A QUANTITATIVE ASSESSMENT OF THE EFFECTS OF MAGMATISM ON THE THERMAL HISTORY OF THE KAROO SEDIMENTARY SEQUENCE

被引：41

作者：

BROWN, R

GALLAGHER, K

DUANE, M

机构：

[1] Research School of Geological and Geophysical Sciences, University and Birkbeck Colleges, London, WC1E 6BT, Gower Street

[2] School of Geological Sciences, Kingston University, Kingston-upon-Thames, KT1 2EE, Penrhyn Road

[3] Department of Geology and Applied Geology, University of Natal, Durban, 4001, King George V Avenue

[4] Environmental Institute, Commission of the European Communities, Joint Research Centre, 21020 ISPRA, Varese

来源：

JOURNAL OF AFRICAN EARTH SCIENCES | 1994年 / 18卷 / 03期

关键词：

D O I：

10.1016/0899-5362(94)90007-8

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

Simple 1-D numerical and analytical thermal models are used to quantify thermal effects of magmatic processes affecting the upper approximately 5km of the crust. The model results suggest that maximum palaeotemperature estimates, derived from vitrinite reflectance profiles and zircon fission track data from the Karoo basin, are not easily explained by increased burial in the past or by heating caused by high level intrusions if the excess heat was dissipated only by conduction. Heavy mineral deposits associated with uranium mineralization in the karoo basin show signs of significant hydrothermal alteration, similar to that documented from other uranium provinces. New fission track data from detrital zircons from two sedimentary-hosted uranium ore deposits (Rietkuil and DR-3 Laingsburg) implies that these deposits experienced maximum palaeotemperatures of at least 250+/-50-degrees-C subsequent to deposition (for heating times of the order of 10(6) yr). Moreover, the distribution of fission track ages for single zircon grains suggests that peak temperatures were reached during the period of karoo magmatism at approximately 190+/-10 Ma. Taken together, these observations provide strong evidence for the existence of magmatically driven hydrothermal systems within the Karoo basin and their probable generic association with uranium mineralization.

引用

页码：227 / 243

页数：17

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