Hf Composition Research Articles

Exploring the short and long-range order in connection with fluorine content in mixed anions copper hydroxyfluorides

Hydroxyl-rich (Cu-LF) and Fluorine-rich (Cu–HF) copper hydroxyfluorides Cu(OH)2-xFx (x = 0.4–0.5 and x = 0.9–1.5) were prepared by precipitation route followed by hydrothermal process where the starting pH and the HF molar content play a key role. Based on powder XRD and PDF analysis, long range and short order were evidenced with various Cu–O/F bondlengths illustrating the Jahn-teller distortion as well as the Cu–Cu intra-sheet and interslab interactions. Tuning the fluorine content allows chemical bonding modulation by antagonist effect, resulting for instance in the weakening of H bonding in the hydroxyl-rich compound. When the fluorine content increases, the average structures evolve from a disordered network with a random distribution of anions in the vicinity of Cu2+ in Cu-LF to a well ordered mixed anions phase where Cu(OH)3F3/Cu(OH)2F4/Cu(OH)5F distorted octahedra are close to C2h point group symmetry. Raman spectroscopy confirm the average structural features with the point group symmetry. One should outline in Cu–HF composition, stronger CuF3(OH)3 octahedron stiffness associated to a stretching O–H mode at lower frequency, synonymous of O–H bond weakening and consequently stronger hydrogen bonding in agreement with PDF analysis. UV–visible–NIR spectra show in Cu–HF hydroxyfluoride, an increase of the optical band gap of 0.6 eV and a decrease of Cu2+(3 d9) crystal field splitting of 0.1 eV in agreement with the larger fluorine content. However, the dxz-dyz orbital splitting increases of 0.2 eV in Cu–HF in good agreement with the C2h point group symmetry and the related distortion. Finally, whereas the hydroxyl-rich Cu-LF phase decomposes into CuO at T > 300 °C, the Fluorine rich Cu–HF compound lead at T > 320 °C to the formation of CuF2, Cu2O in addition to CuO. This unusual reduction process Cu2+ → Cu+ at low temperature is associated to the strengthening of Cu–O/F and Cu–Cu bonding in the basal plane of Cu(OH)3F3 distorted octahedron.

Ultrahigh in-plane uniaxial magnetic anisotropy of amorphous FeCoHf composition gradient films

Amorphous FeCoHf films with a Hf composition gradient were prepared at room temperature. The composition gradient sputtering technique was used to control the composition gradient of the doped element Hf by changing the deposition power of Hf. Interestingly, in the as-deposited FeCoHf films, an in-plane uniaxial magnetic anisotropy field of up to 640 Oe was achieved, and the resonance frequency was 6.5 GHz. The large anisotropy field can be attributed to the high sensitivity of the amorphous FeCoHf films to the composition gradient. The ultrahigh anisotropy exhibited by FeCoHf films at room temperature holds significant technological potential for various applications.

Grenvillian evolution of the Qaidam block and its position in Rodinia constrained by U–Pb–Hf composition of detrital zircons from the Altyn Tagh, Northern Tibet

The U–Pb ages and Hf isotopic composition of detrital zircons provide important constraints on basin evolution and paleogeography. The Qaidam block, a continental fragment along the northeastern margin of the Tibetan Plateau, has been suggested to have been either in an internal or a peripheral position in Rodinia. We present a systematic study of late Mesoproterozoic to Ediacaran sedimentary sequences from the Altyn Tagh belt, a part of the Qaidam block displaced by the Altyn Tagh fault, in an effort to establish its position within Rodinia. The (meta-)sedimentary rocks of the Altyn Complex of South Altyn can be correlated with the Taxidaban Group, the part of the basement(meta-)sedimentarysequence of Central Altyn, on the basis of lithological and geochronological similarities. Both of these were deposited in the late Mesoproterozoic to early Neoproterozoic. The early Neoproterozoic Suoerkuli Group of Central Altyn and its coeval magmatism formed in an extensional setting. This extensional episode facilitated thinning of the lithosphere during the late Tonian–Ediacaran when the sedimentary protoliths of the Hongliuquan Complex were deposited. Detrital zircon grains from late Mesoproterozoic to Ediacaran sedimentary sequences in the Altyn Tagh orogenic belt show a wide distribution of Meso- and Paleoproterozoic ages between 1800 and 1000 Ma, which match well with contemporaneous supracrustal sequences in northeastern Laurentia. In combination with the similarity in late Mesoproterozoic to Ediacaran tectono-thermal events, we propose the Qaidam block was located along the northeast Laurentian margin during the late Meso- to Neoproterozoic assembly of Rodinia.

