Detrital and authigenic(?) baddeleyite(ZrO_2) in ferromanganese nodules of Central Indian Ocean Basin

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.

Baddeleyite and zircon U-Pb ages of the ultramafic rocks in Chigu Tso area,Southeastern Tibet and their constraints on the timing of Comei Large Igneous Province

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.

Mafic Dyke Records of Paleoproterozoic Mantle Plume Activity in the Karelian Craton: U-Pb Baddeleyite/Zircon Geochronology and Sr-Nd Isotopic Data

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

Pb–Pb baddeleyite ages of mafic dyke swarms from the Dharwar Craton:Implications for Paleoproterozoic LIPs and diamond potential of mantle keel

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.

U-Pb SHRIMP-II Baddeleyite and Zircon Dating of the Early Proterozoic Monchegorsk Layered Mafite-Ultramafite Complex(Kola Peninsula): Evidence of Synchronous Magmatism

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

Minto Large Igneous Province: A 2.00 Ga Mafic Magmatic Event in the Eastern Superior Craton Based on U-Pb Baddeleyite Geochronology and Paleomagnetism

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

Baddeleyite from Large Complex Deposits: Significance for Archean-Paleozoic Plume Processes in the Arctic Region (NE Fennoscandian Shield) Based on U-Pb (ID-TIMS) and LA-ICP-MS Data

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.

氢化锆表面氢渗透阻挡层形貌和组织分析

用氧化预处理和电镀法在氢化锆表面生成Cr-C镀层,经过400℃、10h预加热得到氢渗透阻挡层并对试样进行加热至700℃、保温10h的氢渗透试验。用XRD对氢渗透阻挡层的组成物进行了分析,用SEM对氢渗透试验后的阻挡层表面和截面进行观察和微区成分分析。分析结果表明,该阻挡层中存在Cr2O3、金属Cr、O和C,阻挡层与基体之间存在一个由baddeleyite结构的ZrO2组成的致密的过渡层;阻挡层基本致密。

Crystallization and impact history of a meteoritic sample of early lunar crust(NWA 3163)refined by atom probe geochronology

Granulitic lunar meteorites offer rare insights into the timing and nature of igneous,metamorphic and impact processes in the lunar crust.Accurately dating the different events recorded by these materials is very challenging,however,due to low trace element abundances (e.g.Sm,Nd,Lu,Hf),rare micrometerscale U-Th-bearing accessory minerals,and disturbed Ar-Ar systematics following a multi-stage history of shock and thermal metamorphism.Here we report on micro-baddeleyite grains in granulitic mafic breccia NWA 3163 for the first time and show that targeted microstructural analysis (electron backscatter diffraction) and nanoscale geochronology (atom probe tomography) can overcome these barriers to lunar chronology.A twinned (-90°/<401>) baddeleyite domain yields a 232Th/208Pb age of 4328 ± 309 Ma,which overlaps with a robust secondary ion mass spectrometry (SIMS) 207Pb/206Pb age of 4308± 18.6 Ma and is interpreted here as the crystallization age for the igneous protolith of NWA 3163.A second microstructural domain,< 2 mm in width,contains patchy overprinting baddeleyite and yields a Th-Pb age of 2175± 143 Ma,interpreted as dating the last substantial impact event to affect the sample.This finding demonstrates the potential of combining microstructural characterization with nanoscale geochronology when resolving complex P-T-t histories in planetary materials,here yielding the oldest measured crystallization age for components of lunar granulite NWA 3163 and placing further constraints on the formation and evolution of lunar crust.

Controlled Reduction of Iron Content in Zirconiun Ore:A Case Study in Polyphase Mineralization,Pocs de Caldas Alkaline Plateau

In PCAC(Po?os de Caldas Alkaline Complex),in southeastern Brazil,it is observed a polyphase mineralization related to Zr-,U-,Th-,Mo-,and REE-enrichment due to hydromethermal processes which affected alkaline primary rock.Primary Zr-minerals were leached and concentrated as“caldasite”,a rock composed mainly by zircon and baddeleyite in different proportions.Several techniques of mineralogical characterization were applied and results indicated zircon,baddeleyite,magnetite and iron-oxyhydroxides,mainly.Magnetic separation by WHIMS(Wet High-Intensity Magnetic Separation)was performed in order to indicate the efficiency for Fe-concentration removal for potential application in refractory industry.

