Banca de DEFESA: SERGIO VIEIRA FREIRE BORGES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : SERGIO VIEIRA FREIRE BORGES
DATA : 19/08/2016
HORA: 14:30
LOCAL: A definir
TÍTULO:

Pedogenic calcretes within fracture systems and beddings in Neoproterozoic limestones of the Irecê Basin, Northeastern Brazil.

PALAVRAS-CHAVES:

calcretes, caliches, Irecê Basin, calcretes along fault systems and beddings.

PÁGINAS: 52
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

Calcretes or caliches are continental limestones developed by surficial weathering process that takes place mostly in arid and semi-arid regions. In the Irecê Basin, northeastern Brazil, in addition to the regular occurrence of pedogenic calcretes, a peculiar type of structurally controlled calcretes occurs on Neoproterozoic limestones. These peculiar calcretes developed near the surface and occur (1) between layers, (2) inside fractures and (3) within major thrust faults. Fieldwork on selected outcrops was integrated with petrographic, mineralogic, geochemical, density and mercury intrusion porosity analyses to constrain the environment of formation and their petrophysical properties. The results revealed that this type of calcrete is the product of multiepisodic events of dissolution and precipitation occurring during the wet and dry seasons in the region along fractures and beddings. Based on the petrophysical results, we suggest that these calcretes may have an important role in the migration of fluids through the impermeable host carbonate rock and that they act as a conduit for fluid flow, as revealed by their high porosity (mean value = 26%) and remarkable pore connectivity. 

MEMBROS DA BANCA:
Externo à Instituição - Augusto Sarreiro Auler - NENHUMA
Externo ao Programa - 1161652 - FRANCISCO PINHEIRO LIMA FILHO
Externo à Instituição - LEAO XAVIER DA COSTA NETO - IFRN
Presidente - 277437 - MARCELA MARQUES VIEIRA
Externo ao Programa - 347536 - NARENDRA KUMAR SRIVASTAVA