Detrital zircon LA-ICPMS U-Pb and Lu-Hf signature from the Mesoarchean Keonjhar Quartzite: Implications for the nature of Archean continental crust and geodynamics

• The Keonjhar Quartzite represents records of Mesoarchean sedimentation. • The detrital zircon LAICPMS Lu-Hf reveals superchondritic Hf isotopic compositions. • Superchondritic Hf composition suggests juvenile crustal components at source. • A stagnant lid to low angle subduction geodynamic regime for origin of granitoids. The ∼715 m thick matured siliciclastics of the Keonjhar Quartzite, North of the homonymous town, Singhbhum Craton, eastern India, represents one of the best-preserved examples of sedimentation during Mesoarchean time. The LA-ICPMS U-Pb ages with peaks at 3.2 Ga, 3.1 Ga, 3.0 Ga and 2.87 Ga of the detrital zircon grains from the upper part of the Keonjhar Quartzite reveal youngest age population of ∼2.87 Ga. The Hf isotopic compositions have mean initial 176 Hf/ 177 Hf ratio of 0.280897 and low Lu/Hf ratio of 0.01. Most of the grains of the zircon population show positive εHf (+8.75 to +0.26) values with only two negative values of -0.05 and -3.27. The superchondritic Hf isotopic compositions suggest depleted mantle source, juvenile crustal components and possible role of juvenile crust formation presumably in a stagnant lid to low angle subduction geodynamic regime for the origin of granitoids that sourced the detrital zircon grains.

U-Pb zircon LA-ICP-MS and Hf composition in granitogneiss of Chu Lai body and its implication of the Kontum massif, central Vietnam

The Chu Lai granitogneiss is widespread throught the Northern Kontum massif. The Chu Lai body is located in the W-SW of the Nui Thanh Townlet (Nui Thanh Dists., Quang Nam Prov.). On an areas of ~ 300 km2. The Chu Lai intrusion mainly consists two mica gneiss, it is light grey and have porphyritic textures. Its major minerals include plagioclase (25÷40%), K-feldpar (20÷40%), quartz (25÷35%), biotite (5÷13%) and mustcovite (0÷6%). Accessory minerals are apatite, zircon, orthit. Garnet and tourmaline are occiasionally found. Zircons separated from a granitogneiss sample colleted in Chu Lai body are generally euhedral to subhedral, dark gray and prissmatic in shape with 100÷300 µm, with length/witdth ratios from 1:1÷1:3. There are many Neoproterozoic - Cambrian ages among the zircon cores in the Chu Lai samples, and these are regarded as inherited zircons. The LA-ICP-MS zircon age is 431 Ma, corresponding to the Silurian. The Chu Lai granitogneiss strongly negative zircon εHf (-4.2÷-11.4) and complex inherited zircon components, characteristics of typical S-type granite. Hf model ages TDM2 1.5÷1.9 Ga, suggests that the Chu Lai granitogneiss was derived from partial melting of old crustal basement rocks, probaly Paleoproterozoic in age.

Combinatorial search for Ti–Ni–Hf high formable shape memory alloys

In this study, we searched for Ti–Ni–Hf high formable shape memory alloys (HFSMAs) using combinatorial methods. By adding Hf to Ti–Ni SMAs, the potential is that Ti–Ni SMAs become metallic glasses. For efficient material search, the glass transition temperature was evaluated through combinatorial measurement of electrical resistance during crystallization. From the results, we searched for Ti–Ni–Hf HFSMAs, which undergo glass transition in the amorphous state. Ni-rich Ti–Ni–Hf thin-film amorphous alloys with more than 10 at% Hf content became thin film metallic glasses, whereas Ni-poor samples did not. Further, we evaluated the effect of annealing temperature on the martensitic transformation temperature of Ti–Ni–Hf SMAs using combinatorial methods. From the results, we measured the reverse transformation start temperature A s at 368–404 K, and it varied with the annealing temperature and Hf composition.

