Time resolved construction of a bimodal laccolith (Torres del Paine, Patagonia)

Abstract: Granitic and mafic magma pulses were sequentially accreted in the spectacularly exposed shallow crustal Torres del Paine laccolith, in southern Patagonia. This 12.5Ma pluton forms a composite intrusion with a subvertical feeding system in the west and a laccolith in the east. A key unknown in the formation of sill complexes is how individual magma pulses are assembled over time and the geometry and localization of their feeding system. High resolution zircon CA-ID-TIMS U–Pb dating shows that the laccolith grew first by under-accretion of granitic sills over 90±30ka, linked to a ‘sheet-like’ feeding system, followed by underplating of mafic sills after ~20ka of quiescence. In the mafic sills complex, individual sills were injected by over-accretion during 41±11ka. Our data show that successive granitic and mafic magmas emplacement generated a volume of ~88km3 in 162±11ka. [Copyright &y& Elsevier]