Xiaoxia Duan

Mesozoic molybdenum deposits in the East Xingmeng orogenic belt, northeast China: characteristics and tectonic setting

Numerous molybdenum (Mo) ore deposits have been discovered in the East Xingmeng orogenic belt (East Central Asian orogenic belt), over the past 10 years, and this region is becoming one of the worlds most important Mo production areas. It contains 6.18 Mt of proven Mo metal reserves, which accounts for 30% of the total proven Chinese Mo reserves. The ore district includes 37 deposits and 15 occurrences, with three major Mo ore types, that is porphyries, skarns, and hydrothermal veins. The latter can be subdivided into quartz- and volcanic hydrothermal-vein types. With the exception of the Ordovician Duobaoshan porphyry Cu–Mo deposit (477 Ma), all the East Xingmeng Mo deposits formed during the Mesozoic. Re–Os dating of molybdenite has documented three episodes of Mo mineralization: Early Triassic (248–242 Ma), Jurassic (178–146 Ma), and Early Cretaceous (142–131 Ma). Early Triassic Mo deposits are distributed along the northern margin fault of the North China Craton (NCC) and include porphyry and quartz vein types. They are characterized by the association of Mo + Cu. Jurassic Mo deposits are mainly distributed in the eastern area and include porphyry, quartz vein, and skarn types. They are typified by Mo alone and/or the association of Mo, Pb, and Zn. Cretaceous Mo deposits are distributed in all areas and include porphyry and volcanic hydrothermal vein types. Similar to the Jurassic ores, they are simple Mo or Mo + Pb + Zn deposits. Volcanic hydrothermal vein deposits are characterized by an association of molybdenum and uranium. The Triassic Mo deposits formed in a syn-collision setting between the Siberian and North China plates. The Jurassic Mo deposits formed in a compressional setting, which was probably triggered by the westward subduction of the palaeo-Pacific plate. The Early Cretaceous Mo deposits are linked to a tectonic regime of lithosphere thinning, which was caused by delamination of thickened lithosphere. However, the Mo deposits in the Erguna terrane of the northwest Xingmeng orogenic belt may be related to the evolution of the Okhotsk Ocean.

Geochronology of magmatism and mineralization of the Daheishan giant porphyry molybdenum deposit, Jilin Province, Northeast China: constraints on ore genesis and implications for geodynamic setting

Daheishan giant porphyry Mo deposit is located in the Lesser Xing’an–Zhangguangcai Ranges, Jilin Province, NE China. Mineralization is closely related to the Daheishan intrusive complex, which can be divided into Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry. Four stages of mineralization are distinguished, based on the cross-cutting relationships of mineralized veins. LA-ICPMS zircon U-Pb analysis yields 206Pb/238U ages of 177.9 ± 2.3 Ma for the Changganglin biotite granodiorite, 169.9 ± 2.3 Ma for the Qiancuoluo biotite granodiorite, and 166.6 ± 4.0 Ma for the Qiancuoluo granodioritic porphyry. Hydrothermal fluids responsible for mineralization evolved from different magmas. Six molybdenite samples yield Re-Os model ages of ~167 Ma. Muscovite from the last mineralization stage gives a 40Ar/39Ar plateau age of 163.6 ± 0.9 Ma. Geochronology data indicate that the entire magmatic system lasted for about 10 million years, and the total duration of hydrothermal activity was less than 4 million years. The εHf(t) values of zircons obtained from the Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry range from 4.5 to 9.1, 5.7 to 10.9, and 4.4 to 7.1, respectively, indicating that they were mainly derived from the depleted mantle, although contaminated by crustal materials to a greater or lesser extent. The formation of the Daheishan porphyry Mo deposit was temporally and spatially related to the amalgamation of Jiamusi Massif and Songliao terrane in the Palaeo-Pacific Ocean regime. Regional Hf isotopic compositions of zircon suggest an episode of crustal growth in the Phanerozoic in the Lesser Xing’an–Zhangguangcai Ranges. Regional Mo mineralization ages suggest a peak of porphyry Mo mineralization in the Jurassic in the Lesser Xing’an-Zhangguangcai Ranges.