Tracing southern Gondwanan sedimentary paths: A case study of northern Namibian late Palaeozoic sedimentary rocks

AbstractThe northern Namibian Karoo‐aged successions are part of a Gondwana‐wide sedimentary system emerging at the Carboniferous–Permian boundary and existing for more than 50 Ma. The Karoo Supergroup sedimentary successions are of importance in understanding the evolution of the Karoo rift system. This study presents new whole‐rock geochemical data combined with detrital zircon morphology as well as U−Pb ages and Lu−Hf composition of late Palaeozoic siliciclastic rocks of the Namibian Huab Basin and Kunene area (south‐west Africa). Inferred by youngest detrital zircon U−Pb ages the Verbrande Berg Formation (lower Ecca Group) yields a Sakmarian to Asselian maximum depositional age, whereas the overlying Tsarabis Formation yields an Artinskian maximum depositional age. These ages coincide with the end of the Dwyka ice age and an overall warming and a contemporaneous evolution of the Karoo I rift system across southern Gondwana. The zircon age distribution of the investigated samples yields clusters ranging between ca 500 to 650 Ma (Cambrian–late Neoproterozoic), ca 950 to 1200 Ma (early Neoproterozoic–Mesoproterozoic) and ca 1800 to 1900 Ma (Palaeoproterozoic). Their rounded shapes characterize the zircon grains of the Kunene area and the lower Huab Basin section, whereas upper Huab Basin strata yield mostly unrounded grains. The rounded nature of zircon grains with a diverse U−Pb age spectrum putatively points towards sediment homogenization and multiple recycling stages during the deposition of the sediments and large catchment areas of the depositing rivers. As suggested by zircon grains with a low roundness value and a single Palaeoproterozoic age cluster, the upper Huab Basin successions were probably deposited under drier climatic conditions, small catchment areas and limited sedimentary homogenization. Therefore, the southern Gondwana sedimentary transport and homogenization system may change over time and is dependent on the climate prevailing during deposition. This study shows that the laws of detrital zircon are very complex and are yet to be explored.

Compositional Engineering of Hf‐Doped InZnSnO Films for High‐Performance and Stability Amorphous Oxide Semiconductor Thin Film Transistors

AbstractThe Hf‐doped indium zinc tin oxide (Hf:InZnSnO) channel for high performance and stable transparent thin film transistors (TFTs) is developed by using a simultaneous cosputtering of InZnSnO and HfO2 targets. The effects of In and Hf composition in Hf:InZnSnO channel on the performance and stability under bias stress for the Hf:InZnSnO channel‐based TFTs are investigated. Herein, the In cations enhance the electrical properties, while the Hf cations reduce the oxygen vacancies in the Hf:InZnSnO channel layer. Adjusting the atomic ratio of In of the InZnSnO target improves the performance of the Hf:InZnSnO‐based TFTs, while introducing an adequate amount of HfO2 improves the bias stabilities and hysteresis characteristics of the Hf:InZnSnO‐based TFTs. The transparent TFT with optimized Hf:InZnSnO channel, with a stoichiometry of Hf0.27In25.96Zn6.99Sn6.16O60.62, that is cosputtered at RF power of 100 W applied to InZnSnO target (In:Zn:Sn = 4:1:1 at%), and RF power of 50 W applied to HfO2 target exhibits a field effect mobility of 11.84 cm2 V−1 s−1 and low shift of threshold voltage of less than 2.5 V under bias stress for 3000 s. The high performance and stability of the Hf:InZnSnO channel‐based TFTs demonstrate the feasibility of transparent TFTs‐related next‐generation display applications.

