The Antioquia batholith represents the magmatic record of the interaction between the Farallón and Caribbean plates with the NW part of the South American Plate during the Meso-Cenozoic. Several authors have reported zircon U-Pb ages and whole rock geochemistry in order to constrain the crystallization history of this batholith and its formation conditions. The present work aims to gather the existing data with new data obtained from the Ovejas batholith and La Unión stock, both genetically related to the main intrusion. Gathering our new data with information obtained in previous works, we conclude that the Antioquia batholith was constructed by successive pulses from ca. 97 to 58 Ma in an arc-related setting. The initial pulses are related to syn-collisional tectonics, during the early interaction between the Farallón plate and NW South America. The final pulses, that record Eocene ages, are related to a post-collisional setting, similar to that recorded in other plutons of the Paleogene magmatic arc of the Central Cordillera.
The rheology of crustal mushes is a crucial parameter controlling melt segregation and magma flow. However, the relations between mush dynamics and crystal size and shape distribution remain poorly understood because of the complexity of melt‐crystal and crystal‐crystal interactions. We performed analog experiments to characterize the mechanisms that control pore space reduction associated with repacking. Three suspensions of monodisperse particles with different geometries and aspect ratios (1:1, 2:1, 4:1) in a viscous fluid were tested. Our results show that particle aspect ratios strongly control the melt extraction processes. We identify two competing mechanisms that enable melt extraction at grain scale. The first mechanism leads to continuous deformation and melt extraction and is associated with “diffuse” frictional dissipation between neighboring particles. The second is stochastic, localized, and nearly instantaneous and is associated with the development and destruction of force chains percolating through the granular assembly.
Angrite meteorites are a small subgroup of basaltic achondrites characterized as mildly silica undersaturated, with unusually high Ca and Al contents [1]. The Angrite Parent Body (APB) may have been comparable in size to Vesta as it had a core dynamo [2], providing evidence of asteroid interior differentiation ~4.5 billion years ago, in the early stages of the Solar System [1,3]. The differentiation on the APB occurred at much lower gravity; was driven by early, intense heat sources; and operated over more reducing conditions [1,4] than in today's Earth interior. Nevertheless, the genesis of angrites is not well understood partly because of the small number of specimens available and their significant chemical variation. Our experimental study aims to constraint the petrogenesis of an MgO-rich group of angrites (Asuka881371, LEW87051, NWA1670 [5]) that possibly represents primary igneous activity produced by melting in the APB mantle.We used a series of melting experiments conducted on two angrite primary compositions to constrain the oxygen fugacity (O2), temperature, extent of melting, and phase equilibrium conditions of this subset of plutonic angrites. Our preliminary results indicate that one group of angrites experienced crustal level Ol-Plag-Cpx fractional crystallization. We determined the near-liquidus phase relations and petrogenesis of the MgO-rich quench angrites by carrying out experiments over 2.4 GPa and >1350°C with an O2 similar to that calculated for LEW86010 (~IW+1, [4]). The melting conditions of this group of samples may represent an end member in our understanding of largescale igneous processes in the early Solar System. Using our experimental data, we will provide new estimations on the minimum size of the APB based on our temperature-pressure melting relations.
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