Banca de DEFESA: JOSÉ ALEXANDRE PAIXÃO DA CUNHA
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : JOSÉ ALEXANDRE PAIXÃO DA CUNHA
DATA : 22/02/2018
HORA: 16:00
LOCAL: Sala 27 - Departamento de Geologia
TÍTULO:
EMPLACEMENT MECHANISM AND THERMAL AUREOLE PROVOKED BY THE EDIACARN CATINGUEIRA PLUTON, TRANSVERSAL ZONE, BORBOREMA PROVINCE, NE BRAZIL
PALAVRAS-CHAVES:
Catingueira granite; Ediacaran; Contact metamorphism; Transversal Zone; NE Brazil
PÁGINAS: 68
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:
The Catingueira pluton (grCat), located in the Domain Transversal Zone (DTZ), Borborema Province (PB), is a classic peralkaline granite in the region with an U-Pb zircon age of 573 ± 14 Ma, intrusive into metassediments of the Santana dos Garrotes Formation (FSG), and with an exposition of approximately 12 km2. Field observations, petrography, whole rock and mineral chemistries and petrophysical properties (thermal conductivity, specific heat, thermal diffusivity and density) permitted to delimit and characterize the thermal effects caused by the grCat over the FSG. The paragenesis staurolite ± garnet ± cordierite, coexistence of chlorite and muscovite, rare sillimanite and absence of migmatization indicate low pressure and high temperature metamorphism for distances <2.5 km from the contact. These features suggest a temperature range of 520-640°C and pressure <3 kbar near the contact with the pluton. The initial temperature of the magma, calculated from whole rock zirconium geothermometer, indicates an average value of 771±19°C. The temperature assumed at the time of the intrusion, estimated from the Ti saturation of biotite of the staurolite bearing micaschist, shows an average value of 538±50°C, which is slightly higher than the temperature for staurolite stabilization with XMg ≤0.2, calculated for 520 °C (P <3 kbar). Numerical modeling considering two geometric forms (a vertical cylinder and a horizontal parallelepiped) were produced for geothermal gradients ranging from 30 °C/km to 70 °C/km. The time calculated to reach the thermal equilibrium under such conditions were of 265, 314, 552, 831 and 936 thousand years. The gradient that allowed the best fit for the model was 70 ° C/km, which is consistent with the isograd of staurolite, resulting in a time of 936 thousand years. The results obtained here in terms of dimension, shape, depth, and metamorphic assemblages are comparable to other examples of plutonic bodies described in the Seridó Belt and in other continents.
MEMBROS DA BANCA:
Externo ao Programa - 346302 - JAZIEL MARTINS SA
Externo à Instituição - VLADIMIR CRUZ DE MEDEIROS - SGB
Presidente - 350630 - ZORANO SERGIO DE SOUZA