Helium isotopes in subsurface fluids from the Baikal Rift Zone: An application to the problems of geodynamics
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| Natura: | Artículo científico |
| Lingua: | en |
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Universidad Nacional Autónoma de México
2002
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| _version_ | 1876455765642838016 |
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| author | B.G. Polyak |
| author_facet | B.G. Polyak |
| contents | Helium isotopes in subsurface fluids from the Baikal Rift Zone: An application to the problems of geodynamics B.G. Polyak Ciencias de la Tierra He isotopes Baikal Lake thermal waters continental rifts The 3He/ 4He = R ratio was studied in underground fluids from 104 sites from the Baikal Rift Zone, BRZ, and adjacent areasin Russia and Mongolia. The R values vary from 1.0×E-8, typical of crustal radiogenic He, up to 1.1×E-5 just below the MORBcharacteristics. The repeated sampling of some sites and the comparison between the data for superficial springs and productiveboreholes have shown no significant R variation in time or in depth.The lowest R values belong to CH4-rich gases. The more diverse R values were measured in N2- and CO2- rich fluids, and thelatter show the highest R. Judging from N2/Aratm ratio, N2-rich gases are of atmospheric origin. The fN2/fNe ratio value in CO2- richfluids indicates the excess (non-atmospheric) nitrogen. The comparison of the R values with He concentrations and predominatecomponents of a fluid gas phase shows that this phase is formed under the effect of solubility-controlled fractionation in gaswatersystem and a gain/loss of chemically active gases within the crust.The distribution of R values across the BRZ strike indicates a discharge of heat-mass flux from the mantle not only inside theBRZ but also far to the east. Inside the BRZ, the range of R values is widest: from 4.9×E-8 to 1.1×E-5. These variations areregular: R values diminish along the BRZ strike in both directions from the Tunka Basin considered as a center of rifting. Thedecrease is accompanied by some decay of heat flow density and shows a reduction of heat-mass flux from the mantle in peripheralsegments of the rift zone.The comparison of this trend with the data for other active continental rifts and mid-oceanic ridges suggests radicallydifferent mechanisms of mantle-crust interaction during oceanic spreading and continental rifting. 2002 artículo científico 0016-7169 https://www.redalyc.org/articulo.oa?id=56841420 en http://www.redalyc.org/revista.oa?id=568 Geofísica Internacional application/pdf Universidad Nacional Autónoma de México Geofísica Internacional (México) Num.4 Vol.41 |
| format | Artículo científico |
| id | redalyc_56841420 |
| institution | Redalyc |
| language | en |
| publishDate | 2002 |
| publisher | Universidad Nacional Autónoma de México |
| spellingShingle | Helium isotopes in subsurface fluids from the Baikal Rift Zone: An application to the problems of geodynamics B.G. Polyak Ciencias de la Tierra He isotopes Baikal Lake thermal waters continental rifts Helium isotopes in subsurface fluids from the Baikal Rift Zone: An application to the problems of geodynamics B.G. Polyak Ciencias de la Tierra He isotopes Baikal Lake thermal waters continental rifts The 3He/ 4He = R ratio was studied in underground fluids from 104 sites from the Baikal Rift Zone, BRZ, and adjacent areasin Russia and Mongolia. The R values vary from 1.0×E-8, typical of crustal radiogenic He, up to 1.1×E-5 just below the MORBcharacteristics. The repeated sampling of some sites and the comparison between the data for superficial springs and productiveboreholes have shown no significant R variation in time or in depth.The lowest R values belong to CH4-rich gases. The more diverse R values were measured in N2- and CO2- rich fluids, and thelatter show the highest R. Judging from N2/Aratm ratio, N2-rich gases are of atmospheric origin. The fN2/fNe ratio value in CO2- richfluids indicates the excess (non-atmospheric) nitrogen. The comparison of the R values with He concentrations and predominatecomponents of a fluid gas phase shows that this phase is formed under the effect of solubility-controlled fractionation in gaswatersystem and a gain/loss of chemically active gases within the crust.The distribution of R values across the BRZ strike indicates a discharge of heat-mass flux from the mantle not only inside theBRZ but also far to the east. Inside the BRZ, the range of R values is widest: from 4.9×E-8 to 1.1×E-5. These variations areregular: R values diminish along the BRZ strike in both directions from the Tunka Basin considered as a center of rifting. Thedecrease is accompanied by some decay of heat flow density and shows a reduction of heat-mass flux from the mantle in peripheralsegments of the rift zone.The comparison of this trend with the data for other active continental rifts and mid-oceanic ridges suggests radicallydifferent mechanisms of mantle-crust interaction during oceanic spreading and continental rifting. 2002 artículo científico 0016-7169 https://www.redalyc.org/articulo.oa?id=56841420 en http://www.redalyc.org/revista.oa?id=568 Geofísica Internacional application/pdf Universidad Nacional Autónoma de México Geofísica Internacional (México) Num.4 Vol.41 |
| title | Helium isotopes in subsurface fluids from the Baikal Rift Zone: An application to the problems of geodynamics |
| topic | Ciencias de la Tierra He isotopes Baikal Lake thermal waters continental rifts |
| url | https://www.redalyc.org/articulo.oa?id=56841420 |