Genesis of the Chehugou Mo-bearing granitic complex on the northern margin of the North China Craton: geochemistry, zircon U–Pb age and Sr–Nd–Pb isotopes

The Chehugou granite-hosted molybdenum deposit is typical of the Xilamulun metallogenic belt, which is an important Mo–Ag–Pb–Zn producer in China. A combination of major and trace element, Sr and Nd isotope, and zircon U–Pb isotopic data are reported for the Chehugou batholith to constrain its petrogenesis and Mo mineralization. The zircon SIMS U–Pb dating yields mean ages of 384.7 ± 4.0 Ma and 373.1 ± 5.9 Ma for monzogranite and syenogranite and 265.6 ± 3.5 Ma and 245.1 ± 4.4 Ma for syenogranite porphyry and granite porphyry, respectively. The Devonian granites are calc-alkaline with K 2 O/Na 2 O ratios of 0.44–0.52, the Permian granites are alkali-calcic with K 2 O/Na 2 O ratios of 1.13–1.25, and the Triassic granites are calc-alkaline and alkali-calcic rocks with K 2 O/Na 2 O ratios of 0.78–1.63. They are all enriched in large-ion lithophile elements (LILEs) and depleted in high-field-strength elements (HFSEs) with negative Nb and Ta anomalies in primitive mantle-normalized trace element diagrams. They have relatively high Sr (189–1256 ppm) and low Y (3.87–5.43 ppm) concentrations. The Devonian granites have relatively high initial Sr isotope ratios of 0.7100–0.7126, negative ɛ Nd ( t ) values of −12.3 to −12.4 and 206 Pb/ 204 Pb ratios of 16.46–17.50. In contrast, the Permian and Triassic granitoids have relatively low initial 87 Sr/ 86 Sr ratios (0.7048–0.7074), negative ɛ Nd ( t ) values of −10.1 to −13.1 and 206 Pb/ 204 Pb ratios of 17.23–17.51. These geochemical features suggest that the Devonian, Permian and Triassic Chehugou granitoids were derived from ancient, garnet-bearing crustal rocks related to subduction of the Palaeo-Asian Ocean and subsequent continent–continent collision between the North China and Siberian plates.

U–Pb and Re–Os geochronology of the Haolibao porphyry Mo–Cu deposit, NE China: implications for a Late Permian tectonic setting

New geochronological data for the Haolibao porphyry Mo–Cu deposit, NE China, yieldn Permian crystallization zircon U–Pb ages of 278 ± 5 Ma for granite and 267 ± 10 Ma for then granite porphyry that hosts the Mo–Cu mineralization, and four Re–Os molybdenite agesn yield an isochron age of 265 ± 3 Ma. These ages disagree with the previous K–Ar agen determinations that suggest a correlation of intrusive rocks of the Haolibao area with then Yanshanian intrusive rocks of Cretaceous age. The mineralizations at the Haolibao area mayn be related to the tectonic–magmatic activity caused by collisional events between then North China Plate and Mongolian terranes during the Permian. The occurrence of then Haolibao plutonic rocks indicates that the Palaeo-Asian-Mongolian Ocean closed during then Permian along the Xilamulun River suture.

Triassic magmatism and Mo mineralization in Northeast China: geochronological and isotopic constraints from the Laojiagou porphyry Mo deposit

The Laojiagou Mo deposit is a newly discovered porphyry Mo deposit located in the Xilamulun Mo metallogenic belt, Northeast China. Mo mineralization mainly occurred within the monzogranite and monzogranite porphyry. Re–Os isochron dating of molybdenites indicate a mineralization age of 234.9 ± 3.1 Ma. Zircon LA–ICP–MS U–Pb analysis for monzogranite porphyry and monzogranite yield 206Pb/238U ages of 238.6 ± 1.8 and 241.3 ± 1.5 Ma, respectively, indicating that Laojiagou Mo mineralization is related to Middle Triassic magmatism. Hf isotopic compositions of zircons from both monzogranite porphyry and monzogranite are characterized by positive εHf(t) values [εHf(t) = 2.9–7.3 and 1.5–7.9, respectively] and young TDM2 model ages, which implies that the magma was derived from juvenile crust created during accretion of the Central Asian Orogenic Belt (CAOB). Identification of the Laojiagou Mo deposit adds another important example of Triassic Mo mineralization in the Xilamulun Mo metallogenic belt where most Triassic Mo deposits in northeast China cluster around the northern margin of North China Craton. Based on the regional geological setting and geochronological and Hf isotope characteristics, we propose that Triassic Mo deposits and related magmatic rocks in northeast China formed during the last stages of evolution of the CAOB. These deposits formed during post-collisional extension after the closure of the Palaeo-Asian Ocean and amalgamation of the North China–Mongolian Block with the Siberian Craton.