Mechanical and Thermal Behavior of Cu84−xAl13Ni3Hfx Shape Memory Alloys

The physical characteristics of a shape memory alloy can be controlled by different production techniques and the rate of constituents’ contribution. In this study, CuAlNiHf shape memory alloys, with three different amounts of Hf, were produced by the induction melting method. Many measurements such as differential scanning calorimetry (DSC), scanning electron microscope, energy dispersive X-ray, and the stress–strain test were carried out. The DSC measurement showed that the austenite transformation temperatures were decreased by doping more amount of hafnium into the alloy. All specimens showed a wide temperature hysteresis, which decreased by increasing Hf content. Also, the elastic modulus was raised by increasing the Hf amount. Although $${\gamma }_{1}^{{\prime}}$$ and $${\beta }_{1}^{{\prime}}$$ are the dominant phases in the CuAlNiHf with low Hf composition, substituting Cu with Hf enhanced the amount $${\beta }_{1}^{{\prime}}$$ -phase compared to $${\gamma }_{1}^{{\prime}}$$ -phase.

Influence of codoping with Hf and La on grain‐boundary transport in alumina

AbstractThe role of reactive elements (RE) is an important topic in understanding the oxidation behavior of high‐temperature alloys. In this work, the influence of codoping alumina with two different RE elements (500 ppm Hf + 500 ppm La) was studied. The kinetics of oxygen grain‐boundary (GB) transport were studied at 1400°C using metallic nickel particles as markers. The results were compared with data obtained on the corresponding singly doped compositions; alumina‐500 ppm La, and alumina‐500 ppm Hf. The results showed that singly doping with La did not have any benefit compared to undoped alumina, whereas singly doping with Hf resulted in a slowing of transport by a factor of ~7. The behavior of the codoped sample was very similar to that of the singly doped Hf composition. For all the studied compositions, atomic scale characterization using high‐angle annular dark‐field scanning transmission electron microscopy and atom probe tomography (APT) revealed strong segregation of the dopant ions to the alumina grain boundaries. In the codoped sample, APT revealed evidence of oxygen excess and aluminum depletion at the GB core.

Crustal Evolution in the New England Orogen, Australia: Repeated Igneous Activity and Scale of Magmatism Govern the Composition and Isotopic Character of the Continental Crust

AbstractThe generation of continental crust, its bulk composition and temporal evolution provide important records of plate tectonics and associated magma-generating processes. However, the long-term integrated effects of repeated magmatic events on crustal growth, composition and differentiation and, therefore, on crustal evolution are rarely considered. Here, we examine long-term (∼350 Myr) temporal compositional trends of granitic magmatism within a limited (∼200 km × 100 km) area in the Northern New England Orogen of Queensland, Australia to avoid lateral crustal variations in order to understand how temporal–compositional variations of silicic igneous rocks record crustal evolution. Long-term temporal compositional variations are tracked using whole-rock chemistry, zircon chronochemistry and zircon Hf isotopic compositions. We particularly focus on whole-rock U, Th and K abundances and calculated heat-production values as proxies for crustal evolution, and tracking crustal sources involved in granitic magmatism. We identified two major compositional groupings within the study area that were repeatedly produced over time: compositional Group 1 comprises voluminous I-type igneous rocks emplaced during the Permo-Carboniferous and Early Cretaceous; Group 2 represents mainly lower volume A-type igneous rocks of Triassic, Middle Cretaceous and Tertiary age. Importantly, these compositional groupings alternate over the 350 Myr history of granitic magmatism within the study area. Heat-production values over time exhibit a zigzag pattern and mirror zircon Hf isotopic signatures where rocks with elevated heat-production values exhibit unradiogenic (crustal) Hf isotopic compositions. We identify the composition of crustal sources, level of the crust undergoing partial melting, scale of magmatism and source crustal volume as important factors in understanding the compositional diversity of silicic igneous rocks. We interpret the two chemical groupings to reflect the following magma-generating conditions: Group 1 igneous rocks record large-scale magmatic systems triggered by extensive crustal melting of multiple lower to middle crustal sources, which produce more compositionally and isotopically uniform magma compositions that approach bulk crustal compositions. In contrast, Group 2 igneous rocks reflect smaller-scale magmatic systems generated from smaller-scale partial melting events of the middle to upper crust that produced A-type magmas. Over the long term, the successive large-scale magmatic events (recorded by Group 1 igneous rocks) through their concomitant basaltic underplating make the Hf composition of the lower crust more radiogenic, and tend to homogenize the isotopic composition of the continental crust. We consider three important coupled controls: (1) promotion of extensive crustal melting by large-scale magmatic systems, potentially blending multiple crustal sources that can also include a significant juvenile source contribution; (2) melt depletion, whereby older, and potentially more unradiogenic crustal materials become more refractory; (3) ‘crustal jacking’, where mantle-derived magmas are added as underplate to the crust (i.e. basification) and can shift older crustal materials to more shallow levels (potentially in concert with erosion and exhumation) and away from zones of crustal melting. Our findings highlight the importance of integrating the geological and intrusive history with whole-rock geochemical data and isotopic information, and have direct implications for continental regions that exhibit protracted igneous histories and where isotopic compositions may trend towards more juvenile compositions such as circum-Pacific or retreating accretionary orogens.

