The Khetri copper belt is a well-known metallotect in northern part of Delhi fold belt in Rajasthan. On the eastern margin of the Khetri sub basin of North Delhi basin separated by a basement high, another sub basin A...The Khetri copper belt is a well-known metallotect in northern part of Delhi fold belt in Rajasthan. On the eastern margin of the Khetri sub basin of North Delhi basin separated by a basement high, another sub basin Alwar-Ajabgarh sub basin exposes that a thick sequence of Ajabgarh group of rocks overlies a thick arenaceous sequence of Alwar group of Delhi Super Group of rocks. The Ajabgarh meta sediments here in the Neem Ka thana area are characterized by presence of Bornite dominated copper mineralization with silver association and minor presence of Pb. The mineralization has been described by various workers as strata-bound, hypogene and IOCG. But these inferences are based on part information and the inference drawn is sectorial in nature. The current study includes a holistic study based on exploration over a period of more than two decades and the data generated suggest thereof, that this syngenetic sulphide mineralization associated with the sedimentation of marl and carbonate rocks. Subsequently it has been relocated during 2<sup>nd</sup> deformation accompanied by epigenetic component of mineralization depicted in terms of vein filled coarse grained aggregates of bornite and chalcopyrite disposed across the general disposition of litho-package. The EPMA and fluid inclusion data generated from the area indicate association of typical hydrothermal environment minerals like, Perkrite, Wittchenite, Aguilarite, Molybdnite etc. The mineralizing fluids have been trapped between the temperature ranges of 130°C to 375°C with average being 250°C to 300°C. The fluid salinity also varies from near pure hot water to moderately saline fluid indicative of multi-episodic mineralization of syngenetic nature coupled with epigenetic component. The ore textures indicate 500°C temperature range;certain intergrowths of minerals like specular hematite and bornite suggest the occurrence of hypogene environment induced due to emplacement of granite/pegmatite on the eastern and southern margins of the belt. The strata bound展开更多
The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in...The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in an area;Once the rocks of an area undergo polyphase of deformation, the boudins get modified and can no longer help in determining the deformational evidences. The present study involves identification of various types of boudins their classification and morphology as per existing status of knowledge and their role in determining the type of deformation in Neem Ka Thana belt, Proterozoic rocks of North Delhi fold belt. The study of symmetric, asymmetric and modified boudins in the area enabled the author to deduce that the rocks in above belt have suffered a ployphase deformation marked with flattening type of progressive deformation during the first phase (DF1) of deformation and the second phase (DF2) with a time gap, has produced modified boudins and folded boudin structures with the largely same axis of deformation in both these deformations.展开更多
Amphiboles are frequently observed in the medium to high grade metamorphic rocks of garnet bearing amphibolites from Thana.In present work,authors have discussed the mineral chemistry and nomenclature of amphiboles.On...Amphiboles are frequently observed in the medium to high grade metamorphic rocks of garnet bearing amphibolites from Thana.In present work,authors have discussed the mineral chemistry and nomenclature of amphiboles.On the basis of mineral chemistry,the amphibole from garnet bearing amphibolite are normally varies from Hastingsite,Ferropargasite to Tschermakite variety.展开更多
文摘The Khetri copper belt is a well-known metallotect in northern part of Delhi fold belt in Rajasthan. On the eastern margin of the Khetri sub basin of North Delhi basin separated by a basement high, another sub basin Alwar-Ajabgarh sub basin exposes that a thick sequence of Ajabgarh group of rocks overlies a thick arenaceous sequence of Alwar group of Delhi Super Group of rocks. The Ajabgarh meta sediments here in the Neem Ka thana area are characterized by presence of Bornite dominated copper mineralization with silver association and minor presence of Pb. The mineralization has been described by various workers as strata-bound, hypogene and IOCG. But these inferences are based on part information and the inference drawn is sectorial in nature. The current study includes a holistic study based on exploration over a period of more than two decades and the data generated suggest thereof, that this syngenetic sulphide mineralization associated with the sedimentation of marl and carbonate rocks. Subsequently it has been relocated during 2<sup>nd</sup> deformation accompanied by epigenetic component of mineralization depicted in terms of vein filled coarse grained aggregates of bornite and chalcopyrite disposed across the general disposition of litho-package. The EPMA and fluid inclusion data generated from the area indicate association of typical hydrothermal environment minerals like, Perkrite, Wittchenite, Aguilarite, Molybdnite etc. The mineralizing fluids have been trapped between the temperature ranges of 130°C to 375°C with average being 250°C to 300°C. The fluid salinity also varies from near pure hot water to moderately saline fluid indicative of multi-episodic mineralization of syngenetic nature coupled with epigenetic component. The ore textures indicate 500°C temperature range;certain intergrowths of minerals like specular hematite and bornite suggest the occurrence of hypogene environment induced due to emplacement of granite/pegmatite on the eastern and southern margins of the belt. The strata bound
文摘The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in an area;Once the rocks of an area undergo polyphase of deformation, the boudins get modified and can no longer help in determining the deformational evidences. The present study involves identification of various types of boudins their classification and morphology as per existing status of knowledge and their role in determining the type of deformation in Neem Ka Thana belt, Proterozoic rocks of North Delhi fold belt. The study of symmetric, asymmetric and modified boudins in the area enabled the author to deduce that the rocks in above belt have suffered a ployphase deformation marked with flattening type of progressive deformation during the first phase (DF1) of deformation and the second phase (DF2) with a time gap, has produced modified boudins and folded boudin structures with the largely same axis of deformation in both these deformations.
文摘Amphiboles are frequently observed in the medium to high grade metamorphic rocks of garnet bearing amphibolites from Thana.In present work,authors have discussed the mineral chemistry and nomenclature of amphiboles.On the basis of mineral chemistry,the amphibole from garnet bearing amphibolite are normally varies from Hastingsite,Ferropargasite to Tschermakite variety.
