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Mass transference from lower to upper crustal levels requires an efficient network of pathways that act as channels for draining melts from the source and transferring magmas through the crust. We report on a mid-crustal section in the Santa Rosa river from the Eastern Pampean Ranges that underwent partial melting under active deformation. The study focuses on the feedback relations between structural features and the position and shape of leucosomes that record the remnant magma network in both metasedimentary and meta-igneous rocks. A complete range of migmatites encompassing from patch to stromatic metatexite to schollen-schlieren and nebulitic diatexite formed during a single high-grade metamorphic event that postdated a previous sub-solid evolution. The diversity in migmatites structures suggests that the layered sequence behaved heterogeneously under a non-coaxial deformational regime of progressive deformation. The relationships between migmatitic structures and the progressive production of melts resulted in feedback relations that persisted as a time-marker during the Pampean event. U-Pb dating of leucogranitic zircons allows constraining the time of melt generation and segregation to the lower Cambrian (534-520 Ma). Migmatites in the lower crust of the Pampean orogen acted as channels of melt migration towards upper crustal levels. • Non-coaxial Pampean deformation and its relationships with migmatitic structures. • A melt transference zone documented from a middle crustal ancient accretionary orogen. • Geochronology shows that syn-deformational migmatites generated during lower Cambrian. • Axial-plane leucosomes work out as melt-removal paths towards upper crustal levels. [ABSTRACT FROM AUTHOR]

The Valle Fértil-La Huerta batholith is a differentially tilted, compositionally stacked, calc-alkaline plutonic sequence in the central Famatinian arc of Argentina. It consists of two major lithologic units: these are (1) an intermediate unit largely dominated by amphibole- and biotite-bearing tonalites but encompassing from gabbro to leucogranite; and (2) an overlying silicic unit that shows the same petrological diversity as the intermediate unit, but granodiorite and monzogranite are its prevailing lithologies. The silicic unit is separated into four subunits using lithological changes at regional mapping scale. All the boundaries are gradational among lithologic units and subunits. The internal fabric along the entire batholith is either magmatic or submagmatic and it was developed during the arc formation. The original magmatic foliation is north–south striking and steeply-dipping. The magmatic foliation crosses over and transposes the gradational contacts among lithologic units. Petrological architecture, structural geology, geobarometric estimates and geochronology show that the entire batholith is a comagmatic system exposing more than 13 km of a middle arc crust. Crystallization-fractionation models computed using whole rock and mineral chemistry account for the mineralogy of plutonic rocks and coincide with the results of experimental petrology. Mass-balanced modeling predicts that the unexposed cumulate roots of the Famatinian arc should have been about 1.3 times larger than the intermediate and silicic plutonic batholith. However, the mass of calculated cumulate would diminish significantly if a portion of the host metasedimentary material were consumed in constructing the batholith. The batholith grew progressing upward from the lowest levels and acquired a stratified compositional organization. The driving mechanism was continuous influxes of mantle-derived mafic magmas that made up the lower crust, caused crustal-level melting and magma mixing, and formed intermediate – silicic rocks at increasingly shallower depths. • The plutonic middle crust of the Famatinian arc was at least 13 km thick. • The plutonic crust grew progressing upward and acquiring a stratified organization. • Pre-arc metasedimentary sequences play a role in fertilizing the magmatic system. • Modeling yields a 1.3:1 ratio of cumulates over derivatives to make the magmatic column. • A few tens of kilometers of cogenetic cumulates are lost in the Famatinian arc. [ABSTRACT FROM AUTHOR]