The Cenozoic evolution of the strontium and carbon cycles: Relative importance of continental erosion and mantle exchanges

被引:82
作者
Godderis, Y
Francois, LM
机构
[1] Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, B-4000 Liège
关键词
D O I
10.1016/0009-2541(95)00117-3
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The past variations of the seawater Sr-87/Sr-86 isotopic ratio are related to changes in the relative contribution of the mantle Sr input to the ocean and the Sr supply from continental weathering. Recently, it has been postulated that the Cenozoic increase in the seawater Sr-87/Sr-86 isotopic ratio was associated with the uplift of the Himalayan and Andean mountains at that time. These orogenies may have changed the Sr isotopic ratio of the continental rocks undergoing weathering (as a result of extensive metamorphism), increased the river flux of Sr through enhanced weathering in these regions and possibly caused the global climatic cooling trend of the Cenozoic. A model of the major geochemical cycles coupled to an energy balance climate model is used to explore the possible causes of the Mesozoic-Cenozoic fluctuations in the seawater Sr-87/Sr-86 isotopic ratio. The contribution of the mantle exchanges at mid-ocean ridges, of the recycling of seafloor carbonates through plate margin volcanism and of the alteration of seafloor basalts to the fluctuations of the seawater Sr-87/Sr-86 isotopic ratio are studied. Finally, this model tentatively describes the impact of the Himalayan orogeny on the geochemical cycles of Sr and C. Some possible effects of the extensive metamorphism associated with the India-Asia collision and of the Himalayan uplift are modelled. The model reproduces the Cenozoic increase of the seawater Sr-87/Sr-86 isotopic ratio. However, the impact of the Himalayan orogeny on the C cycle appears to be limited and insufficient to generate the global climatic cooling of the Cenozoic. Rather, in the model, the Cenozoic cooling is mostly due to the reduction of the CO2 emission from mid-ocean ridge volcanism and to changes in the chemical weathering rates in the rest of the world excluding the Himalayas.
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页码:169 / 190
页数:22
相关论文
共 58 条
[1]  
[Anonymous], 1987, GLOBAL WATER CYCLE G
[2]  
[Anonymous], 1990, GEOCHEMISTRY SEDIMEN
[3]  
[Anonymous], 1987, HIST EARTHS ATMOSPHE
[4]  
[Anonymous], 1982, TRACERS SEA
[5]  
ARTHUR MA, 1991, GEOL SOC ANN M, pA178
[6]   THE CARBONATE-SILICATE GEOCHEMICAL CYCLE AND ITS EFFECT ON ATMOSPHERIC CARBON-DIOXIDE OVER THE PAST 100 MILLION YEARS [J].
BERNER, RA ;
LASAGA, AC ;
GARRELS, RM .
AMERICAN JOURNAL OF SCIENCE, 1983, 283 (07) :641-683
[7]   A MODEL FOR ATMOSPHERIC CO2 OVER PHANEROZOIC TIME [J].
BERNER, RA .
AMERICAN JOURNAL OF SCIENCE, 1991, 291 (04) :339-376
[8]   CALCULATION OF THE PHANEROZOIC STRONTIUM ISOTOPE RECORD OF THE OCEANS FROM A CARBON-CYCLE MODEL [J].
BERNER, RA ;
RYE, DM .
AMERICAN JOURNAL OF SCIENCE, 1992, 292 (02) :136-148
[9]  
BLATT H, 1975, GEOL SOC AM BULL, V86, P1085, DOI 10.1130/0016-7606(1975)86<1085:POEIMA>2.0.CO
[10]  
2