Controlled synthesis and phase transformation of ferrous nanowires inside carbon nanotubes

Abstract Carbon nanostructures filled with Fe were synthesized. It was found that both the shape and the phase of the carbon nanocapsulate may be controlled during the growth, and controlled ferrous amorphous–crystalline phase transformation may be realized via electron beam irradiation. Since an electron beam may be focused into a nanoscale probe, this method may in principle be used for fabricating amorphous–crystalline heterostructures inside carbon nanotubes.

Late Jurassic granitoids in the Xilamulun Mo belt, Northeastern China: geochronology, geochemistry, and tectonic implications

ABSTRACT The Xilamulun Mo belt of Northeastern China, located in the southeastern segment of the Central Asia Orogenic Belt (CAOB), is composed of large deposits of porphyry Mo and quartz-vein-type Mo, which are related to Mesozoic granitoids. Previous studies led to the conclusion that all granitoids in the region formed during the Cretaceous and Triassic, but our new laser ablation inductively coupled plasma mass spectrometry U–Pb zircon dating of magmatic zircons from five samples of four mineralized plutons (Nailingou, Longtoushan, and Hashitu granites and Erbadi and Hashitu granite porphyries) reveals that these range in age from 143.8 ± 1.2 to 149.5 ± 1.0 Ma. These granites show post-collisional (A-type) geochemical characteristics (e.g. enrichment in total alkali, LILE, and LREE and depletion in Eu, Ba, P, and Nb). The Erbadi, Longtoushan, Hashitu, and Longtoushan granitoids exhibit moderately positive Hf isotopic compositions (εHf(t) = −0.3 to 10.2), indicating that granitic magmas may reflect mixtures of mantle melts and continental crust. These mineralized granites were all emplaced along a major fault over a time span of ~6 million years during the Late Jurassic. We conclude that igneous activity and mineralization resulted from the rollback of the subducted Palaeo-Pacific plate beneath Eurasia. Confirming that the Late Jurassic granitic intrusives are related to the Mo mineralization is useful for understanding the Mesozoic tectonic evolution of the Xilamulun Mo belt and also has significant implications for the regional exploration of ores.

Transmission electron microscopy studies of the effect of A-site cation size mismatch and disorder on charge ordering behavior in (La1−xYx)0.5(Ca1−ySry)0.5MnO3

The effects of A-site cation mismatch and disorder on the charge ordering (CO) behavior in the manganites (La1−xYx)0.5(Ca1−ySry)0.5MnO3 have been studied by transmission electron microscopy. The presence of the size mismatch and disorder suppresses the CO transition. Incommensurate CO modulations are observed in three samples with 0⩽σ2⩽0.003. Structural models, based on the selected area electron diffraction and high-resolution electron microscopy observation, are suggested for such kinds of incommensurate modulations.

TEM studies of an incommensurate charge ordering modulation in La0.5Ca0.5MnO3

Abstract Electron energy-loss spectroscopy in the transmission electron microscope has been used to determine the valence state of manganese in La 0.5 Ca 0.5 MnO 3 at room temperature and at 93 K. An incommensurate charge ordering modulation in La 0.5 Ca 0.5 MnO 3 was detected by transmission electron microscopy. A structural model, based on the selected area electron diffraction and high-resolution electron microscopy observation, is proposed for the incommensurate modulation.

Charge-ordering modulation observed in the (La0.5Mn0.5)MnO3 phase of the multiphased manganite La0.9Sn0.1MnO3 at room temperature

At room temperature, the lattice image of a modulated structure associated with charge ordering has been observed in the (La0.5Mn0.5)MnO3 phase of La0.9Sn0.1MnO3, which is composed of two-type phases: ABO3 and A2B2O7. Results of electron energy loss spectroscopy and energy dispersive x-ray spectroscopy show that the need of the chemical balance and small A-site radius for the (La0.5Mn0.5)MnO3 phase are the main reasons for the appearance of charge ordering stripes.