Mecanismo de colocação e auréola termal provocada pelo plutão ediacarano Catingueira, Zona Transversal, Província Borborema, Nordeste do Brasil
The Catingueira pluton, located in the state of Paraíba, 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...
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| Formato: | Dissertação |
| Idioma: | por |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/25505 |
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| Resumo: | The Catingueira pluton, located in the state of Paraíba, 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 Catingueira granite 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. |
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