The genesis of sub‐basaltic Silcretes from the Monaro, New South Wales
作者:
G. Taylor,
I. E. Smith,
期刊:
Journal of the Geological Society of Australia
(Taylor Available online 1975)
卷期:
Volume 22,
issue 3
页码: 377-385
ISSN:0016-7614
年代: 1975
DOI:10.1080/00167617508728903
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Sub‐basaltic silcretes are widespread in the Monaro, New South Wales, and their origin has been hitherto linked with eruption of the overlying basalt. Investigation of silcretes from three localities in the Monaro at granite‐basalt, shale‐basalt, and basalt‐basalt contacts, has revealed a complex history of depositional events in these rocks, which cannot be related to a single event such as eruption of the overlying basalt lava flow. Major and trace element abundances suggest that the silcretes are formed from quartz sand with little admixture of feldspar and/or clays and that the overlying basalt has contributed nothing to their chemical composition. The evidence is consistent with low‐temperature precipitation of quartz. The significance of the silcrete‐basalt association is considered to be that the basalt acts as a cap rock, providing a confined aquifer within the sand deposit and a favourable environment for SiO2deposition.
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