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The La Felipeña prospect and other mineral occurrences located in the periurban area of San Felipe (Baja California) consist of quartz-carbonate veins with low sulfides, white mica, and tourmaline, which are characterized by anomalous Au contents. The veins are hosted in Paleozoic greenschist facies metasedimentary rocks and in quartz-dioritic dikes that intrude the former. In this study, we present two radiometric dates that constrain the age of mineralization in La Felipeña between ~94 and 83 Ma. A sample from a hosting dike yielded a U-Pb zircon age of 94.0 ± 0.8 Ma. The lower limit corresponds to a 40Ar/39Ar age for hydrothermal white mica of 82.73 ± 0.14 Ma. Fluid inclusion studies in hydrothermal quartz yielded trapping temperatures between ~400° y 530 ℃, trapping pressure at ~210 MPa, and salinities of ore-bearing fluids between 5 and 14 wt.% NaCl equiv. The formation of this deposit was partially associated with effervescence. The La Felipeña deposit exhibits similar characteristics to those of the orogenic gold type and is the first documented case of this style of mineralization formed during the transition between the Peninsular Ranges orogeny (~110-90 Ma), which is related to the culmination of the construction of the Peninsular Ranges batholith, and the Laramide orogeny sensu lato (~90-40 Ma), associated with an increased convergence rate between the Farallon and North America plates. The gold mineralization in the San Felipe area provides evidence for the spatial-temporal continuity between the Peninsular Ranges (~106-92 Ma) and Caborca (~77-36 Ma) orogenic gold belts at the easternmost Peninsular Ranges batholith. [ABSTRACT FROM AUTHOR]

Studying the exhumation history and surface uplift in mountainous regions are key to understand how inversion orogens are built. In this contribution, we study the exhumation history on the central sector of the Colombian Eastern Cordillera; this region includes the Boyacá and Soapaga thrust faults and other minor faults. To reconstruct the exhumation history of this area, a compilation of existing thermochronological data was carried out. This data was used to perform inverse 3D thermal-kinematic modeling, to compare predicted versus observed ages and to estimate exhumation rates of tectonic blocks. The results suggest an asynchronous exhumation pattern. The area between the Boyacá and Soapaga faults experiences two exhumation pulses at 69.1 and 15.7 Ma with rates of 0.91 and 0.16 km/Ma, respectively. In contrast, in the footwall block of the Soapaga fault, an exhumation episode of 22.7 Ma was discriminated at a rate of 0.49 km/Ma. This last sector coincided with a significant accumulated seismic uplift during the last 5 Ma, obtaining seismic uplift values between 70 and 100 m/Ma. Analysis of the relation magnitude-frequency of earthquakes allow us obtaining b-values for the hanging block of Soapaga fault of 0.55 ± 0.01, consistent with mechanisms associated to transpressional tectonics. However, the numerical model suggests a surface rejuvenation between 6 to 9 Ma for a sector of the study area. With the purpose of discriminating against other processes that could cause such rejuvenation, other variables were incorporated as precipitation data, normalized steepness index (ksn in rivers), hypsometric integral and relief. Strong correlations were discriminated between seismic relief and deformation, and seismic relief and uplift in the zone of greater exhumation, which suggests the tectonic forces exert a greater control on the relief in the short term as well as in the long term. Additionally, a highly active seismic region was identified for the study zone that had not been discriminated against. [ABSTRACT FROM AUTHOR]