Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks

Kandasamy, Selvaraj; Chen, Chen‐Tung Arthur

doi:10.1086/498102

Cited by 192 publications

(95 citation statements)

References 54 publications

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“…All the samples analyzed here plot parallel to the A-CN line (Figure 13), defining a nonsteady-state weathering trend towards the "CN" apex, which is probably due to the presence of diagenetic calcite cement rather than Na-rich feldspar. This nonsteady-state weathering indicates balanced rates of chemical weathering and erosion, which produces compositionally similar sediments over a long period (Nesbitt et al, 1997;Selvaraj and Chen, 2006). The result supports the conclusion that the sandstones of the Hawkesbury Sandstone Formation were derived from granitic to granodiorite source terrain ( Figure 13).…”

Section: Source Area Weatheringsupporting

confidence: 78%

Provenance, diagenesis, tectonic setting, and geochemistry of Hawkesbury Sandstone (Middle Triassic), southern Sydney Basin, Australia

Zaid¹,

Gahtani²

2015

Turkish J Earth Sci

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The Hawkesbury Sandstone is an important groundwater reservoir in the southern part of the Sydney Basin, Australia. However, its diagenesis and provenance and its impact in reservoir quality are virtually unknown. The present study aims to reconstruct the parent rock assemblages of the Hawkesbury Sandstone, their tectonic provenance, and the physiographic conditions under which these sediments were deposited. Samples from the EAW 18a and EDEN 115 field representing the Middle Triassic Hawkesbury Sandstone were studied using a combination of petrographic, mineralogical, and geochemical techniques. The Hawkesbury Sandstone is yellowish brown in color, siliceous, and partly calcareous; it originated as sands were deposited in fluvial channels. Texturally, Hawkesbury Sandstone is medium-to coarse-grained, mature, and moderately well sorted. Scarcity of feldspars indicates that the rock is extensively recycled from a distant source. Hawkesbury Sandstone has an average framework composition of Q 92.07 F 0.31 R 7.62 , and 95.9% of the quartz grains are monocrystalline. The Hawkesbury Sandstone is mostly quartz arenites with subordinate sublithic arenites, and bulk-rock geochemistry supports the petrographic results. Petrographic and geochemical data of the sandstones indicate that they were derived from craton interior to quartzose recycled sedimentary rocks and deposited in a passive continental margin of a syn-rift basin. The cratonic Lachlan Orogen is the main source of Hawkesbury Sandstone. The chemical index of alteration, plagioclase index of alteration, and chemical index of weathering values (3.41-87.03) of the Hawkesbury Sandstone indicate low-moderate to high weathering, either of the original source or during transport before deposition, and may reflect low-relief and humid climatic conditions in the source area. Diagenetic features include compaction: kaolinite, silica, mixed-layer clays, siderite, illite, and ankerite cementation with minor iron-oxide, dolomite, chlorite, and calcite cements. Silica dissolution, grain replacement, and carbonate dissolution greatly enhance the petrophysical properties of many sandstone samples.

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Section: Source Area Weatheringsupporting

confidence: 78%

Provenance, diagenesis, tectonic setting, and geochemistry of Hawkesbury Sandstone (Middle Triassic), southern Sydney Basin, Australia

Zaid¹,

Gahtani²

2015

Turkish J Earth Sci

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“…At the same time, high topographies, frequent seismic and typhoon activities, and related storm-triggered landslides leave the surface rocks with insufficient time to undergo chemical weathering. Therefore, relatively high physical versus chemical denudation rates occur on this oceanic island [24]. The clay mineral assemblages in Taiwan are determined by the composition of the bedrock.…”

Section: Figurementioning

confidence: 99%

Clay mineral composition and their sources for the fluvial sediments of Taiwanese rivers

Shi

Kao³

et al. 2011

Chin. Sci. Bull.

