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Genetic load refers to the accumulated and potentially life-threatening deleterious mutations in populations. Understanding the mechanisms underlying genetic load variation of transposable elements (TEs), one major large-effect mutations, during range expansion is an intriguing question in biology. Here, we used 1,115 globally natural accessions ofArabidopsis thaliana, to study the driving forces of TE load variation during its range expansion. The TE load increased with range expansion, especially in the recently established Yangtze River basin population. The effective population size explained 62.0% of the variance in TE load, and high transposition rate and positive selection or hitch-hiking effect contributed to the accumulation of TEs in the expanded populations. We genetically mapped the candidate causal genes or TEs and revealed the genetic architecture of TE load. Overall, this study reveals the variation in the genetic load of TEs during Arabidopsis expansion and highlights the causes of TE load variation.

The early Paleozoic tectonic evolution of the Xing’an–Mongolian Orogenic Belt is dominated by two oceanic basins on the northwestern and southeastern sides of the Xing’an Block, i.e., the Xinlin–Xiguitu Ocean and the Nenjiang Ocean. However, the early development of the Nenjiang Ocean remains unclear. Here, we present zircon U–Pb geochronology and whole-rock elemental and Sr–Nd isotopic data on the gabbros in the Xinglong area together with andesitic tuffs and basalts in the Duobaoshan area. LA-ICP-MS zircon U–Pb dating of gabbros and andesitic tuffs yielded crystallization ages of 443–436 ​Ma and 452–451 ​Ma, respectively. The Early Silurian Xinglong gabbros show calc-alkaline and E-MORB affinities but they are enriched in LILEs, and depleted in HFSEs, with relatively low U/Th ratios of 0.18–0.36 and eNd(t) values of −1.6 to +0.5. These geochemical features suggest that the gabbros might originate from a mantle wedge modified by pelagic sediment-derived melts, consistent with a back-arc basin setting. By contrast, the andesitic tuffs are characterized by high MgO (>5 ​wt.%), Cr (138–200 ​ppm), and Ni (65–110 ​ppm) contents, and can be termed as high-Mg andesites. Their low Sr/Y ratios of 15.98–17.15 and U/Th values of 0.24–0.25 and moderate (La/Sm)n values of 3.07–3.26 are similar to those from the Setouchi Volcanic Belt (SW Japan), and are thought to be derived from partial melting of subducted sediments, and subsequent melt-mantle interaction. The Duobaoshan basalts have high Nb (8.44–10.30 ​ppm) and TiO2 contents (1.17–1.60 ​wt.%), typical of Nb-enriched basalts. They are slightly younger than regional adakitic rocks and have positive eNd(t) values of +5.2 to +5.7 and are interpreted to be generated by partial melting of a depleted mantle source metasomatized by earlier adakitic melts. Synthesized with coeval arc-related igneous rocks from the southeastern Xing’an Block, we propose that the Duobaoshan high-Mg andesitic tuffs and Nb-enriched basalts are parts of the Late Ordovician and Silurian Sonid Zuoqi–Duobaoshan arc belt, and they were formed by the northwestern subduction of the Nenjiang Ocean. Such a subduction beneath the integrated Xing’an–Erguna Block also gave rise to the East Ujimqin–Xinglong igneous belt in a continental back-arc basin setting. Our new data support an early Paleozoic arc–back-arc model in the northern Great Xing’an Range.

