Occurrence of baddeleyite（ZrO_2） which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin（CIOB）.The mineral occurs either as independent isolated sub-rounded to elliptical ...Occurrence of baddeleyite（ZrO_2） which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin（CIOB）.The mineral occurs either as independent isolated sub-rounded to elliptical grains or in clusters forming fine subhedral crystals（〈3μm） within ferromanganese concretionary growth bands.The mode of occurrence,texturai features and chemistry of the mineral suggest detrital and possibly an authigenic origin for baddeleyite.For authigenic origin it is proposed that zirconium might have got released either from the terrigenous sediments or the altered seafloor rocks forming halogen complexes and subsequently it has re-precipitated in me form of baddeleyite within manganese nodules under oxic to sub-oxic conditions.展开更多
A suite of ultramafic and mafic rocks developed in the Chigu Tso area,eastern Tethyan Himalaya.Baddeleyite and zircon U-Pb ages acquired by SIMS and LA-ICP-MS from olivine pyroxenite rocks in the Chigu Tso area are 13...A suite of ultramafic and mafic rocks developed in the Chigu Tso area,eastern Tethyan Himalaya.Baddeleyite and zircon U-Pb ages acquired by SIMS and LA-ICP-MS from olivine pyroxenite rocks in the Chigu Tso area are 138.9±3.0 Ma and 139.0±1.9 Ma,respectively.These two Early Cretaceous ages are similar with the ages of the more abundant mafic rocks in the eastern Tethyan Himalaya,indicating that this suite of ultramafic and mafic rocks in the Chigu Tso area should be included in the outcrop area of the Comei Large Igneous Province(LIP).These ultramafic rocks provide significant evidence that the involvement of mantle plume/hot spot activities in the formation of the Comei LIP.Baddeleyite U-Pb dating by SIMS is one reliable and convenient method to constrain the formation time of ultramafic rocks.The dating results of baddeleyite and zircon from the olivine pyroxenite samples in this paper are consistent with each other within analytical uncertainties,suggesting that baddeleyite and zircon were both formed during the same magmatic process.The consistency of baddeleyite U-Pb ages in the Chigu Tso area with zircon U-Pb ages for a large number of Early Cretaceous mafic rocks in the eastern Tethyan Himalaya further support that zircon grains from such mafic rocks yielding Early Cretaceous ages are also magmatic in origin.展开更多
Baddeleyite is an important mineral geochronometer. It is valued in the U-Pb (ID-TIMS) geochronology more than zircon because of its magmatic origin, while zircon can be metamorphic, hydrothermal or occur as xenocryst...Baddeleyite is an important mineral geochronometer. It is valued in the U-Pb (ID-TIMS) geochronology more than zircon because of its magmatic origin, while zircon can be metamorphic, hydrothermal or occur as xenocrysts. Detailed mineralogical (BSE, KL, etc.) research of baddeleyite started in the Fennoscandian Shield in the 1990s. The mineral was first extracted from the Paleozoic Kovdor deposit, the second-biggest baddeleyite deposit in the world after Phalaborwa (2.1 Ga), South Africa. The mineral was successfully introduced into the U-Pb systematics. This study provides new U-Pb and LA-ICP-MS data on Archean Ti-Mgt and BIF deposits, Paleoproterozoic layered PGE intrusions with Pt-Pd and Cu-Ni reefs and Paleozoic complex deposits (baddeleyite, apatite, foscorite ores, etc.) in the NE Fennoscandian Shield. Data on concentrations of REE in baddeleyite and temperature of the U-Pb systematics closure are also provided. It is shown that baddeleyite plays an important role in the geological history of the Earth, in particular, in the break-up of supercontinents.展开更多
Mafic dykes preserved important information on mantle melting regimes in the early Earth history.Despite the fact that a large volume of geochronological data for mafic dykes was recently received,several important is...Mafic dykes preserved important information on mantle melting regimes in the early Earth history.Despite the fact that a large volume of geochronological data for mafic dykes was recently received,several important issues展开更多