SIMS Pb/Pb dating of Zr-rich minerals in lunar meteorites Miller Range 05035 and LaPaz Icefield 02224:Implications for the petrogenesis of mare basalt

Miller Range (MIL) 05035 and LaPaz Icefield (LAP) 02224 are unbrecciated lunar basalt meteorites. In this report, we studied their petrography and mineralogy and made in situ uranogenic Pb/Pb dating of Zr-rich minerals. Petrography and mineralogy of these two lunar meteorites are consistent with previous investigations. The zirconolite Pb/Pb age of MIL 05035 is 3851±8 Ma (2σ), in excellent agreement with previous reports. This age suggests that MIL 05035 could be paired with Asuka 881757, a low-Ti mare basalt meteorite. The magmatic event related to MIL 05035 was probably due to the late heavy impact bom- bardment on the moon around 3.9 Ga. One baddeleyite grain in LAP 02224 shows a large variation of Pb/Pb age, from 3109±29 to 3547±21 Ma (2σ), much older than the whole-rock age of the same meteorite (~3.02±0.03 Ga). The other baddeleyite grain in LAP 02224 has an age of 3005±17 Ma (2σ). The result indicates that the minimum crystallization age of LAP 02224 is ~3.55 Ga and the younger ages could reflect late thermal disturbance on U-Pb system.

Phase equilibrium modeling of zircon stability in mantle peridotite:Implication for crust-mantle interaction

Zircon is a common accessory mineral in various rocks,especially in the crustal ones.It is the best mineral for U-Pb dating.Meanwhile,trace elements and isotopes of the mineral can also provide much information concerning the formation and evolution of rocks.There are a growing number of reports of zircon existing in mantle peridotite.However,it is generally considered that zircon is unlikely crystallized in ultrabasic rocks due to SiO_(2)-unsaturation.In this paper,the SiO_(2) activity and zircon/baddeleyite transition curve at different conditions were calculated through thermodynamic phase equilibrium modeling,to reveal the main factors affecting the SiO_(2) activity and the stability of zircon/baddeleyite in ultrabasic and basic rocks,especially in mantle peridotite.These results provide a thermodynamic basis for interpreting the genesis and significance of zircon in mantle rocks.That is,the SiO_(2) activity is mainly controlled by stable mineral assemblages and temperature-pressure conditions.The orthopyroxene+olivine assemblage in peridotite as an effective buffer restricts the SiO_(2) activity in a relatively high range with a small variation.The upper temperature limit of zircon can reach more than 1500℃ with this mineral assemblage.During the low-temperature serpentinization of peridotite,the replacement of olivine and pyroxene by serpentine can result in a significant decrease of SiO_(2) activity,and baddeleyite can be stabilized at<530℃ and<2.7 GPa.When peridotite is strongly metasomatized by the SiO_(2)-bearing fluid,the addition of SiO_(2) can increase its activity and make zircon stable at low temperatures.The SiO_(2) activity in ultrabasic-basic rocks is not only positively correlated with the SiO_(2) content but also negatively correlated with the Ca and Na contents of rocks.This is because Ca and Na preferentially combine with Si and Al to form Si-rich minerals,such as clinopyroxene and feldspar.This process will consume excessive SiO_(2),decreasing the SiO_(2) activity.This may be the reason why zircon can be found in ultrabasic rocks,while baddeleyite can exist in some basic and alkaline rocks.The thermodynamic modeling can also reasonably explain the mutual transformation between zircon and baddeleyite in ultrabasic-basic rocks.Our results indicate that zircon can exist stably in mantle peridotite in a wide range of temperature-pressure conditions and its formation is related to melt/fluid metasomatism.That is,the presence of zircon in mantle peridotite is an important information carrier of crust-mantle interaction for deep material cycling.