Although the Early Paleozoic tectonic framework of northern West Junggar is essential for understanding accretionary processes in the southwestern Central Asian Orogenic Belt, this setting is still not well understood. In order to address this issue, we employed detailed geochronological, geochemical and Sr-Nd-Hf-Os isotope analyses on the Hoboksar ophiolitic melange in northern West Junggar. The Hoboksar ophiolitic melange mainly consists of serpentinized peridotites, pyroxenites, gabbros, diabase, cherts, marbles, volcanic and pyroclastic rocks. It is characterized by a “block-in-matrix” structure with serpentinized peridotites as the matrix which is crosscut by later diorite porphyry and rhyolitic porphyry. Olivines and spinels in these serpentinized peridotites show high Fo# and Cr#, respectively. The clinopyroxenes in the pyroxenites exhibit high Mg#, low Al2O3 and Cr2O3. The serpentinized peridotites have extremely low rare-earth element (REE) abundances, U-shaped to flat REE patterns and positive Eu anomalies. Their particularly low Re/Os, initial 187Os/188Os and γOs(t) imply that they could represent residual phases after partial melting of upper mantle. The gabbros and diabases display slight fractionation between light REE and heavy REE, negligible Eu anomalies, depletion in Rb, Nb and Ta, enrichment in Th and U, low initial 87Sr/86Sr and positive eNd(t). The mineral and whole-rock geochemical and isotopic compositions of these ultramafic-mafic rocks demonstrate that the Hoboksar ophiolitic melange originated from a depleted mantle in a fore-arc supra-subduction zone (SSZ) setting. Zircon U Pb dating on diorite porphyry and rhyolitic porphyry yields weighted mean 206Pb/238U ages of 435 ± 4 Ma and 441 ± 2 Ma, respectively, postdating the closure of an ancient ocean represented by the Hoboksar ophiolite. These later intrusions resemble adakitic rocks with high Sr/Y. They exhibit mild depletion in Nb and Ti, low initial 87Sr/86Sr, positive eNd(t) and zircon eHf(t). Therefore the diorite porphyry and rhyolitic porphyry likely derived from juvenile lower crust. Based on our new data and other geologic evidence, we propose that the ancient Hoboksar Ocean resided between two Paleozoic arcs in northern West Junggar during the Early Ordovician, and this ocean was closed before 440 Ma. The emplacement of adakitic stitching intrusions implies a back-arc extensional setting that may be due to (present-day) northward subduction of the Junggar-Balkhash oceanic slab during the Early Silurian.

According to the less-is-more hypothesis, gene loss is an engine for evolutionary change. Loss-of-function (LoF) mutations resulting in the natural knockout of protein-coding genes not only provide information about gene function but also play important roles in adaptation and phenotypic diversification. Although the less-is-more hypothesis was proposed two decades ago, it remains to be explored on a large scale. In this study, we identified 60,819 LoF variants in 1071 Arabidopsis (Arabidopsis thaliana) genomes and found that 34% of Arabidopsis protein-coding genes annotated in the Columbia-0 genome do not have any LoF variants. We found that nucleotide diversity, transposable element density, and gene family size are strongly correlated with the presence of LoF variants. Intriguingly, 0.9% of LoF variants with minor allele frequency larger than 0.5% are associated with climate change. In addition, in the Yangtze River basin population, 1% of genes with LoF mutations were under positive selection, providing important insights into the contribution of LoF mutations to adaptation. In particular, our results demonstrate that LoF mutations shape diverse phenotypic traits. Overall, our results highlight the importance of the LoF variants for the adaptation and phenotypic diversification of plants.

The West Junggar terrane (WJT) is an outstanding laboratory for studying the tectonic evolution of the Junggar–Balkhash Ocean, because it contains widespread Paleozoic magmatism in different tectonic settings. We attempt to reconstruct the tectono-magmatic evolution of WJT through U–pb analysis of detrital zircons from three modern river sand samples from the Harabura, Baibuxie, and Aletengyemule rivers in the Barleik Mountains of the central WJT. A total of 232 concordant spots show Th/U ratios of 0.14–1.69, typical of igneous origin, and they contain abundant Paleozoic (96%) and few Precambrian (4%) ages, with major age populations at 450–530, 400–430, 320–380, and 265–320 Ma. The first two groups may be derived from the early subduction- and accretion-related magmatic rocks of the WJT, whereas the third group is congruent with magmatic activities related to the final subduction and basin-filling processes within a framework of the remnant Junggar–Balkhash Ocean. By combining with the regional d...

