Back to Search
Start Over
Mineralogy and geochemistry of the Holocene lacustrine sediments in Nam Co, Tibet
- Source :
-
Quaternary International . Aug2008, Vol. 187 Issue 1, p105-116. 12p. - Publication Year :
- 2008
-
Abstract
- Abstract: The carbonates, clays and major chemical compositions of lacustrine sediments in Nam Co (Lake) were examined by X-ray diffraction, scanning electron microscopy and chemical analysis. Carbonates include monohydrocalcite (MHC, first report from China and in a high-altitude lake), low-Mg calcite and traces of dolomite. MHC in Nam Co is developed in water (1.8g/L) with high Mg/Ca molar ratios (10.03–15.03), high pH (8.04–9.72) and the presence of bacteria, algae, diatom and ostracoda. Illite and Mg-chlorite provide a strong evidence for physical weathering in the Holocene. Most Ca and Sr in sediments originate from carbonates as the molar ratios of Ca and CO3 2− are all less than 1 and the curve of Sr is very similar to that of Ca. However, most of the Mg, Fe and Rb are from clays. The lake water shifted from a fresh water environment to an evaporative, alkaline environment by 2.06cal.kaBP. There was a depositional event that the depositional rate changed from 0.134 to 1.639mm/a at about 2cal.kaBP. [Copyright &y& Elsevier]
- Subjects :
- *PHYSICAL geology
*ROCK-forming minerals
*MINERALOGY
*HYDROGEN-ion concentration
Subjects
Details
- Language :
- English
- ISSN :
- 10406182
- Volume :
- 187
- Issue :
- 1
- Database :
- Academic Search Index
- Journal :
- Quaternary International
- Publication Type :
- Academic Journal
- Accession number :
- 33344130
- Full Text :
- https://doi.org/10.1016/j.quaint.2007.12.008