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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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TL;DR: The Pennsylvanian sandstones of the Eastern Interior Coal Basin were studied petrographically and stratigraphically to get a better understanding of source areas, sediment transport patterns, and conditions of sedimentation as mentioned in this paper.
Abstract: The Pennsylvanian sandstones of the Eastern Interior Coal Basin were studied petrographically and stratigraphically to get a better understanding of source areas, sediment transport patterns, and conditions of sedimentation. The petrographic study was extended to adjoining basins, the Appalachian, Michigan, and northern Mid-Continent, to obtain a regional picture of mineral composition. Stratigraphic patterns are described in terms of general character, lateral persistence, thickness, and contrasts between channel and sheet sandstones. The sheet sandstones are commonly thinner, finer grained, more argillaceous, and more widely persistent than channel sandstones. In the petrographic study, modal mineralogy, quartz variety, and rough size analyses were made of 176 samples and heavy minerals were estimated from 35 samples. The sandstones fall into three petrographic types that correlate with stratigraphic position: orthoquartzites in the basal zone (Caseyville Group), types intermediate between orthoquartzites and subgraywackes in the next higher zone (lower Tradewater Group) and subgraywackes in all higher groups. Although there are minor differences in composition bet een geographic provinces, the major aspect is one of homogeneity over the entire area of the northcentral and northeastern states. Current intensity, the primary factor in sedimentation conditions, varied greatly both locally and regionally, but the range of variability was more or less homogeneous throughout the stratigraphic section and in all of the geographic provinces. Conflicting evidence on marine or nonmarine origin of the sandstones is harmonized, to infer deposition in a combination of a variety of shallow water marine, deltaic, and coastal plain environments. Source areas and patterns of movement of detritus to sedimentary basins were largely inherited from early Pennsylvanian time. After Caseyville time, detritus from the east and northeast moved over the entire basin of deposition, vastly diluting material derived from the north and northwest. Continued mild erosion of source areas throughout Pennsyl anian time led to gradual but incomplete removal of a sedimentary cover and to the exposure of limited areas of igneous and metamorphic rocks.

35 citations

Journal ArticleDOI
TL;DR: The Honghai VMS Cu-Zn deposit is located in the Dananhu-Tousuquan arc, Eastern Tianshan, northwestern China as mentioned in this paper, and detailed drill core logging, petrographic study and electron microprobe analyses had delineated six alteration/mineralization zones.

35 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the change in sediment composition in the Shikoku Basin during the Quaternary and Pleistocene stages of the Nankai Trough.
Abstract: Abstract Submarine slope systems in subduction zones evolve in response to a combination of tectonic and sedimentary forcing. It can be difficult to determine how and when tectonic forcing affects sedimentation, especially when investigating ancient rock successions, but one of the more reliable indicators is a change in sediment composition. During Leg 190 of the Ocean Drilling Program, sandy turbidites were recovered from a Quaternary trench wedge (Nankai Trough), a Pliocene-Pleistocene slope basin, the underlying Pliocene-Miocene accretionary prism, and a Miocene turbidite facies in the Shikoku Basin. Differences in detrital provenance between the sand and clay-sized fractions indicate that turbidity currents did not follow pathways of suspended-sediment transport during the past 10 Ma. During the middle and late Miocene, the sand probably was eroded from a newly exposed accretionary complex (Shimanto Belt). In contrast, high contents of detrital smectite in Miocene mudstones (>50 wt% of the <2 μm size fraction, relative to illite, chlorite + kaolinite, and quartz) point to a strong volcanic component of suspended-sediment input (Izu-Bonin island arc). The sand in accreted Pliocene turbidites was also eroded from the Shimanto Belt and transported by transverse flow down the insular slope. The trench-wedge facies then switched to axial flow during the Quaternary, when the sand supply tapped a mixed volcanic-metasedimentary provenance in the rapidly uplifted Izu-Honshu collision zone. Progressive depletion of smectite during the Pliocene and Pleistocene (<20 wt%) points to increased movement of illite- and chlorite-rich clay toward the east and NE from sources on Kyushu and Shikoku. That shift in mud composition coincides with intensification of the North Pacific western boundary current (Kuroshio Current) at approximately 3 Ma. Overall, the depositional system in the Nankai Trough and Shikoku Basin shifted its sand sources because of regional tectonics, whereas the suspended-sediment budget was modulated by hemispheric changes in ocean-water circulation.

35 citations

Journal ArticleDOI
TL;DR: In this paper, the authors show that the Torlesse terrane rocks are more siliceous and contain abundant granitic debris, whereas the Waipapa terrane is considerably less dense, and typical sandstones have a high content of intermediate volcanic clasts.
Abstract: Greywacke-type basement rocks from tunnels and other excavations along the western part of the Kaimanawa Range (eastern diversions) and in a buried sequence cut by the Whakapapa-Tawhitikuri tunnel (western diversions) comprise mainly sandstone, siltstone, and argillite, but chert and minor basaltic rock and limestone are also present in the Kaimanawa Range. Rocks of the latter are comparable with Torlesse terrane sequences elsewhere, whereas the Whakapapa-Tawhitikuri tunnel rocks have contrasting petrography and structural style and belong to the younger Waipapa terrane, forming part of the Morrinsville facies. Petrographic, modal, and chemical data show that the Torlesse rocks are more siliceous and contain abundant granitic debris; the Waipapa terrane rocks are considerably less siliceous, and typical sandstones have a high content of intermediate volcanic clasts. Among the Kaimanawa Range rocks, complexly intermixed units, involving sandstone, siltstone, argillite, and chert, approach typical ...

35 citations

Journal ArticleDOI
TL;DR: In this article, the saturation state of the other minerals of the matrix can be discussed according to these constraints, and a method capable of reconstructing consistent compositions of diagenetic waters is presented.

35 citations


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