The Junggar–Balkhash Ocean was a major branch of the southern Paleo-Asian Ocean. The timing of its closure is important for understanding the history of the Central Asian Orogenic Belt. New sedimentological and geochronological data from the Late Paleozoic volcano-sedimentary sequences in the Barleik Mountains of West Junggar, NW China, help to constrain the closure time of the Junggar–Balkhash Ocean. Tielieketi Formation (Fm) is dominated by littoral sediments, but its upper glauconite-bearing sandstone is interpreted to deposit rapidly in a shallow-water shelf setting. By contrast, Heishantou Fm consists chiefly of volcanic rocks, conformably overlying or in fault contact with Tielieketi Fm. Molaoba Fm is composed of parallel-stratified fine sandstone and sandy conglomerate with graded bedding, typical of non-marine, fluvial deposition. This formation unconformably overlies the Tielieketi and Heishantou formations and is conformably covered by Kalagang Fm characterized by a continental bimodal volcanic association. The youngest U–Pb ages of detrital zircons from sandstones and zircon U–Pb ages from volcanic rocks suggest that the Tielieketi, Heishantou, Molaoba, and Kalagang formations were deposited during the Famennian–Tournaisian, Tournaisian–early Bashkirian, Gzhelian, and Asselian–Sakmarian, respectively. The absence of upper Bashkirian to Kasimovian was likely caused by tectonic uplifting of the West Junggar terrane. This is compatible with the occurrence of coeval stitching plutons in the West Junggar and adjacent areas. The Junggar–Balkhash Ocean should be finally closed before the Gzhelian, slightly later or concurrent with that of other ocean domains of the southern Paleo-Asian Ocean.

The Paleozoic accretionary orogenesis and continental crustal growth in Central Asia are thought to have close relationship with the evolution of the Paleo-Asian Ocean (PAO). The well-exposed plutons in the northern Barleik Mountains of the West Junggar region, NW China, may provide essential insights into the evolution of the Junggar Ocean, a branch of the PAO, and mechanism of continental crustal growth. Our work on the Barleik plutons indicates an early suite of 324–320 Ma diorite and a late suite of 314–259 Ma quartz syenite and granitic porphyry. All the plutons are characterized by high-K calc-alkaline to shoshonitic signatures, varying depletion in Nb, Ta, Sr, P, Eu, and Ti, low initial 87Sr/86Sr ratios (0.70241–0.70585), strongly positive eNd(t) values (+ 5.7–+7.7), and young one-stage Nd model ages (390–761 Ma), suggesting that they resulted from different batches of magma that were produced by fractional crystallization of a metasomatized mantle source with minor crustal contamination. The diorite is coeval with the youngest arc magmatic rocks, indicating a subduction-related origin. By contrast, the quartz syenite and granitic porphyry are geochemically similar to A2-type granites, with high Zr, Ga, and FeOT/[FeOT + MgO], and are coeval with the widespread plutons in the West Junggar. This, together with the occurrence of Late Carboniferous fluvial deposits and the lack of < 320 Ma ophiolitic and subduction-related metamorphic lithologies, definitively indicates a post-collisional setting after the closure of the Junggar Ocean. Slab breakoff accompanied by asthenospheric upwelling and basaltic underplating is a possible geodynamic process that is responsible for the post-collisional magmatism and vertical crustal growth in the region. Thus a tectonic switch from subduction to post-collision started at the end of the Early Carboniferous (~ 320 Ma), probably as a result of the final closure of the Junggar Ocean.

Significance The mechanisms underlying rapid adaptation to changing environments in species with reduced genetic variation, referred to as the “genetic paradox of invasion,” are unknown. We report that transposable elements (TEs) are highly enriched in the gene promoter regions of Capsella rubella compared with its outcrossing sister species Capsella grandiflora. We also show that a number of polymorphic TEs in C. rubella are associated with changes in gene expression. Frequent TE insertions at FLOWERING LOCUS C of C. rubella affect flowering-time variation, an important life history trait correlated with fitness. These results indicate that TE insertions drive rapid phenotypic variation, which could potentially help adapting to novel environments in species with limited genetic variation., Rapid phenotypic changes in traits of adaptive significance are crucial for organisms to thrive in changing environments. How such phenotypic variation is achieved rapidly, despite limited genetic variation in species that experience a genetic bottleneck is unknown. Capsella rubella, an annual and inbreeding forb (Brassicaceae), is a great system for studying this basic question. Its distribution is wider than those of its congeneric species, despite an extreme genetic bottleneck event that severely diminished its genetic variation. Here, we demonstrate that transposable elements (TEs) are an important source of genetic variation that could account for its high phenotypic diversity. TEs are (i) highly enriched in C. rubella compared with its outcrossing sister species Capsella grandiflora, and (ii) 4.2% of polymorphic TEs in C. rubella are associated with variation in the expression levels of their adjacent genes. Furthermore, we show that frequent TE insertions at FLOWERING LOCUS C (FLC) in natural populations of C. rubella could explain 12.5% of the natural variation in flowering time, a key life history trait correlated with fitness and adaptation. In particular, we show that a recent TE insertion at the 3′ UTR of FLC affects mRNA stability, which results in reducing its steady-state expression levels, to promote the onset of flowering. Our results highlight that TE insertions can drive rapid phenotypic variation, which could potentially help with adaptation to changing environments in a species with limited standing genetic variation.