The Dharwar Craton in Peninsular India was intruded by a series of mafic dykes during the Paleoproterozoic and these mafic magmatic events have important implications on continental rifting and LIPs.Here we report ten...The Dharwar Craton in Peninsular India was intruded by a series of mafic dykes during the Paleoproterozoic and these mafic magmatic events have important implications on continental rifting and LIPs.Here we report ten precise Pb-Pb TE-TIMS age determinations on baddeleyite grains separated from seven mafic dykes and three sills,intruding into Archean basement rocks and Proterozoic sedimentary formations of the Eastern Dharwar Craton respectively.The crystallization age of the baddeleyite shows 2366.3±1.1 Ma,and 2369.2±0.8 Ma for the NE-SW trending dykes,2368.1±0.6 Ma,2366.4±0.8 Ma,2207.2±0.7 Ma and 1887.3±1.0 Ma for the ENE-WNW to E-W striking dykes,1880.6±1.0 Ma,1864.3±0.6 Ma and 1863.6±0.9 Ma for Cuddapah sills,and 1861.8±1.4 Ma for the N-S trending dyke.Our results in conjunction with those from previous studies identify eight distinct stages of widespread Paleoproterozoic magmatism in the Dharwar craton.The mantle plume centres of the four radiating dyke swarms with ages of^2367 Ma,~2210 Ma,~2082 Ma,and^1886 Ma were traced to establish their proximity to the EDC kimberlite province.Though the^2367 Ma and^1886 Ma plume centres are inferred to be located to the west and east of the present day Dharwar craton respectively away from the kimberlite province,location of plume heads of the other two swarms with ages of^2207 Ma and^2082 Ma are in close proximity.In spite of the ubiquitous occurrence of dyke intrusions of all the seven generations in the kimberlite province,only few of these kimberlites are diamondiferous.Kimberlite occurrences elsewhere in the vicinity of older Large Igneous Provinces(LIPs)like the Mackenzie,Karoo,Parana-Etendeka and Yakutsk-Vilui are also non-diamondiferous.This has been attributed to the destruction of the lithospheric mantle keel(that hosts the diamonds)by the respective mantle plumes.The diamondiferous nature of the EDC kimberlites therefore suggests that plume activity does not always result in the destruction of the mantle keel.展开更多
The Early Paleoproterozoic Monchegorsk Complex is exposed over an area of 550 km;and comprises two layered mafite–ultramafite intrusions:the Monchepluton of ultramafic and mafic rocks and the predominantly gabbroid
A precise U-Pb baddeleyite age of 1999±2 Ma has been obtained for the NNW trending Lac Shpogan dyke swarm of the James Bay area of the eastern Superior craton.Previously the age of the swarm was only
基金the"CSIR-Young Scientist Award Project"(OLP-0103 of NML) sanctioned to B.Nayak by CSIR,New Delhi
文摘Occurrence of baddeleyite（ZrO_2） which is a rare mineral has been recorded in ferromanganese nodules of Central Indian Ocean Basin（CIOB）.The mineral occurs either as independent isolated sub-rounded to elliptical grains or in clusters forming fine subhedral crystals（〈3μm） within ferromanganese concretionary growth bands.The mode of occurrence,texturai features and chemistry of the mineral suggest detrital and possibly an authigenic origin for baddeleyite.For authigenic origin it is proposed that zirconium might have got released either from the terrigenous sediments or the altered seafloor rocks forming halogen complexes and subsequently it has re-precipitated in me form of baddeleyite within manganese nodules under oxic to sub-oxic conditions.
基金The authors thank and appreciate Qiu-li Li and Ke-jun Hou for their help in guiding the dating work.This study was supported by National Science Foundation of China(41425010,41430212)China Geological Survey Project(DD20190057)+1 种基金National Key Research and Development Project of China(2016YFC0600304)Basic scientific research fund in Institute of Geology,CAGS(J1901-1,J1901-10).
文摘A suite of ultramafic and mafic rocks developed in the Chigu Tso area,eastern Tethyan Himalaya.Baddeleyite and zircon U-Pb ages acquired by SIMS and LA-ICP-MS from olivine pyroxenite rocks in the Chigu Tso area are 138.9±3.0 Ma and 139.0±1.9 Ma,respectively.These two Early Cretaceous ages are similar with the ages of the more abundant mafic rocks in the eastern Tethyan Himalaya,indicating that this suite of ultramafic and mafic rocks in the Chigu Tso area should be included in the outcrop area of the Comei Large Igneous Province(LIP).These ultramafic rocks provide significant evidence that the involvement of mantle plume/hot spot activities in the formation of the Comei LIP.Baddeleyite U-Pb dating by SIMS is one reliable and convenient method to constrain the formation time of ultramafic rocks.The dating results of baddeleyite and zircon from the olivine pyroxenite samples in this paper are consistent with each other within analytical uncertainties,suggesting that baddeleyite and zircon were both formed during the same magmatic process.The consistency of baddeleyite U-Pb ages in the Chigu Tso area with zircon U-Pb ages for a large number of Early Cretaceous mafic rocks in the eastern Tethyan Himalaya further support that zircon grains from such mafic rocks yielding Early Cretaceous ages are also magmatic in origin.