Paleoproterozoic (ca. 1.87–1.69 Ga) arc-related tectonothermal events on northcentral Yeongnam Massif, South Korea and its tectonic implications: Insights from metamorphism, geochemistry and geochronology

The Paleoproterozoic basement of the Korean Peninsula consists of three massifs, the Nangrim, Gyeonggi and Yeongnam Massifs, from north to south. In the Muju area of the northcentral Yeongnam Massif, amphibolites intruded the Paleoproterozoic metasedimentary rocks and orthogneisses. The amphibolites can be divided into Type-I and Type-II amphibolites. The whole-rock geochemical data and zircon Lu–Hf composition of the amphibolites suggest that the Type-I and Type-II amphibolites formed in an island and continental arc tectonic setting, respectively, and both amphibolites were derived from enriched mantle sources. Zircon U–Pb dating reveals that the Type-I and Type-II amphibolites were emplaced at ca. 1.87 Ga and 1.69 Ga, respectively. The surrounding metasedimentary rock (migmatite) underwent upper amphibolite facies (720–730 °C and 7.3–7.4 kbar) metamorphism and then underwent amphibolite facies retrograde metamorphism (520–622 °C and 1.7–3.5 kbar). The zircon U–Pb dating reveals that the peak metamorphism occurred at ca. 1.87–1.86 Ga. The geothermal gradient (approximately 32 °C/km) during peak metamorphism correlates with that of the arc area, indicating that metamorphism occurred in an arc tectonic setting. These data suggest that the northcentral Yeongnam Massif underwent arc-related magmatic and metamorphic events during ca. 1.87–1.69 Ga. This finding indicates that the northcentral Yeongnam Massif does not correlate well with the Nangrim and northern Gyeonggi Massifs, which are correlated with the eastern North China Craton, because the Nangrim and Gyeonggi Massifs underwent postcollisional igneous activity during ca. 1.88–1.84 Ga.

U-Pb zircon and Hf composition of granite Song Ma block

The granite of the Song Ma block mainly consists of two types of granite: biotite granite and hornblende-biotite granite. Biotite granites have the percent of plagioclase (35– 45%), K-feldspar (25–35%), quartz (~20%) and biotite (~10%). Biotite-hornblende granite with the content of plagioclase (40–50%), Kfeldspar (10–15%), hornblende (5–10%) and biotite (5%). Zircon crystals were selected from the granite of Song Ma block are V0741, V0856 and V1006 samples with the LA-ICPMS U-Pb analyses gave concordant ages concentrated at 257±4Ma, 262±3Ma and 241±6Ma (weighted mean). Those ages are older than the results of the previous research. The mineral assemblages and geochemical characteristics show the typical of I-type granites. The results of Hf isotope composition analysis give the value of εHf(t) from +7.3 to +13.9, which is proven the sources of the granite Song Ma block similar to the granite of Phan Si Pan zone, NW Viet Nam during the period from late Permian to early Triassic.

