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Journal Article
Journal: GSA Bulletin
Published: 11 May 2021
GSA Bulletin (2022) 134 (1-2): 348–370.
...). The outstanding character of RSS3-Ia is related to the silica cemented mudstones and chert revealed in the lithology, and the above average Si/Ti ratios in cores recovered at Site U1521 ( McKay et al., 2019 ). The opal content of RSS3-Ia is inferred to be related to the diagenetic alteration of diatom-bearing...
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Journal Article
Journal: AAPG Bulletin
Published: 15 February 2021
AAPG Bulletin (2021) 105 (2): 391–436.
...David K. Larue; Christian Hager; Thomas Merrifield; Gena M. Evola; David Crane; Phillip Yorgensen ABSTRACT Unconventional opal-A and opal-CT diatomaceous reservoirs in the Monterey Formation of the San Joaquin Valley in California have produced for more than 30 yr. These opal-A reservoirs...
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Journal Article
Published: 28 October 2020
Journal of Sedimentary Research (2020) 90 (9): 1037–1067.
...Shahab Varkouhi; Nicholas J. Tosca; Joseph A. Cartwright ABSTRACT Silica diagenesis leads to dramatic petrophysical variations in the host sediment across the depth of an opal-A to opal-CT transition zone. Predicting the present-day diagenetic status of opal-A to opal-CT transition zones, i.e...
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Journal Article
Published: 08 April 2020
The Canadian Mineralogist (2020) 58 (2): 231–246.
...Dereje Ayalew; Raphael Pik; Sally Gibson; Gezahegn Yirgu; Seid Ali; Dereje Assefa ABSTRACT Opals are widespread within Miocene volcanic sequences in the North Shoa province of Central Ethiopia. The opal occurs as cavity fillings in a 5 m thick seam of glassy rhyolitic ignimbrite that is sandwiched...
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Journal Article
Published: 05 February 2020
Mineralogical Magazine (2020) 84 (2): 343–354.
... colours that cause fiery effects to be observed on their characteristic brown base. The specific morphology of poorly ordered chalcedony (crystallinity index = 0.1–1.5) with an admixture of mogánite (av. 6.6%), micro-quartz and opal-C forming a colloform texture seems to be responsible for the presence...
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