Purplish soils having high fertility with mineral nutrients inherited from the parent rock are widely distributed in the hills along the Yangtze River,especially in the Sichuan Basin.Pot and field weathering experimen...Purplish soils having high fertility with mineral nutrients inherited from the parent rock are widely distributed in the hills along the Yangtze River,especially in the Sichuan Basin.Pot and field weathering experiments were conducted to mimic rock weathering and nutrient release processes in order to better understand soil fertility and nutrient compensation. Three types of purplish rock formations formed in the Jurassic period,Shaximiao(J_2s),Suining(J_3s),and Penglaizhen (J_3p),as well as one type formed in the Cretaceous period,the Chengqiangyan group(K_1c),were used in this study. Results showed that the soil formation rate was in the range from 11.2 to 19.6 mm every year,and rock weathering was in the order of J_3s>J_3p>J_2s>K_1c.Because more rock surface was exposed to sunlight and rainfall in field conditions,pot weathering was slower than field weathering.Nutrient release rates increased with rock weathering and was in the order similar to that of rock weathering:J_3p>J_3s>J_2s>K_1c.Potassium release was the most important in all rocks;after 2 years of weathering,19.4% to 46.9% of K was released from the initial parent rocks,which suggested that K release from weathering could meet most of the crop K requirement in purplish soils.Thus,rapid release of nutrients from weathering of purplish rocks was key to nutrient replenishment and fertility of purplish soils.展开更多
Weathered clastic crust can be subdivided into weathered clay and leached zone in terms of variable weathering of different minerals and mobility of weathered products.On the basis of clastic outcrops and well cores i...Weathered clastic crust can be subdivided into weathered clay and leached zone in terms of variable weathering of different minerals and mobility of weathered products.On the basis of clastic outcrops and well cores in the Junggar Basin,the dark red Fe-rich weathered clay is formed in an arid environment,whereas the light blue Al-rich weathered clay under humid conditions.According to the geochemical analysis,a new weathering index for weathered clastic crust is built mainly on Fe and Al contents,accurately indicating the weathered clay,sandy leached zone,and muddy leached zone in the Junggar Basin.The breaking pressure of weathered clay is rather large,the same as that of normal muddy cap,effectively to seal oil or gas.The porosity of underlying leached zone is greatly enhanced by weathering and leaching,but its permeability is a function of clay mineral content,i.e.,the higher the clay content,the worse the permeability.Weathered crust provides effective sealing conditions for both top and bottom layers of a petroleum reservoir,and is important in the clastic hydrocarbon exploration.展开更多
基金the National Basic Research Program of China(No.2003CB415202)the National Natural Science Foundation of China(Nos.40571093 and 49601009)
文摘Purplish soils having high fertility with mineral nutrients inherited from the parent rock are widely distributed in the hills along the Yangtze River,especially in the Sichuan Basin.Pot and field weathering experiments were conducted to mimic rock weathering and nutrient release processes in order to better understand soil fertility and nutrient compensation. Three types of purplish rock formations formed in the Jurassic period,Shaximiao(J_2s),Suining(J_3s),and Penglaizhen (J_3p),as well as one type formed in the Cretaceous period,the Chengqiangyan group(K_1c),were used in this study. Results showed that the soil formation rate was in the range from 11.2 to 19.6 mm every year,and rock weathering was in the order of J_3s>J_3p>J_2s>K_1c.Because more rock surface was exposed to sunlight and rainfall in field conditions,pot weathering was slower than field weathering.Nutrient release rates increased with rock weathering and was in the order similar to that of rock weathering:J_3p>J_3s>J_2s>K_1c.Potassium release was the most important in all rocks;after 2 years of weathering,19.4% to 46.9% of K was released from the initial parent rocks,which suggested that K release from weathering could meet most of the crop K requirement in purplish soils.Thus,rapid release of nutrients from weathering of purplish rocks was key to nutrient replenishment and fertility of purplish soils.
基金supported by National Science and Technology Major Projects(Grant No.2011ZX05001-003)
文摘Weathered clastic crust can be subdivided into weathered clay and leached zone in terms of variable weathering of different minerals and mobility of weathered products.On the basis of clastic outcrops and well cores in the Junggar Basin,the dark red Fe-rich weathered clay is formed in an arid environment,whereas the light blue Al-rich weathered clay under humid conditions.According to the geochemical analysis,a new weathering index for weathered clastic crust is built mainly on Fe and Al contents,accurately indicating the weathered clay,sandy leached zone,and muddy leached zone in the Junggar Basin.The breaking pressure of weathered clay is rather large,the same as that of normal muddy cap,effectively to seal oil or gas.The porosity of underlying leached zone is greatly enhanced by weathering and leaching,but its permeability is a function of clay mineral content,i.e.,the higher the clay content,the worse the permeability.Weathered crust provides effective sealing conditions for both top and bottom layers of a petroleum reservoir,and is important in the clastic hydrocarbon exploration.
