Seamless low-temperature thermochronological modeling in Andino 3D, towards integrated structural and thermal simulations

BALCIUNAS DANIEL; NIGRO JOAQUIN; ERNESTO CRISTALLINI; MORA ANDRES; JUAN HERNANDEZ; NASSIF FRANCISCO SANCHEZ; KETCHAM RICHARD; ROBERTO HERNANDEZ

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020 vol. 105 p. 1 - 8

0895-9811

We present the development of thermochronological tools for Andino 3D® software, following the previous development of Fetkin (Finite Element Temperature Kinematics). This tool allows the user to work on both the structural and the thermochronological model at the same time, providing a user-friendly environment that overcomes the need to work with different programs. Thermochronological and structural models can be checked and eventually corrected in a visual and intuitive form, by following a 4-step workflow. The first step of such workflow is to define the thermochronological computing grid, checking in real time, if the resolution and coverage are satisfactory. After that, the interpolation process can be done, whereby velocity vectors for all nodes in beds and faults are calculated for all interpolated times. The third step of the workflow consists in filling thermal properties and velocities for all grid cells. The final step is the calculation of the thermal state at each time in the reconstruction. Boundary conditions (basal temperature, basal heat flow, surface temperature and altitude gradient) are easily defined as constant, spatially varying, time varying or spatially and time varying. To check the feasibility of a structural model, thermochronological samples can be defined at desired positions to predict time-temperature variations. Simulated fission track ages, mean track lengths and age standard deviations can be calculated for different minerals (apatite and zircons). Also, cooling ages and %Ro can be simulated for (U-Th-Sm)/He and vitrinite systems, respectively. The Carohuaicho structure in the southern Bolivia sub-Andean Ranges is presented as a case of study to test the mentioned tools. Andino 3D® allowed to successfully simulate the t-T paths of four samples where (U-Th-Sm)/He measurements were available. The different models performed permitted to conclude that, likely, a low geothermal gradient was present during the last 7 Ma of Andean deformation in the study region.