Radiation-induced transformation of Hafnium composition

Abstract The safety and efficiency of nuclear reactors largely depend on the monitoring and control of nuclear radiation. Due to the unique nuclear-physical characteristics, Hf is one of the most promising materials for the manufacturing of the control rods and the emitters of neutron detectors. It is proposed to use the Compton neutron detector with the emitter made of Hf in the In-core Instrumentation System (ICIS) for monitoring the neutron field. The main advantages of such a detector in comparison the conventional β-emission sensors are the possibility of reaching of a higher cumulative radiation dose and the absence of signal delays. The response time of the detection is extremely important when a nuclear reactor is operating near its critical operational parameters. Taking Hf as an example, the general principles for calculating the chains of materials transformation under neutron irradiation are reported. The influence of 179m1Hf on the Hf composition changing dynamics and the process of transmutants’ (Ta, W) generation were determined. The effect of these processes on the absorbing properties of Hf, which inevitably predetermine the lifetime of the detector and its ability to generate a signal, is estimated.

One-dimensional semiconducting HfxZn1−xO nanorods and their photoswitching characteristics

Abstract Hafnia zinc oxide (HfxZn1−xO) nanorod-like structures were processed for photoswitching applications through a facile chemical strategy. Their crystalline structure and phase purity were examined by X-ray diffraction and Raman analysis. The evolution of HfxZn1−xO in rod-like configuration was inferred through scanning and transmission electron microscopy. The band gap values of HfxZn1−xO were estimated using Tauc's plot to be around 2.89–3.11 eV. The association of multiple defects within the hafnia based nanorods was further substantiated through luminescence results via sub-band signals in near visible region. Nyquist and bode plots of HfxZn1−xO nanorods were extracted from the electrochemical impedance spectroscopic results to evaluate the role of grain boundaries on their conductivity values. The electrical properties of HfxZn1−xO nanorods including their carrier density were estimated by capacitance vs. voltage (1/C2 vs. V) measurements. The photoswitching potential of n-HfxZn1−xO was investigated by spin casting the nanostructures on p-Si and investigating the diode's charge transfer characteristics. The Hf composition in the respective diode architecture was found to influence their corresponding photocurrent values.

Petrogenesis of the late Mesozoic highly fractionated I-type granites in the Luanchuan district: implications for the tectono-magmatic evolution of eastern Qinling

Late Mesozoic granites are extensively distributed in the Luanchuan district of eastern Qinling and can be divided into two types: Late Jurassic to Early Cretaceous granites (ore-related plutons) and Late Cretaceous granites (Laojunshan batholith). This study presents new geochemical and zircon U-Pb-Hf isotopic data from the Shibaogou and Yuku plutons to provide robust constraints on the petrogenesis and tectonic significance of the late Mesozoic granites in the Luanchuan district. Zircon U-Pb dating results yielded weighted mean 206Pb/238U ages of 149.1 ± 0.8 Ma and 150.5 ± 0.8 Ma, which were interpreted as the crystallization ages of the Shibaogou and Yuku plutons, respectively. We propose that the late Mesozoic granites contain high concentrations of SiO2 and alkali elements (Na2O + K2O) and feature metaluminous to weakly peraluminous characteristics. Enrichment in light rare earth elements and large ion lithophile elements and depletion in high field strength elements are observed. Mineralogical and geochemical evidence reveal that the late Mesozoic granites are highly fractionated I-type granites with fractional crystallization of feldspar, plagioclase and accessory minerals (e.g., apatite and titanite or magnetite). Based on the Hf composition, we suggest that the parental magmas of the ore-related plutons were derived from remelting of the Taihua and Xiong’er groups with minor contributions of mantle-derived materials and that the Laojunshan batholith was generated by the hybridization of ancient crust- (Kuanping group) and mantle-derived components. Collectively, the above arguments indicates a tectonic transition from compression to post-collisional extension during the late Mesozoic, that was likely triggered by the continental collision of the North China Block and the Yangtze Block, which generated numerous contemporaneous granites and Mo-W-Pb-Zn-Ag-Au poly-metallic deposits.