The subduction-accretionary evolution of the southeastern margin of the Central Asian Orogenic Belt (CAOB), consisting of the northern North China Craton, Bainaimiao arc, and Ondor Sum accretionary complex from south to north, is still not well understood. In order to clarify the Early Paleozoic subduction process in the southeastern margin of the CAOB, we conducted geochronological, geochemical, and Sr-Nd-Hf isotope analyses of the Zhangjiatun igneous complex rocks. The Zhangjiatun complex is composed of hornblende gabbro, quartz diorite, and tonalite. Zircon U-Pb dating of the complex yields ages ranging from 486 Ma to 440 Ma. We interpret this result as indicating Early Paleozoic arc magmatism along the southeastern margin of the CAOB. Late Cambrian to Early Ordovician mafic-intermediate intrusions have low-K tholeiitic compositions characterized by low (La/Yb)N (0.4–1.2) and initial 87Sr/86Sr (0.70439–0.70447) ratios, positive eNd(t) (+6.5 to +7.6), and eHf(t) (+13.5 to +19.0) values. The geochemical values indicate the rocks to be of N-MORB affinities, likely generated by melt differentiation from a depleted mantle. An Early Silurian tonalite exhibits oceanic plagiogranite signatures, expressed by high Na2O, and low K2O, Rb, and total REE contents. The tonalite also yields high (La/Yb)N values, low Sr/Y and initial 87Sr/86Sr (0.70345) ratios, and positive eNd(t) (+3.3) and eHf(t) (+8.0 to +12.5) values. Geochemical modelling suggests that the tonalite may have originated from hydrous melting of hornblende gabbro with a minor contribution from melting of oceanic sediments. The Late Cambrian to Early Ordovician mafic-intermediate intrusions with MORB characteristics likely resulted from initial intra-oceanic subduction along the southern margin of the Paleo-Asian Ocean. We interpret the Early Silurian tonalite to have been generated as the arc became fully developed. We further suggest that the southeastern margin of the CAOB has involved two subduction systems during the Early Paleozoic: a northern south-dipping intra-oceanic arc and a southern north-dipping continental arc.

Transposable elements (TEs) are mobile genetic elements with very high mutation rates that play important roles in shaping genome architecture and regulating phenotypic variation. However, the extent to which TEs influence the adaptation of organisms in their natural habitats is largely unknown. Here, we scanned 201 representative resequenced genomes from the model plant Arabidopsis thaliana and identified 2,311 polymorphic TEs from noncentromeric regions. We found expansion and contraction of different types of TEs in different A. thaliana populations. More importantly, we identified two TE insertions that are likely candidates to play a role in adaptive evolution. Our results highlight the importance of variations in TEs for the adaptation of plants in general in the context of rapid global climate change.

