The Assam-Meghalaya Gneissic Complex(AMGC)of northeast India contains numerous Pan-African granitic bodies that have been attributed to post-collisional rift-related magmatism.The present study is concerned with the f...The Assam-Meghalaya Gneissic Complex(AMGC)of northeast India contains numerous Pan-African granitic bodies that have been attributed to post-collisional rift-related magmatism.The present study is concerned with the first appraisal of intermediate magmatism(diorite,monzonite,and monzodiorite)found in the Borjuri Pluton of Mikir Massif,which is the eastern extension of AMGC.The diorites are strongly metaluminous and exhibit enriched LREE([La/Yb]N=1.63–7.37)with respect to HREE([Gd/Yb]N=1.95–2.27).The studied rocks do not show any mineralogical or textural indication of metamorphism.Tectonic discrimination diagrams indicate that these rocks originated in a within-plate tectonic setting.The lower Mg#(33.49–38.69),low Cr(below detection limit),and Ni(27–41 ppm)contents along with elemental ratios such as Rb/Sr(0.32–0.95),La/Nb(0.49–4.21),and Nb/Ce(0.11–0.64)suggest a crustal source for the diorites.Discrimination diagrams coupled with elemental ratios suggest that these rocks originated due to partial melting of mafic components in the crust with possible contribution from mantle materials.The P–T conditions of diorite emplacement(7.4 kbar,688℃)were calculated using the amphibole-plagioclase geothermobarometer.Geochemical and geochronological data of the Pan-African felsic plutons reported from the AMGC indicate that these rocks were emplaced in a post-collisional extensional regime.The Borjuri Pluton is in close proximity with the Kathalguri Pluton,which has been reported as a product of PanAfrican magmatism.In view of the numerous extensional Pan-African felsic magmatism reported from the AMGC and based on the close vicinity of the Borjuri diorites with the Kathalguri granites,we speculate that the Borjuri diorites are products of the Pan-African post-collisional magmatism.展开更多
The article presents the concept of a network of geoplutonic power plants,the total capacity of which would correspond to the general energy needs of the entire region.A scenario of a regional economy is presented,pro...The article presents the concept of a network of geoplutonic power plants,the total capacity of which would correspond to the general energy needs of the entire region.A scenario of a regional economy is presented,provided with electricity produced from a clean source,without pollutant emissions.Thus,a vision of solving the energy crisis resulting from the planned elimination of fossil energy sources is presented.Such an opportunity appeared after solving the technological problems of deep drilling,exceeding 10 km.The new technology involves extracting heat from HDRs(Hot Dry Rocks)and heating the fluid circulating in a pipe in a closed circuit.The temperature at a depth of 10 km is determined by the regional geothermal gradient.Temperature is in the range of 200-400°C.This is already a zone of degassing magmatic solutions and exothermic chemical reactions.In general,it can be argued that the heat flux density is a function of the distance from magmatic intrusions.展开更多
黑云母是花岗岩常见的暗色矿物之一。黑云母化学成分变化是寄主岩浆固结成岩时不同的物理化学条件下所对应的结果,因此,黑云母化学成分很好地记录了寄主岩浆的属性,对黑云母开展矿物化学成分的研究可以有效地反演寄主岩岩浆演化和成岩...黑云母是花岗岩常见的暗色矿物之一。黑云母化学成分变化是寄主岩浆固结成岩时不同的物理化学条件下所对应的结果,因此,黑云母化学成分很好地记录了寄主岩浆的属性,对黑云母开展矿物化学成分的研究可以有效地反演寄主岩岩浆演化和成岩过程的物理化学条件,指示岩石的成因类型、岩浆物质来源等信息(Wones and Eugster,1965)。展开更多
基金DST-SERB grant vide Project No.CRG/2020/002635CSIR-JRF fellowship No.09/1236(11154)/2021-EMR-I。
文摘The Assam-Meghalaya Gneissic Complex(AMGC)of northeast India contains numerous Pan-African granitic bodies that have been attributed to post-collisional rift-related magmatism.The present study is concerned with the first appraisal of intermediate magmatism(diorite,monzonite,and monzodiorite)found in the Borjuri Pluton of Mikir Massif,which is the eastern extension of AMGC.The diorites are strongly metaluminous and exhibit enriched LREE([La/Yb]N=1.63–7.37)with respect to HREE([Gd/Yb]N=1.95–2.27).The studied rocks do not show any mineralogical or textural indication of metamorphism.Tectonic discrimination diagrams indicate that these rocks originated in a within-plate tectonic setting.The lower Mg#(33.49–38.69),low Cr(below detection limit),and Ni(27–41 ppm)contents along with elemental ratios such as Rb/Sr(0.32–0.95),La/Nb(0.49–4.21),and Nb/Ce(0.11–0.64)suggest a crustal source for the diorites.Discrimination diagrams coupled with elemental ratios suggest that these rocks originated due to partial melting of mafic components in the crust with possible contribution from mantle materials.The P–T conditions of diorite emplacement(7.4 kbar,688℃)were calculated using the amphibole-plagioclase geothermobarometer.Geochemical and geochronological data of the Pan-African felsic plutons reported from the AMGC indicate that these rocks were emplaced in a post-collisional extensional regime.The Borjuri Pluton is in close proximity with the Kathalguri Pluton,which has been reported as a product of PanAfrican magmatism.In view of the numerous extensional Pan-African felsic magmatism reported from the AMGC and based on the close vicinity of the Borjuri diorites with the Kathalguri granites,we speculate that the Borjuri diorites are products of the Pan-African post-collisional magmatism.
文摘The article presents the concept of a network of geoplutonic power plants,the total capacity of which would correspond to the general energy needs of the entire region.A scenario of a regional economy is presented,provided with electricity produced from a clean source,without pollutant emissions.Thus,a vision of solving the energy crisis resulting from the planned elimination of fossil energy sources is presented.Such an opportunity appeared after solving the technological problems of deep drilling,exceeding 10 km.The new technology involves extracting heat from HDRs(Hot Dry Rocks)and heating the fluid circulating in a pipe in a closed circuit.The temperature at a depth of 10 km is determined by the regional geothermal gradient.Temperature is in the range of 200-400°C.This is already a zone of degassing magmatic solutions and exothermic chemical reactions.In general,it can be argued that the heat flux density is a function of the distance from magmatic intrusions.
文摘黑云母是花岗岩常见的暗色矿物之一。黑云母化学成分变化是寄主岩浆固结成岩时不同的物理化学条件下所对应的结果,因此,黑云母化学成分很好地记录了寄主岩浆的属性,对黑云母开展矿物化学成分的研究可以有效地反演寄主岩岩浆演化和成岩过程的物理化学条件,指示岩石的成因类型、岩浆物质来源等信息(Wones and Eugster,1965)。
