Weathering indices for rhyolitic tuff and granite in Hong Kong

Guan, Peng; Ng, Charles Wang Wai; Sun, Manping; Tang, Wilson H.

doi:10.1016/s0013-7952(00)00071-5

Cited by 56 publications

(26 citation statements)

References 20 publications

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“…Consequently, chemical weathering may have a great influence on the compositional deviation of weathered material from residual parent rocks. Previous studies revealed that alkaline and alkaline earth elements including Na, Ca, Mg, and K can be considerably leached from weathered materials in Hong Kong (Sewell, 1999;Fyfe et al, 2000;Guan et al, 2001), and even ferrous iron and silicon can be attacked during intense chemical weathering (Guan et al, 2001). In addition, the sediment from the inner shelf of Hong Kong may be readily contaminated from agriculture, industry, sewage treatment, domestic sources and illegal dumping of materials since Hong Kong is highly developed and densely populated in coastal areas (Yim and Fung, 1981;Yim and Leung, 1987;Sewell, 1999;Tanner et al, 2000;Li et al, 2000Li et al, , 2001Zhou et al, 2004).…”

Section: Provenance Discrimination Of the Borehole Bh2 Sedimentsmentioning

confidence: 99%

Geochemical composition of inner shelf Quaternary sediments in the northern South China Sea with implications for provenance discrimination and paleoenvironmental reconstruction

Yang

Yim

Huang

2008

Global and Planetary Change

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Section: Provenance Discrimination Of the Borehole Bh2 Sedimentsmentioning

confidence: 99%

Geochemical composition of inner shelf Quaternary sediments in the northern South China Sea with implications for provenance discrimination and paleoenvironmental reconstruction

Yang

Yim

Huang

2008

Global and Planetary Change

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“…In the case of granite weathering, physical and chemical weathering are the primary focus (Guan et al 2001;Ceryan et al 2008). Physical and chemical weathering mostly act together: the progress of chemical weathering usually relying on fractures opened or formed partly as a result of physical weathering (Irfan 1996).…”

Section: Weathering Mechanism Of Granitementioning

confidence: 99%

“…Several studies have proposed quantitative indices of the weathering degree and examined its correlations with engineering characteristics (Tugrul and Gurpinar 1997;Guan et al 2001;Duzgoren-Aydin et al 2002;Son et al 2010;Regmi et al 2014). Of the various engineering characteristics of the decomposed granite layer, shear wave velocity (V S ) is determined through in situ seismic tests.…”

Section: Introductionmentioning

confidence: 99%

Geotechnical comparison of weathering degree and shear wave velocity in the decomposed granite layer in Hongseong, South Korea

et al. 2015

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As part of a fundamental characterization of a subsurface layer in South Korea, the weathering degree and shear wave velocity (V S ) were evaluated in a decomposed granite in Hongseong, using X-ray fluorescence analyses and site investigations, including borehole drilling with standard penetration test (SPT) and in situ seismic tests. The subsurface layer was composed of a weathered layer 10-40 m thick at most sites. Weathering degree analyses indicated that three chemical weathering indices, the modified weathering potential index (MWPI), Vogt ratio (VR), and weathering index of Parker (WIP), generally increased with decreasing depth. In situ seismic tests revealed that V S ranged between 200 and 500 m/s in the weathered layer. Using the V S and N values from the SPT at borehole seismic testing sites, correlations between V S and N values were established for the weathered layer. Furthermore, examination of the relationships of the V S and N values with the MWPI, WIP, and 100/VR indices showed that the index values increased linearly with increasing V S and exponentially with increasing N values.

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“…Plutonic igneous rocks formed at great depths are initially composed of crystalline minerals that are unstable at surface pressures and temperatures, which readily weather to secondary, more stable minerals such as clays. The proportion of secondary minerals within an igneous rock increases proportionally with the degree of weathering; however, as secondary minerals are significantly weaker than primary crystalline minerals, civil engineering projects undertaken on highly weathered rocks are extremely hazardous [1][2][3][4][5]. As such, quantification of the degree of weathering is critical in order to evaluate ground stability before infrastructure development [4,5].…”

Section: Introductionmentioning

confidence: 99%

A preliminary study on the new geotechnical weathering index in the evaluation of altered biotite granite

Choi¹,

Oh²,

Lee³

et al. 2018

IJET

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The existing chemical index of alteration has a difficulty to evaluate the degree of weathering in biotite granites due to an assumption that K2O content decreases along with Na2O, CaO, and MgO. We found that relative K2O content increases during weathering of biotite granite, as it is retained within such rocks due to (1) the chemical and physical stability of K-feldspar and (2) the formation of illite via incorporation of K ions released from biotite. The calculated ranges of most chemical indexes for biotite granite weathering do not show a good correlation with the weathering grade except the CIW, WIP and V indexes. The range of the CIW, WIP and V indexes according to the weathering grade were very small, and thus small errors in whole-rock chemical analyses can produce large discrepancies in calculated values. Further, the WPI index is a relative weathering index that depends on the composition of a fresh standard sample and cannot be applied to determine the absolute degree of weathering in granites if no protolith is available. We suggest a new weathering index (BWI; Biotite weathering index) based on a decrease in the number of K ions in the interlayer site of biotite during weathering of granite.Newly calculated values show a much wider range than the CIW, WIP and V indexes with a good relationship with a weathering grade. Therefore, it is necessary to establish the new index for a detailed classification of weathering degree.

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Weathering indices for rhyolitic tuff and granite in Hong Kong

Cited by 56 publications

References 20 publications

Geochemical composition of inner shelf Quaternary sediments in the northern South China Sea with implications for provenance discrimination and paleoenvironmental reconstruction

Geochemical composition of inner shelf Quaternary sediments in the northern South China Sea with implications for provenance discrimination and paleoenvironmental reconstruction

Geotechnical comparison of weathering degree and shear wave velocity in the decomposed granite layer in Hongseong, South Korea

A preliminary study on the new geotechnical weathering index in the evaluation of altered biotite granite

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