文摘Baddeleyite is an important mineral geochronometer. It is valued in the U-Pb (ID-TIMS) geochronology more than zircon because of its magmatic origin, while zircon can be metamorphic, hydrothermal or occur as xenocrysts. Detailed mineralogical (BSE, KL, etc.) research of baddeleyite started in the Fennoscandian Shield in the 1990s. The mineral was first extracted from the Paleozoic Kovdor deposit, the second-biggest baddeleyite deposit in the world after Phalaborwa (2.1 Ga), South Africa. The mineral was successfully introduced into the U-Pb systematics. This study provides new U-Pb and LA-ICP-MS data on Archean Ti-Mgt and BIF deposits, Paleoproterozoic layered PGE intrusions with Pt-Pd and Cu-Ni reefs and Paleozoic complex deposits (baddeleyite, apatite, foscorite ores, etc.) in the NE Fennoscandian Shield. Data on concentrations of REE in baddeleyite and temperature of the U-Pb systematics closure are also provided. It is shown that baddeleyite plays an important role in the geological history of the Earth, in particular, in the break-up of supercontinents.
基金supported by Russian Science Foundation,grant№16-17-10260
文摘Mafic dykes preserved important information on mantle melting regimes in the early Earth history.Despite the fact that a large volume of geochronological data for mafic dykes was recently received,several important issues
文摘The Dharwar Craton in Peninsular India was intruded by a series of mafic dykes during the Paleoproterozoic and these mafic magmatic events have important implications on continental rifting and LIPs.Here we report ten precise Pb-Pb TE-TIMS age determinations on baddeleyite grains separated from seven mafic dykes and three sills,intruding into Archean basement rocks and Proterozoic sedimentary formations of the Eastern Dharwar Craton respectively.The crystallization age of the baddeleyite shows 2366.3±1.1 Ma,and 2369.2±0.8 Ma for the NE-SW trending dykes,2368.1±0.6 Ma,2366.4±0.8 Ma,2207.2±0.7 Ma and 1887.3±1.0 Ma for the ENE-WNW to E-W striking dykes,1880.6±1.0 Ma,1864.3±0.6 Ma and 1863.6±0.9 Ma for Cuddapah sills,and 1861.8±1.4 Ma for the N-S trending dyke.Our results in conjunction with those from previous studies identify eight distinct stages of widespread Paleoproterozoic magmatism in the Dharwar craton.The mantle plume centres of the four radiating dyke swarms with ages of^2367 Ma,~2210 Ma,~2082 Ma,and^1886 Ma were traced to establish their proximity to the EDC kimberlite province.Though the^2367 Ma and^1886 Ma plume centres are inferred to be located to the west and east of the present day Dharwar craton respectively away from the kimberlite province,location of plume heads of the other two swarms with ages of^2207 Ma and^2082 Ma are in close proximity.In spite of the ubiquitous occurrence of dyke intrusions of all the seven generations in the kimberlite province,only few of these kimberlites are diamondiferous.Kimberlite occurrences elsewhere in the vicinity of older Large Igneous Provinces(LIPs)like the Mackenzie,Karoo,Parana-Etendeka and Yakutsk-Vilui are also non-diamondiferous.This has been attributed to the destruction of the lithospheric mantle keel(that hosts the diamonds)by the respective mantle plumes.The diamondiferous nature of the EDC kimberlites therefore suggests that plume activity does not always result in the destruction of the mantle keel.
文摘The Early Paleoproterozoic Monchegorsk Complex is exposed over an area of 550 km;and comprises two layered mafite–ultramafite intrusions:the Monchepluton of ultramafic and mafic rocks and the predominantly gabbroid
文摘A precise U-Pb baddeleyite age of 1999±2 Ma has been obtained for the NNW trending Lac Shpogan dyke swarm of the James Bay area of the eastern Superior craton.Previously the age of the swarm was only
