Roof and walls of the Red Mountain Creek pluton, eastern Sierra Nevada, California (USA): implications for process zones during pluton emplacement

Abstract

The Red Mountain Creek pluton has a sub-circular outline in map section, generally flat roof, and steep sides. The pluton roof sharply truncates host rock markers, has a highly irregular geometry with rectangular steps, and passes continuously into a steep wall. The roof–wall transition is not offset by faults and shows no evidence of extensive diking or synemplacement ductile strain, which requires that the pluton roof and its wall remained attached to each other and were not faulted or ductilely deformed during emplacement of the pluton. We propose that the exposed section through the Red Mountain Creek pluton may represent the crestal portion of a vertically extensive piston-shaped plutonic system, the upper part of which was largely emplaced by magmatic stoping although other material transfer processes may have previously operated during emplacement. Characteristics of the pluton roof presented in this paper as well as in other papers on pluton roofs directly rule out some emplacement models commonly applied to plutons in the Sierra Nevada, place limitations on other models, and fit well the expected characteristics of visco-elastic diapirs around which variable material transfer processes largely displace host rock downwards. In the upper-crustal plutons, the most widespread preserved process of downward transport of host rock was magmatic stoping.