Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typica...Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typical transitional MORB （T-MORB） variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the product of partial melting at an estimated pressure of - 1 GPa. It is inferred that the magma was subsequently modified at a pressure 〉 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2Os and Na20. There was, however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K20. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cro In addition, the T_JtEE of the magma also increased with fractionation, without any change in （La/Yb）n value.展开更多
Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has th...Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has the potential to reduce the diversity of terrestrial vegetation and associated biota through favouring species adapted to quickly exploiting available nutrients. Although the potential has long been recognised, only recently has enough evidence come together to show beyond reasonable doubt that these changes are already occurring. Linked together, experimental, regional/e.rnpirical, and time-series research provide a powerful argument that enhanced deposition of reactive nitrogen across Great Britain, and potentially the rest of Europe, has resulted in a significant and ongoing decline in grassland species richness and diversity.展开更多
文摘Mid-Ocean Ridge Basalts （MORB） from the Northern Central Indian Ridge （NCIR） were recovered between latitudes 3° and 11° S and are olivine tholeiite with higher abundances of K and Rb. They are of typical transitional MORB （T-MORB） variety and appear to have been generated from an enriched-mantle peridotite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the product of partial melting at an estimated pressure of - 1 GPa. It is inferred that the magma was subsequently modified at a pressure 〉 1 GPa by crystal fractionation and spinel was the first mineral to crystallize followed by separation of relatively Fe-rich olivine with subsequent decrease in pressure. During progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically depleted in MgO, and enriched in ∑FeO, TiO2, P2Os and Na20. There was, however, limited gradual depletion in Al2O3 and CaO and concomitant enrichment in K20. With the progressive fractionation these basalts became gradually enriched in V, Co, Y, Zr and to some extent in Sr, and depleted in Ni and Cro In addition, the T_JtEE of the magma also increased with fractionation, without any change in （La/Yb）n value.
文摘Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has the potential to reduce the diversity of terrestrial vegetation and associated biota through favouring species adapted to quickly exploiting available nutrients. Although the potential has long been recognised, only recently has enough evidence come together to show beyond reasonable doubt that these changes are already occurring. Linked together, experimental, regional/e.rnpirical, and time-series research provide a powerful argument that enhanced deposition of reactive nitrogen across Great Britain, and potentially the rest of Europe, has resulted in a significant and ongoing decline in grassland species richness and diversity.
