In an ocean-continent subduction zone, the assessment of the lithospheric thermal state is essential to determine the controls of the deformation within the upper plate and the dip angle of the subducting lithosphere. In this study, we evaluate the degree of influence of both the configuration of the upper plate (i.e., thickness and composition of the rock units) and variations of the subduction angle on the lithospheric thermal field of the southern Central Andes (29°–39°S). Here, the subduction angle increases from subhorizontal (5°) north of 33°S to steep (~30°) in the south. We derived the 3D temperature and heat flow distribution of the lithosphere in the southern Central Andes considering conversion of S wave tomography to temperatures together with steady-state conductive thermal modeling. We found that the orogen is overall warmer than the forearc and the foreland and that the lithosphere of the northern part of the foreland appears colder than its southern counterpart. Sedimentary blanketing and the thickness of the radiogenic crust exert the main control on the shallow thermal field (<50 km depth). Specific conditions are present where the oceanic slab is relatively shallow (<85 km depth) and the radiogenic crust is thin. This configuration results in relatively colder temperatures compared to regions where the radiogenic crust is thick and the slab is steep. At depths >50 km, the temperatures of the overriding plate are mainly controlled by the mantle heat input and the subduction angle. The thermal field of the upper plate likely preserves the flat subduction angle and influences the spatial distribution of shortening.

Mineral chemistry of the magmatic biotites from the syn-mineral dacitic porphyry of Morro del Cobre.
Mineral chemistry of the magmatic biotites from the dacitic porphyry of Morro del Cobre (Frontal Cordillera of San Juan province) reveals that they are Mg-biotites, typical of precursor porphyry Cu intrusives. Biotite geothermobarometry confirms the hydrous and oxidant character of the magma which evolved to shallower chambers

Clay mineral characterization is a valuable tool for unraveling the evolution of continental sedimentary basins. The Fiambala ´ basin is a foreland Andean basin located in the Southwest of the province of Catamarca (Argentina), on the flat subduction segment. In order to characterize its paleoenvironment and post-depositional evolution, petrographic, X-ray diffraction (XRD), and scanning microscopy (SEM-EDS) studies were carried out in detrital and volcaniclastic samples from the Tambería, Guanchín, and Rodados de la Puna Fms. Petrographic and XRD analyses show a predominance of phyllosilicates, quartz, plagioclase, and low proportions of feldspar and anhydrite, sporadic calcite, analcime, heulandite, and hematite. In the XRD fraction <2 μm, minerals from the smectite and illite groups dominate, with lower proportions of chlorite and kaolinite. An analyzed tuff level presents smectite solely in this fraction. The textural-compositional analyses of SEM-EDS show that illite and chlorite have a detrital origin. Their preservation would be consistent with the dominance of an arid climate in the region during the erosion and deposition of material from the source areas. The smectites are of the magnesium-rich beidellite-montmorillonite type and, together with the zeolites would be authigenic as a product of the alteration of both the volcanic material and magnesian detrital phases (chlorite and biotite), possibly under the influence of an alkaline environment related to the arid climate. From a thermal point of view, the presence of smectite throughout all stratigraphic succession allows interpreting maximum temperatures that, even in the deepest levels of the basin, inhibit the development of prograde phases (such as smectite/illite and smectite/chlorite mixed-layered) and allow the preservation of smectite. Based on the authigenic clays present in the basin, paleogeothermal gradients of between 13 and 18 ◦C/km (considered a fill of 4000 m thick) and between 8 and 11 ◦C/km (considered a fill of 6000 m thick) could be estimated.

New X-ray diffraction (XRD) data, scanning electron microscopy (SEM) analysis, and X-ray energy dispersive spectrometry (EDX) microanalysis on clay minerals are presented for Cretaceous-Cenozoic sedimentary sections studied in the La Flecha and La Troya Sur creeks, located in the Argentine Precordillera. The characterization of clay mineral assemblages, including the discrimination of detrital and authigenic phases, allows inferences to be made about paleoclimatic and paleoenvironmental conditions as well as the postsedimentary history of these foreland clastic sedimentary depocenters. Mineralogical analyses carried out in the Cretaceous Ciénaga del Río Huaco Fm. and the Cenozoic Puesto La Flecha, Vallecito, Vinchina, and Zapallar Fms. show the presence of illites, smectites, illite/smectite mixed-layer clays (I/S, with R0 and R1 ordering types), sporadic corrensite, and subordinate amounts of chlorite and kaolinite, among other non-clay phases, such as analcime and heulandite. Illite and chlorite are interpreted as detrital phases, reflecting the composition of the source area, and smectite, I/S R0 and R1, and corrensite are interpreted as authigenic phases developed in the matrix or as massive pore filling within the clastic levels. Compositional analyses allow for smectites to be characterized as di- and trioctahedral Mgrich, and are interpreted as a product of the combination of two main controls: (1) that from the parent material (volcaniclastic material and magnesian silicates) and (2) that of the primary composition of pore fluids associated with alkaline lake systems. These smectites are precursors of prograde diagenetic phases developed under a low thermal regime (< 120 °C). R0 and R1 I/S formed from Mg-dioctahedral smectites mainly within the matrix, with an increase of illite % in R0 and R1 with depth, and corrensite formed from trioctahedral Mgsmectites mainly as massive pore fillings. Finally, the conclusions obtained from these new data reinforce that, in some cases, authigenic phases associated with mesogenesis (e.g., corrensite) would allow us to make inferences about the precursor authigenic material and
therefore about some paleoenvironmental conditions. This, in turn, underlies the importance of making detailed analyses of clay mineral assemblages in reconstructions of the sedimentary and post-sedimentary history of basins close to areas with active tectonism, such as foreland basins.

