal fractionation, where dolerites represent more differentiated liquids and gabbros the cumulus fraction. The GRL has tholeiitic affinity, moderate enrichment in LILE and LREE compared with normal (N)-MORB and chondrite, respectively, and high LREE/HREE ratios similar to those of enriched (E)-MORBs. On the basis of mineralogical and chemical composition, metamorphism and ductile deformation, the GRL is correlationed to other mafic dykes flanking the ophiolites reported in literature, and to the ophiolites itself from the least evolved part of the marginal basin. Therefore, the GRL most probably generated during the initial stages of basin development in an enriched upper mantle. The Nb-Ta-Ti troughs seen on normalized trace element diagrams indicate contribution of subduction components to the source. |
| title |
The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes |
| title_short |
The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes |
| title_full |
The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes |
| title_fullStr |
The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes |
| title_full_unstemmed |
The Rancho Lata Gabbro: Mesozoic off-axis magmatism in the Rocas Verdes marginal basin, Argentinean Fuegian Andes |
| title_sort |
rancho lata gabbro: mesozoic off-axis magmatism in the rocas verdes marginal basin, argentinean fuegian andes |
| publishDate |
2010 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10268774_v27_n3_p431_GonzalezGuillot http://hdl.handle.net/20.500.12110/paper_10268774_v27_n3_p431_GonzalezGuillot |
| _version_ |
1768546078183915520 |