Isotope Lu–Hf composition of detrital zircon from paragneisses of the Sharyzhalgai uplift: evidence for the Paleoproterozoic crustal growth

We present results of study of the trace-element and Lu–Hf isotope compositions of zircons from Paleoproterozoic high-grade metasedimentary rocks (paragneisses) of the southwestern margin of the Siberian craton (Irkut terrane of the Sharyzhalgai uplift). Metamorphic zircons are represented by rims and multifaceted crystals dated at ~1.85 Ga. They are depleted in either LREE or HREE as a result of subsolidus recrystallization and/or synchronous formation with REE-concentrating garnet or monazite. In contrast to the metamorphic zircons, the detrital cores are enriched in HREE and have high (Lu/Gd)n ratios, which is typical of igneous zircon. The weak positive correlation between 176Lu/177Hf and 176Hf/177Hf in the zircon cores evidences that their Hf isotope composition evolved through radioactive decay in Hf = the closed system. Therefore, the isotope parameters of these zircons can give an insight into the provenance of metasedimentary rocks. The Paleoproterozoic detrital zircon cores from paragneisses, dated at ~2.3–2.4 and 2.0–1.95 Ga, are characterized by a wide range of εHf values (from +9.8 to –3.3) and model age TC 2.8–2.0 Ga. The provenance of these detrital zircons included both rocks with juvenile isotope Hf parameters and rocks resulted from the recycling of the Archean crust with a varying contribution of juvenile material. Zircons with high positive εHf values were derived from the juvenile Paleoproterozoic crustal sources, whereas the lower εHf and higher TC values for zircons suggest the contribution of the Archean crustal source to the formation of their magmatic precursors. Thus, at the Paleoproterozoic stage of evolution of the southwestern margin of the Siberian craton, both crustal recycling and crustal growth through the contribution of juvenile material took place. On the southwestern margin of the Siberian craton, detrital zircons with ages of ~2.3–2.4 and 1.95–2.0 Ga are widespread in Paleoproterozoic paragneisses of the Irkut and Angara–Kan terranes and in terrigenous rocks of the Urik–Iya graben, which argues for their common and, most likely, proximal provenances. In the time of metamorphism (1.88–1.85 Ga), the age of Paleoproterozoic detrital zircons (2.4–2.0 Ga), and their Lu–Hf isotope composition (εHf values ranging from positive to negative values) the paragneisses of the southwestern margin of the Siberian craton are similar to the metasedimentary rocks of the Paleoproterozoic orogenic belts of the North China Craton. In the above two regions, the sources of detrital zircons formed by both the reworking of the Archean crust and the contribution of juvenile material, which is evidence for the crustal growth in the period 2.4–2.0 Ga.

Timing and origin of migmatitic gneisses in south Karakoram: Insights from U–Pb, Hf and O isotopic record of zircons

The timing and origin of partial melting in collision belts is crucial to understand the thermotectonic evolution and the relationship between HT metamorphism and magmatism in over-thickened crust. In the present study, we used the in-situ isotopic (Hf, O and U–Pb) record of zircons to investigate the timing and origin of migmatitic gneisses exposed in the core of the Dassu dome in south Karakoram. The new U–Pb zircon dating identified the Proterozoic inherited cores (1.8–1.9Ga and 2.3–2.5Ga) surrounded by a Neogene overgrowth with ages ranging from ∼6 to ∼20Ma. These ages imply that the partial melting in the Karakoram Metamorphic Complex lasted from >20Ma to ∼6Ma and can be correlated with the Miocene magmatism in the adjacent Baltoro region. Oxygen isotopic data from Proterozoic inherited cores (1.8–1.9Ga) and Neogene overgrowths are indistinguishable and generally vary from 8‰ to 9.5‰. These values are slightly higher than the most igneous zircons (6.5–8‰, Valley et al., 2005) indicating an igneous precursor with heavy initial O composition that later might have equilibrated with low temperature environment or some involvement of supracrustal material is likely. However, a few low U/Th, relatively old inherited cores (2.3–2.5Ga) showed mantle-like (δ18O=5.3±0.6‰, Valley et al., 2005) values of δ18O=5.5±2.7‰. The present-day weighted mean εHf (0) of the Proterozoic inherited cores ranges from −50±1.0 to −44.3±1.2. In contrast, the Neogene rims are 15–20 ε-units higher than the inherited core with present-day εHf (0)=−30.6±0.9. This implies that the Hf composition of the Neogene overgrowth is not controlled exclusively by the dissolution of the inherited cores and that contamination by external melts is likely. We suggest a contribution from the Neogene, less-evolved magmatism in the Baltoro region (εHf (0)=∼−4 to −10). The elevated oxygen composition is not consistent with the contribution from pristine mantle-derived magmas. The observed homogeneous and uniform Hf–O isotopic composition of the Proterozoic inherited cores suggest their derivation from mildly evolved infracrustal sources with minor input from supracrustal material. The older inherited zircons (2.3–2.5Ga) were precipitated from juvenile mantle derived magmas.

