| Popis: |
The Triassic magmatism found in the South-Central Andes is interpreted to be formed by a stage long-lived arc activity, product of attenuated subduction, in a transition from the final assembly of Gondwana and the initiation of its breakup, namely post-orogenic magmatism. As a result, the younger part Elqui-Limarí batholith (BEL) was formed, covering an area above 5,000 km2. The geodynamics of this transition characterize a resulting thinned lithosphere, the generation of regional-scale NNW-SSE marginal basins and volcanism as an analog to an island arc setting, and bimodal magmatism. The latter is portrayed by (1) the upwelling of mantle-derived magmas through diking (Elqui Dike Swarm) by crust relaxation; and (2) The intrusion of scattered plutons of anorogenic and arc-related geochemical affinities, rapidly extracted from long-lived reservoirs located in the base of the crust, and emplaced at a shallow level, piercing the Upper Paleozoic granitic basement. The latter was vigorously uplifted and exhumed in the Late Triassic, as a consequence of extensional conditions, concomitant with profuse volcanism (mainly the Pastos Blancos Formation, among other products).Our results indicate that the volcanic coverage of the BEL is genetically related to its intrusive counterpart. The Rb/Sr ratios of the epizonal plutons (>0.4) are consistent with extracted liquids from deeper parts of the magmatic system, whereas the Pastos Blancos Formation present mixed signals, interpreted to be product of the high antecrystic load, evacuated from ‘mushy’ parts of the magmatic reservoir. Plutons emplaced at greater depth (>3 kbar) show Rb/Sr ratios (optimal melt extraction efficiency window (crystallinities between 50 to 70 vol.%) show a remarkable resemblance with crystal clots observed in the Pastos Blancos Formation, supporting the idea of a connection between the Triassic plutons found in the BEL and its contemporaneous volcanic coverage. |
