Himalayan uplift and osmium isotopes in oceans and rivers

Journal Article · Wed Dec 01 04:00:00 EST 1999 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(99)00305-1· OSTI ID:20006268

Sharma, M; Wasserburg, G J; Hofmann, A W; Chakrapani, G J

Previous studies have shown that {sup 187}Os/{sup 188}Os in seawater has become increasingly radiogenic over the last 409 Ma in a manner analogous to strontium. This rapid rise in the marine {sup 187}Os/{sup 188}Os over the last 17 Ma has been attributed to an increase in the bulk silicate weathering rates resulting from the rise of the Himalayas and/or selective weathering and erosion of highly radiogenic organic rich ancient sediments. The key test of this hypothesis is the {sup 187}Os/{sup 188}Os and the total osmium concentration of the Himalayan rivers. The authors report the concentration and isotopic composition of osmium in the Ganges, the Brahmaputra, and the Indus rivers. The {sup 187}Os/{sup 188}Os of the Ganges close to its source (at Kaudiyal) is 2.65 and [Os] = 45 fM/kg. A second sample of the lower reaches of the Ganges at Patna gives {sup 187}Os/{sup 188}Os = 1.59 and [Os] = 171 fM/kg. The {sup 187}Os/{sup 188}Os of the Brahmaputra at Guwahati is 1.07 and [Os] = 52 fM/kg. A sample of the Indus (Besham) has a {sup 187}Os/{sup 188}Os of 1.2 and [Os] = 59 fM/kg. The authors infer that the Himalayas do not provide either a high flow of osmium of a highly radiogenic osmium component to the oceans. The overall trend for osmium and strontium could be explained by a regularly increasing input of global continental weathering sources but the Himalayas themselves appear not to be the dominant source.

• Research Organization: Max-Planck-Inst. fur Chemie, Mainz (DE)
• Sponsoring Organization: US Department of Energy
• DOE Contract Number: FG03-88ER13851
• OSTI ID: 20006268
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 23-24 Vol. 63; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
HIMALAYAS
ISOTOPE RATIO
ORIGIN
OSMIUM ISOTOPES
RIVERS
SEAWATER
WATER CHEMISTRY