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Petrography

About: Petrography is a research topic. Over the lifetime, 7449 publications have been published within this topic receiving 102018 citations.


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01 Jan 1991
TL;DR: In this article, five new fragments of quartz monzodiorite (QMD) were identified in particles from soil 15403, which was collected from the boulder sampled as rock 15405, an impact-melt breccia containing clasts of KREEP basalt, QMD, granite, and a more primitive alkali norite.
Abstract: Five new fragments of quartz monzodiorite (QMD) were identified in particles from soil 15403, which was collected from the boulder sampled as rock 15405, an impact-melt breccia containing clasts of KREEP basalt, QMD, granite, and a more primitive alkali norite. Petrographic and geochemical studies of the fragments show considerable variation in modal proportions and bulk composition. This heterogeneity is due to unrepresentative sampling in small fragments of coarse-grained rocks. Variations in the proportions of accessory minerals have marked effects on incompatible-trace-element concentrations and ratios. Semiquantitative calculations support the derivation of QMD from 60-percent fractional crystallization of a KREEP basalt magma as suggested by Hess (1989). Apollo 15 KREEP basalt cannot be the actual parent magma because the evolved rocks predate volcanic KREEP basalts. It is suggested that ancient KREEP basalt magmas have crystallized as plutons, with alkali norite clasts offering the only direct evidence of this precursor.

32 citations

Journal ArticleDOI
TL;DR: This article used whole-rock and mineral elemental compositions along with standard and cathodoluminescence petrography to characterize alteration histories of Late Triassic to Middle Jurassic metavolcanic rocks in the Ritter Range, White-Inyo Mountains, and Alabama Hills.
Abstract: Volcanic and plutonic rocks exposed in east-central California record a long history of metasomatism and/or metamorphism within the Mesozoic Cordilleran continental arc. We use whole-rock and mineral elemental compositions, along with standard and cathodoluminescence petrography to characterize alteration histories of Late Triassic to Middle Jurassic metavolcanic rocks in the Ritter Range, White-Inyo Mountains, and Alabama Hills. Although alkali-metasomatism is widespread and pervasive, ratios and abundances of Ce, Th, Tb, and Ta suggest that mafic protoliths from the White-Inyo Mountains were shoshonitic, whereas those from the Ritter Range were calc-alkaline. Alkali exchange apparently modified the compositions of many metavolcanic rocks. Much of this metasomatism may have occurred at low-temperature (T) conditions, and attended or shortly postdated deposition of the volcanic protoliths. High δ 18 O values for K-rich metatuffs from

32 citations

Journal ArticleDOI
TL;DR: The Phra Wihan Formation as discussed by the authors is a sedimentary sequence from the western flank of the Khorat Plateau, Thailand, which is high in silica (SiO2 67-98 wt.

31 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used the evaporation of single zircon grains from two metasedimentary units from opposite sides of the New England Appalachians in the USA to determine their ages.

31 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023551
20221,098
2021370
2020344
2019310
2018291