As one of the important parts of the Central Asian Orogenic Belt, the Early–Middle Paleozoic subduction–accretion history of the West Junggar is still needed to be further constrained although major progress has been made in the past years. In particular, the geodynamic setting for Late Silurian–Early Devonian A-type granites and associated mafic to felsic magmatism in the northern West Junggar is still controversial. In this study, we report new geochronological and geochemical results for Middle Paleozoic plutons in the Xiemisitai-Saier Mountains, northern West Junggar, including undeformed peralkaline granite, alkali feldspar granite, monzogranite, quartz syenite, syenite, monzodiorite, diorite, and hornblende gabbro. These plutons crop out in the eastern segment of the Early–Middle Paleozoic Boshchekul–Chingiz arc and invade into Early–Middle Paleozoic marine volcanic and pyroclastic sequences. New and published zircon U–Pb ages indicate that these intrusions were emplaced during the Late Silurian–Middle Devonian (424–392 Ma). Late Silurian hornblende gabbro, diorite, and monzodiorite commonly contain abundant hornblendes and exhibit mantle-like Nb/Ta ratios (15.9–18.7), negligible Eu anomalies, with primitive Sr–Nd–Hf [I(Sr) = 0.70370–0.70375, eNd(t) = +5.1 to +6.0 and eHf(t) = +14.3 to +16.2] and radiogenetic Os (I(Os) = 0.2099–0.8795) isotopic signatures. They may be originated from a fluid metasomatized, H 2 O-rich and isotopically depleted mantle source and suffered some crustal contamination. Early–Middle Devonian calc-alkaline monzogranite and alkaline–peralkaline granitoids may have distinct origins. The monzogranite is I-type granite with high La/Yb ratios, depleted eNd(t) values (+5.1), and crust-like Nb/Ta ratios (8.5–8.9), which is suggested to be partial melt of juvenile lower crust containing massive hornblende ± garnet. The peralkaline–alkaline granitoids include A-type and highly fractionated I-type granites, which contain mafic–intermediate enclaves and chemically exhibit variable element ratios, analogical eNd(t) values (+5.1 to +6.2), and significantly high I(Os) value (2.1247). They are interpreted to be produced by fractional crystallization of the hybrid magma contributed from mantle and crustal sources. Based on our new data, along with other geological evidence, it is speculated that these A-type granites and associated mafic to felsic intrusions may occur in a post-collisional extension setting since the end-Silurian, after the initial amalgamation of the West Junggar terrane during the Middle–Late Silurian. On-going lithosphere extension during the Early–Middle Devonian would result in the rifting of newly amalgamated West Junggar and thus induce asthenosphere upwelling, which gave rise to the mantle-derived magmatism in the northern and southern West Junggar and juvenile oceanic crust in central West Junggar. It is suggested that the Middle Paleozoic is an important episode of crustal growth in the West Junggar.

Background Organisms need to adapt to keep pace with a changing environment. Examining recent range expansion aids our understanding of how organisms evolve to overcome environmental constraints. However, how organisms adapt to climate changes is a crucial biological question that is still largely unanswered. The plant Arabidopsis thaliana is an excellent system to study this fundamental question. Its origin is in the Iberian Peninsula and North Africa, but it has spread to the Far East, including the most south-eastern edge of its native habitats, the Yangtze River basin, where the climate is very different. Results We sequenced 118 A. thaliana strains from the region surrounding the Yangtze River basin. We found that the Yangtze River basin population is a unique population and diverged about 61,409 years ago, with gene flows occurring at two different time points, followed by a population dispersion into the Yangtze River basin in the last few thousands of years. Positive selection analyses revealed that biological regulation processes, such as flowering time, immune and defense response processes could be correlated with the adaptation event. In particular, we found that the flowering time gene SVP has contributed to A. thaliana adaptation to the Yangtze River basin based on genetic mapping. Conclusions A. thaliana adapted to the Yangtze River basin habitat by promoting the onset of flowering, a finding that sheds light on how a species can adapt to locales with very different climates. Electronic supplementary material The online version of this article (doi:10.1186/s13059-017-1378-9) contains supplementary material, which is available to authorized users.

Background In contrast to positive selection, which reduces genetic variation by fixing beneficial alleles, balancing selection maintains genetic variation within a population or species and plays crucial roles in adaptation in diverse organisms. However, which genes, genome-wide, are under balancing selection and the extent to which these genes are involved in adaptation are largely unknown. Results We performed a genome-wide scan for genes under balancing selection across two plant species, Arabidopsis thaliana and its relative Capsella rubella, which diverged about 8 million generations ago. Among hundreds of genes with shared coding-region polymorphisms, we find evidence for long-term balancing selection in five genes: AT1G35220, AT2G16570, AT4G29360, AT5G38460, and AT5G44000. These genes are involved in the response to biotic and abiotic stress and other fundamental biochemical processes. More intriguingly, for these genes, we detected significant ecological diversification between the two haplotype groups, suggesting that balancing selection has been very important for adaptation. Conclusions Our results indicate that beyond the well-known S-locus genes and resistance genes, many loci are under balancing selection. These genes are mostly correlated with resistance to stress or other fundamental functions and likely play a more important role in adaptation to diverse habitats than previously thought. Electronic supplementary material The online version of this article (doi:10.1186/s13059-017-1342-8) contains supplementary material, which is available to authorized users.

