Geochemistry of the Triassic–Jurassic lateritic bauxites of the Salt Range

Autor(en)

Shahid Iqbal, Mehwish Bibi, Michael Wagreich

Abstrakt

Bauxite deposits are residuals of intense lateritic weathering under warm and humid palaeoclimates. The Triassic–Jurassic Boundary (TJB) interval in the Salt Range, Pakistan, provides one such case of bauxite deposits formation along the SW tropical Neo-Tethyan passive margin. Thick, red bauxites/bauxitic clays occur at the contact of the Upper Triassic Kingriali Formation and the Lower Jurassic Datta Formation. These bauxites are rich in kaolinite, haematite, boehmite (Al₂O₃ and Fe₂O₃), and are depleted in silica (SiO₂). Geochemical proxies of the succession signal intense chemical weathering of the parent siliciclastics under Mesozoic “greenhouse” conditions. Certain trace elements and Rare Earth Elements (REEs) are enriched up to seven times compared to mean Upper Continental Crust (UCC) values. These bauxites are synchronous with the Amir-Abad bauxites of the Alborz Mountains, central Iranian Plateau, that occur between the thick Triassic dolomite/dolomitic limestones of the Elika Formation and the Lower Jurassic Shemshak Formation. Thus, the Salt Range, Pakistan, provides evidence for the eastward extension of the Irano-Himalayan bauxites that are extended westward into Mediterranean bauxites, and the western Tethys by correlation with European bauxites. The TJB bauxites in the Salt Range support increased chemical weathering on the SW Neo-Tethyan passive margin and correspond to an associated sea-level fall during this time interval. This supports the Neo-Tethyan tectonics contribution in the formation of bauxite deposits during the Triassic–Jurassic in addition to the widely studied karst-bauxites that formed in response to the subduction and orogenic processes in the Paleo-Tethys.

Organisation(en)

Institut für Geologie

Externe Organisation(en)

Hebrew University Jerusalem, Quaid-i-Azam University

Journal

International Journal of Earth Sciences

Band

112

Seiten

1527-1552

Anzahl der Seiten

26

ISSN

1437-3254

DOI

https://doi.org/10.1007/s00531-023-02310-9

Publikationsdatum

07-2023

Peer-reviewed

Ja

ÖFOS 2012

105105 Geochemie, 105121 Sedimentologie

Schlagwörter

ASJC Scopus Sachgebiete

Allgemeine Erdkunde und Planetologie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/ebbc76a7-7080-4957-a489-3efa3cfd30c4