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Located at the collision boundary between the Philippine Sea Plate and the Eurasian Continental Plate, the island of Taiwan is generally recognized as an important example in the MARGINS Program Science Plan and "source-to-sink" research because of its high tectonic activity, heavy rainfall and unique geography. Large suspended sediment loads are transported to the adjacent ocean by Taiwanese rivers every year, making Taiwan an important source of sediments into the adjacent seas and a natural laboratory for studying the systemic movement of fluvial sediments from source to sink. A detailed study on the clay mineral composition of surface sediments collected from the drainage basins of 12 Taiwanese rivers using X-ray diffraction methods was conducted. Our results indicated that the clay mineral assemblages consisted dominantly of illite (approximately 73%) and chlorite (approximately 24%), with lesser abundances of kaolinite (approximately 3%) and even lower levels of smectite from the Danshuei River sediments in northwestern Taiwan. The Jhuoshuei River sediments from western Taiwan contained clay mineral assemblages that consisted of illite (approximately 75%) and chlorite (approximately 25%), but they lacked kaolinite and smectite. In southwestern Taiwan, the clay mineral assemblages were dominated by illite (approximately 75%) and chlorite (approximately 23%), but had a low abundance of kaolinite (generally < 2%) and no smectite. The clay mineral assemblages in eastern Taiwan are obviously different from those in western parts of the island. The most noticeable difference is that the average abundance of chlorite in the Hualien River from eastern Taiwan was the highest (approximately 48%) of all the Taiwanese rivers. We concluded that, in general, the clay mineral assemblages in Taiwanese rivers were mainly composed of illite and chlorite with kaolinite and smectite being scarce, and these trends are different from those in China's mainland rivers. The clay mineral composition shown in this study was primarily determined by the properties of the bedrock, and the differential weathering intensities of the drainage area. The surface sediments in Taiwan's rivers showed a greater abundance of illite and chlorite because the outcropped rocks were mainly composed of Tertiary sedimentary rocks, especially sandstone, shale and slate, and show strong physical weathering. The relatively high relief and more abundant rainfall also caused the clay minerals in the fluvial sediments to be transported to the estuaries down rivers from the mountains and then delivered to the adjacent seas by currents and waves over a shorter time scale.

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“…For example, although rivers surrounding Taiwan (Choshui, Tsengwen, Kaoping, Peinan, Hsuikuluan, and Hualien) have small drainage areas, their physical erosion rate (average 1365 mg cm −2 a −1 ) may be the highest in the world and discharge 185×10 6 t suspended sediments annually [25] . The rainstorm was reported as the most important forcing factor of denudation in Taiwan [37] . But the situation of mountains in Middle Vietnam is quite different.…”

Section: Source Analysis Of Clay Mineralsmentioning

confidence: 99%

Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution

Liu

Zhao

et al. 2007

SCI CHINA SER D

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High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are reported to reconstruct a history of East Asian monsoon evolution. Variations in Illite, chlorite, and kaolinite contents indicate a strong glacial-interglacial cyclicity, while changes in smectite content present a higher frequency cyclicity. The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea. Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands. Illite and chlorite originated mainly from the Mekong and Red rivers. Kaolinite was provided mainly by the Pearl River. Spectral analysis of the kaolinite/(illite+chlorite) ratio displays a strong eccentricity period of 100 ka, implying the ice sheet-forced winter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka, and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well, implying the tropical-forced summer monsoon evolution. The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity, with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere, with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation. The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons, respectively, implying their diplex and self-contained forcing mechanism. clay minerals, provenance, East Asian monsoon, late Quaternary, Middle Vietnam, South China SeaThe East Asian monsoon is a significant component of the global climate. It dominates seasonal patterns of winds, precipitation and runoff, and determines the character of land vegetation over East Asia [1] . The South China Sea, the largest marginal sea in the western Pacific, is characterized by anticlockwise surface currents forced by northeasterly winds in winter, and in contrast, by southwesterly surface currents forced by southwesterly winds in summer. The South China Sea received products of chemical weathering and physical erosion occurred in adjacent continents [2] . Among them, as the most important detrital materials of terrigenous origin in the abyssal South China Sea, clay minerals can be used to track oceanic current variations and to reveal contemporaneous paleoclimatic changes prevailing in con-

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Moderate Chemical Weathering of Subtropical Taiwan: Constraints from Solid‐Phase Geochemistry of Sediments and Sedimentary Rocks

Cited by 192 publications

References 54 publications

Provenance, diagenesis, tectonic setting, and geochemistry of Hawkesbury Sandstone (Middle Triassic), southern Sydney Basin, Australia

Provenance, diagenesis, tectonic setting, and geochemistry of Hawkesbury Sandstone (Middle Triassic), southern Sydney Basin, Australia

Clay mineral composition and their sources for the fluvial sediments of Taiwanese rivers

Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution

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