Petrographic, geochemical, and textural analyses of interbedded gypsum and Cu-ore deposits in the Upper Miocene Boleo Formation, Baja California Sur, México

The Upper Miocene Boleo Formation of the Santa Rosalía Basin in Baja California Sur, México, records the evolution of evaporite basin environments, hydrothermal mineralization, and diagenetic mobilization within a rift setting. Interbedded gypsum, siliciclastic, and metalliferous clay-rich facies within the DDB10 core reflect shifts between semi-restricted marine and subaerial sabkha environments. A gypsum accumulation rate of ~0.32 mm/yr in the Lower DDB10 Section reflects slow deposition influenced by marine restriction, clastic input, and hydrothermal activity. Geochemical and petrographic analyses indicate structurally controlled, multi-stage mineralization from hydrothermal and hydrogenous sources. Stable isotope values δ¹⁸OVSMOW and δ³⁴SVCDT reflect fluid mixing, diagenetic overprint, and a consistent marine sulfate source. The occurrence of both primary and secondary gypsum, together with residual anhydrite, provides evidence for burial followed by uplift, while the position of stylolites within the core indicates shallow burial depths. During uplift, meteoric fluids infiltrated fractures, resulting in clay alteration, precipitation of oxide minerals, and rehydration of anhydrite to gypsum. These findings reflect a synsedimentary-syndiagenetic depositional model influenced by fluid–rock interaction, brine evolution, and diagenetic processes.

Name thesis:degree_name

M.S. (Master of Science)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Environmental and Urban Geosciences (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2026

Author dc:creator

• Klene, Mary Jean

Advisor dc:contributor.advisor

• Niemi, Tina M.

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/10355/112333

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/112333