Schedule of Mafic to Hybrid Magma Injections Into Crystallizing Felsic Magma Chambers and Resultant Geometry of Enclaves in Granites: New Field and Petrographic Observations From Ladakh Batholith, Trans-Himalaya, India

Abstract

Diorites, granites, and associated magmatic enclaves and dykes constitute the bulk of the Ladakh Batholith, which is an integral part of the Trans-Himalayan magmatic arc system. In this paper geometry of microgranular enclaves hosted in the granites has been examined from the Leh-Sabu-Chang La and surrounding regions of the eastern Ladakh Batholith to infer the mechanism and schedule of mafic to hybrid magma injections into evolving felsic magma chambers and the resultant enclave geometry. Mafic or hybrid magmas inject into felsic magma at low volume fraction (<0.35) of crystals and form the rounded to elongated microgranular enclaves in the Ladakh Batholith. Angular to subangular (brecciated), rounded to elongated pillow-like microgranular enclave swarms can also be documented as disrupted synplutonic mafic to hybrid dykes and sheets, when intruding the felsic magma with high volume fraction (>0.65) of crystals. A large rheological difference between coeval felsic and mafic magmas inhibits much interaction. Mafic magma progressively crystallizes and evolves while minimizing thermal and rheological differences. Consequently, the felsic-mafic magma interaction process gradually becomes more efficient causing the dispersion of enclave magma globules and undercooling into the partly crystalline felsic host magma. Thus the evolution of the Ladakh Batholith should be viewed as multistage interactions of mafic to hybrid magmas coeval with felsic magma pulses in plutonic conditions from its initial to waning stages of evolution.

Geochemistry and new zircon U–Pb geochronology of Mesoproterozoic Punugodu granite pluton, SE India: implications for anorogenic magmatism along the western margin of Nellore Schist Belt, India

“…The N-S-oriented nature of ME perhaps indicates the phenomenon of magmatic flowage attained during the emplacement and dynamics of coexisting ME and PG magmas (Fig. 2g) prior to solidification of the entire system as described by Kumar (2020). The FME are finegrained, linear to spherical to lenticular (Fig.…”

“…The fine-grained, igneous-textured mafic to hybrid ME from I-and A-type granites has been considered to represent mafic and/or hybrid magma components added to intermediate or felsic magma chambers (e.g. Holden et al 1987;Vernon et al 1988;Bedard, 1990;Didier & Barbarin, 1991;Bonin, 2004;Yang et al 2004; Kumar, 2020). Silica contents in the MEs indicate a broad bimodal distribution.…”

“…Further, microgranular enclaves and their distribution in felsic plutons, along with their textural and contact relationships with felsic host, may provide insights into the magma chamber processes and dynamics (e.g. Vernon, 1984;Vernon et al 1988;Kumar, 1995Kumar, , 2010Kumar, , 2020Perugini et al 2007).…”

Mafic magma-driven magmatic processes and compositional variation in granitic pluton construction: The Buya intrusion of West Kunlun, Northwestern China

“…MEs locally contain pockets with high concentrations of K-feldspar megacrysts that are interpreted to have been incorporated from the PQS host rock. Thus, even at this late stage, pockets of PQS remained in a crystal-mush state, and the mafic dikes could be syn plutonic dikes (e.g., Kumar, 2020). The amount and style of disruption of mafic magmas will depend on the specific mechanical properties of the mafic and felsic magmas, on the amount of added heat, and the strain rate (e.g., Andrews and Manga, 2014).…”

“…The replenishment of dense mafic magmas can lead to an interplay or magma mingling and local mixing (Hildreth, 1981;Huppert and Sparks, 1988;Streck and Grunder, 1999;Sparks and Sigurdsson, 1977;Barnes et al, 1986;Metcalf et al, 1995;Jellinek and Kerr, 1999;Bergantz et al, 2015;Wiebe and Hawkins, 2015), incremental assembly (Glazner et al, 2004;Coleman et al, 2004;Miller et al, 2011), crystal (mush) resorption, magma convection and homogenization, and crystal-liquid segregation in the magma reservoirs (e.g., DePaolo, 1981;Wiebe and Collins, 1998;Bachl et al, 2001;Miller and Miller, 2002;Weinberg, 2006;Collins et al, 2006;Walker et al, 2007;Pupier et al, 2008;Deering and Bachmann, 2010;Turnbull et al, 2010;Gelman et al, 2014;Barnes et al, 2016;Schaen et al, 2017;Bachmann and Huber, 2019). Discussing the relative timing of intrusion and geometry of mafic magmatic inclusions/dikes/sheets hosted in granites (Kumar, 2020) is important. Many of these processes may individually play a dominant role in specific plutons, parts of plutons, or periods of plutonic growth (Pupier et al, 2008).…”