The late Carboniferous Dongwanzi Complex in the northern North China Craton is composed of intrusive pyroxenite, hornblendite, gabbro, and syenite. The mafic-ultramafic rocks of the complex exhibit typical cumulate textures, curved-upward REE patterns, and variable contents of compatible elements, suggesting a cumulate origin. The syenite shows Sr-Nd isotopic ratios similar to the mafic-ultramafic complex and positive Eu anomalies in the chondrite-normalized REE patterns, suggesting that the syenite may represent residual melt after significant fractional crystallization of mafic melt. The mafic-ultramafic cumulates have low HREE abundance and high (Tb/Yb)N (2.5–4.2) and Dy/Yb ratios (>2), indicating that they may have originated from melting of garnet peridotite in the mantle. The Dongwanzi Complex is characterized by a large variation in Sr-Nd isotopic composition, with ISr = 0.7035 to 0.7052 and eNd(t) = −4.0 to +5.2, which may be accounted for by mixing melts of depleted asthenospheric and enriched li...

We report here a Cambrian southward-subducting intra-oceanic arc system in the southern West Junggar, NW China, where an immature arc occurred initially on SSZ-type ophiolites and finally evolved into a more mature one. The immature arc is dominantly represented by Early–Middle Cambrian (∼510 Ma) low-K tholeiitic felsic rocks, whereas the mature arc is characterized by Late Cambrian (∼495 Ma) medium- and high-K calc-alkaline felsic and mafic rocks. The SSZ-type ophiolites show remarkable depletion of Nb and Ta and contain high-Cr spinel (Cr# > 0.6), resembling these formed in the forearc. Altogether, they record the initiation of subduction and transformation of crust during early subduction of the Paleo-Asian Ocean in the southern part of the Central Asian Orogenic Belt (CAOB). The subduction initiation might occur in the Early Cambrian (>515 Ma), as constrained by both the SSZ-type ophiolites (516 Ma) and the oldest arc plutons (515–509 Ma) that crosscut the ophiolites. The immature felsic plutons have high SiO 2 (>72 wt%) contents and variable MgO (0.42–1.49 wt%) and Mg# values (22–62). Crustal anatexis may be responsible for the genesis of those plutons and thus the transformation from oceanic to continental crust. These results, combined with regional data, convincingly indicate that it is one of the oldest intra-oceanic arc systems in the southern CAOB, which may mark the initial subduction of the Paleo-Asian Ocean in its southern part, much later than those reported in the north. An archipelago-type model is proposed for the evolution of the southern West Junggar and has implications for the development of the southern part of the CAOB.

The West Junggar, northwestern China, is located in the southwest of the Central Asian Orogenic Belt (CAOB) and consists of Paleozoic ophiolitic melanges, arcs and accretionary complexes. The Mayile Mountain ultramafic–mafic melange in the southern West Junggar is the northeastern part of the Mayile ophiolitic melange. The Mayile Mountain melange is represented by a ca. 30 km long, 5 km wide, north–northeast-striking serpentinite-matrix melange, which encloses serpentinized harzburgite, dunite, chromitite, wehrlite, clinopyroxenite, gabbro, rodingite, and chert blocks. It is overlain by the Middle Silurian greenschist facies and Early–Middle Devonian unmetamorphic volcano-sedimentary strata. Chemically, chromian spinel from peridotite and clinopyroxenite is similar to those of island arc lava and depleted peridotite from supra-subduction zone (SSZ). Clinopyroxene from the ultramafic–mafic rocks shows the affinities of island arc tholeiite and boninite. The ultramafic–mafic rocks also show the subduction-related geochemical signatures, such as flat REE patterns with slight LREE depletion ((La/Yb)N = 0.66–0.89), LILE enrichment and HFSE depletion. The ultramafic–mafic melange is crosscut by intrusions. Zircon U–Pb dating reveals four phases of magmatism: Late Cambrian (501–493 Ma), Early Ordovician (488–485 Ma), Early Silurian (444–439 Ma), and Late Carboniferous–Early Permian (318–296 Ma). The Late Cambrian gabbro, diorite and granite, Early Ordovician diorite and Early Silurian granodiorite intrude the melange in places and predate the overlying Middle Silurian and Early–Middle Devonian successions. They are I-type calc-alkaline and show strong island arc affinities, with LILE and LREE enrichment ((La/Yb)N = 3.77–21.45) and HFSE depletion. On the contrary, the Late Carboniferous–Early Permian I-type diorite, granodiorite and granite and A-type alkali-feldspar granite crosscut both the melange and overlying strata. They are coeval with the widespread post-collisional granitoids in the West Junggar. Our data for the melange and intrusions suggest that this melange might be a highly mixed SSZ-type ophiolitic melange generated in the earliest stage of south-dipping subduction–accretion during the Early–Middle Cambrian, and then an island arc was successively built in the south in the Late Cambrian (501–493 Ma), in the center in the Early Ordovician (488–485 Ma) and in the north in the Early Silurian (444–439 Ma), as a result of northward arc migration. In the Middle Silurian, the melange and island arc intrusions might be exposed and covered by deep or hemi-deep sea volcano-sedimentary strata in a back-arc setting, and they might have been accreted southward to another arc and continental margin before the Early–Middle Devonian. After the ocean was ultimately closed at the end of the Early Carboniferous, the melange and island arc as well as other tectonic units in the West Junggar were stitched together by the Late Carboniferous–Permian post-collisional granitoids.