广义化的电荷分解分析(GCDA)方法

电荷分解分析(CDA)是一种重要的深入研究电荷转移问题的方法。本文对CDA进行了介绍，阐述了计算中需要注意的问题，并提出了一种新的CDA形式，称为广义化的电荷分解分析(GCDA)。在HF、DFT级别GCDA与CDA等价，但GCDA能更好地用于后HF计算，而且还明确考虑了开壳层时的计算形式。通过以OC-BH3和顺式二氯二胺合铂体系作为测试实例，我们发现各种理论级别下GCDA的结果都较为合理且定性相符，但在定量上有所区别，特别是d项存在大体趋势：低HF成份的泛函 > 高HF成份的泛函 > HF ≥ MP2 > CCSD。文中还对GCDA计算时基组的选择进行了讨论。 Charge decomposition analysis (CDA) is an important method to study charge transfer problems in depths. In this paper, we introduced CDA method, elucidated the issues that needed attention in the calculation, and presented a new form of CDA, which was called GCDA. At HF and DFT levels, GCDA is equivalent to CDA, while GCDA is more applicable at post-HF level, and meantime its open-shell form is explicitly considered. By taking OC-BH3 and cis-dichlorodiamine as test cases, we find the GCDA results at various theoretical levels are reasonable and qualitatively consistent, but differ quantitatively; in particular, a rough trend exists in the d term: Functional with low HF composition > Functional with high HF composition > HF ≥ MP2 > CCSD. The paper also discussed the choice of basis-set in GCDA calculation.

Age and origin of post collision Baltoro granites, south Karakoram, North Pakistan: Insights from in-situ U–Pb, Hf and oxygen isotopic record of zircons

Abstract Origin of post collision plutonism is critical to understand the tectonothermal evolution of the over thickened continental crust in collision zones. This has proven difficult to reconcile with the conventional whole rock geochemical and field based studies alone. We report in-situ study of zircon U–Pb, Hf and O isotopes from five samples of the Baltoro Plutonic Unit (BPU) in south Karakoram. The plutonic unit is the western part of the southern Asian margin of the India–Asia convergent zone. Baltoro granites and a biotite-rich enclave yielded similar and overlapping U–Pb ages ranging from 26 to 15 Ma. Hafnium isotopic composition (eHf (0)) is very heterogeneous ranging from − 17.1 to + 4.4 while the oxygen isotopic composition of the granites is homogeneous with mean δ18O ranging from 7.2 to 9.4‰. Based on U–Pb geochronology and Hf–O isotopic composition, the involvement of two main sources is suggested (1) Cretaceous calc-alkaline Karakoram crust and (2) Karakoram gneisses. Moreover, possible involvement of metasomatized Asian lithospheric mantle is supported by elevated oxygen composition of granites and identical Hf composition of biotite-rich enclave to the mantle derived Baltoro lamprophyre. However, direct contribution from juvenile pristine mantle is unlikely as no juvenile mantle type Hf and oxygen values were obtained. This also precludes the involvement of southward juvenile arc related component of Kohistan–Ladakh batholith. Our new U–Pb and Hf data are comparable to the Mesozoic Karakoram batholith, Miocene two-mica leucogranites in the Pangong Range and magmatism from the Lhasa terrane in south Tibet, suggesting a genetic link between the Karakoram and the rocks to the east. This magmatic event is best explained by lower crust partial melting promoted by both thermal equilibration following crustal thickening and heat advection by ultrapotassic magmas associated with the breakoff of the Indian continental margin.