The morphology and evolution of diapirs and mud volcanoes in the Colombian Caribbean Margin (MCC) located in transgressive Cretaceous to Neogene sedimentary sequences are analyzed in this paper. They are extrusive structures by argilokinesis that show the release of overpressure and fluidized sediments by water and/or hydrocarbons that pierce the surface. From the analogical modeling of the determining factors of origin and geometry, the diapirism mechanisms depend on: i) the lower density of the underlying generating levels compared to the overlying sequences, and ii) the weak sedimentation rates of the overlayered sequences. The progressive exhumation of the Sinú-San Jacinto Belt from the Oligo-Miocene period due to the dextral transpressive tectonic convergence between the South American and Caribbean plates, generated a barrier to sedimentary transport to the North of the Paleo Cauca River. This interruption prevented its direct discharge, forcing it to coalesce into the Magdalena River, increasing the volume of its delta. A provincialism of diapirism is proposed based on the differences in rates and chronologies of the progradation of denser sediments on pelitic sequences associated with conspicuous types of folds: a) to the north (San Jacinto Belt), tangential compressional type with a double plunge, and oriented subparallel to the Caribbean coast, and b) to the south (Sinú Belt), gravitational type with wide synclines and tight anticlines. Better knowledge of the 4D evolution of MCC diapirism contributes the potential of the underlying oil systems and the prevention
of environmental risks in exploratory maneuvers.

The Agua de la Zorra Formation (Uspallata Group) constitutes the rift infill of the Paramillos depocenter from the Cuyo basin located in the Argentine Precordillera. This unit hosts the Paramillos de Uspallata polymetallic vein-deposit. In this contribution we report a new LA-ICP-MS zircon U-Pb age of 230.2 ± 2.2 Ma (Upper Triassic) for a tuff level that belongs to the Agua de la Zorra Formation. The obtained age is consistent with the age of the volcanism in other areas of the Cuyo basin.

The Sierra Nevada de Santa Marta (Santa Marta) in Colombia and Nevado del Famatina (Famatina) in Argentina are two isolated peaks within the Andes of South America, having elevations of about 5,500 and 6,000 m, respectively. Both massifs are bounded by major wrench faults of opposite kinematics but comparable magnitude in their lateral displacement. Despite the volumes of research available, little has been said in the literature about the tectonics surrounding these particular systems. In this context, digital terrain elevation (DEM), regional geology, satellite imagery and geophysical data were analysed to illustrate how a network of transcurrent faults uplifted the peaks. We propose a model to account for topography by the opposed movement of faults operating in two compartments: internal (acute) and external (obtuse). Fault motion caused uplift of the internal compartments: a) the Santa Marta tectonic syntaxis is generated by the sinistral Santa Marta-Bucaramanga Fault on the west and the dextral Oca-Pilar Fault to the north whilst, b) the Famatina tectonic syntaxis is caused by the Valle F´ertil sinistral fault on the western side and the dextral Tucum´an lineament to the north. Elevation maps documenting the lateral displacement of modern alluvial fans provide evidence of the existence and kinematics of these faults. Active since the Neogene, the transcurrent faults resulted in displacements in the order of 25–60 km, with velocities of approximately 1–2 cm/year. Seismic records suggest that the syntaxis occurred after reactivation of oblique discontinuities in the basement due to the convergence of the Nazca, Caribbean, and South American plates. This tectonic framework led to the formation of a remarkable positive relief and the development of internal positive compartments subject to onstrictive forces. Simultaneously, external distensive and negative compartments controlled the syntectonic deposition of thick sedimentary sequences. The significant topographic difference between the internal positive compartments and their external negative counterparts triggered high rates of erosion, transport, and ultimately sedimentation. Regional subsurface surveys indicate strong anomalies of the underlying bedrock influenced by tectonic syntaxis.