Description
The Lang sequence has undergone five phases of structural deformation. D-1 produced N-S trending tight to isoclinal folds believed to be associated with accretionary processes. D-1 structures are truncated by the Bowman Lake batholith (375 + 10 Ma) and by quartz porphyry dikes (340 +4 Ma). D-1 is therefore pre-Middle to Late Devonian. D-2 produced domainally developed NNE-trending folds and cleavage, and is related to the emplacement of the granodiorite phase of the Emigrant Gap pluton, dated at 165 +2 Ma. Supporting evidence for this interpretation include relationships between porphyroblasts and D-2 fabric in the contact aureole of the pluton, the geometrical and spatial association of D-2 structures with the pluton, and pre- to syn-tectonic plagioclase porphyry dikes/sills dated at 166 +2 Ma. D-3 produced pervasive NW-trending cleavage interpreted to be related to the Late Jurassic Nevadan orogeny. D-4 produced domainally developed NW trending crenulation cleavage and folding. D-5 produced domainally developed NE trending crenulation cleavage. There is a younging of deformation to the west, and it is speculated that D-3, D-4, and D-5 record differential movement histories associated with the Melones fault zone.