In Northeast China, large volumes of Mesozoic–Cenozoic igneous rocks have developed as a result of long-lasting subduction of the palaeo-Pacific and Pacific plates beneath the eastern Eurasian continent. Previous studies have convincingly confirmed the presence of depleted mantle (DM), FOcal ZOne (FOZO) mantle and enriched mantle 1 (EM1) end-members; the enriched mantle 2 (EM2) end-member is probably present but it has been poorly constrained. The Late Cretaceous Shuangyashan suite, comprising a monzogabbro and diorite–porphyrite stocks and their cumulate hornblendite enclaves, from the Shuangyashan coal basin, Northeast China, is characterized by high initial87Sr/86Sr (0.70922–0.71095) and low initial143Nd/144Nd ratios (0.51221–0.51238) at 98 Ma. Their occurrence demonstrates that EM2 is present in the lithospheric mantle of Northeast China and its formation may be related to recycled continental material in a subduction setting.

Hollow carbon hemispheres (HCHs) were synthesized at 500 oC in the magnesium carbonate-metallic Li system with the help of CHBr3. The product was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM). XRD and electron diffraction (ED) pattern results showed that HCHs were graphite phase and polycrystalline. By FESEM and TEM observation, the diameters of the HCHs were in the range of 200-900 nm. The shell of the HCHs was single-layer and their thickness was about 31 nm. The formation mechanism of HCHs with the help of CHBr3 was discussed. Besides, the effect of reaction temperature and dosage of CHBr3 on the morphology of HCHs was studied.

A study was made of magnetic field effects (MFEs) on the photoreduction reaction of 2-methyl-1, 4-naphthoquinone (MNQ) in Brij 35 micellar solution containing 4-lauroylamino-TEMPO (2,2,6,6-tetramethylpiperidine-l-oxyl) radical (L-R) under magnetic fields below 1.75 T by a nanosecond laser flash photolysis technique. The triplet MNQ mainly underwent the hydrogen abstraction from Brij 35 molecule to give a radical pair. The escaped radical yield increased with magnetic fields from 0 to 0.62 T and then saturated from 0.62 to 1.75 T. MFEs for both system can be explained by the relaxation mechanism. However, it was supposed that additional radical, L-R affected the MFEs mainly through enhancing the spin-spin interactions of radical pairs. The effect of the micelle size on MFEs of the studying system was also discussed.

North Xinjiang, Northwest China, is made up of several Paleozoic orogens. From north to south these are the Chinese Altai, Junggar, and Tian Shan. It is characterized by widespread development of Late Carboniferous–Permian granitoids, which are commonly accepted as the products of post-collisional magmatism. Except for the Chinese Altai, East Junggar, and Tian Shan, little is known about the Devonian and older granitoids in the West Junggar, leading to an incomplete understanding of its Paleozoic tectonic history. New SHRIMP and LA-ICP-MS zircon U–Pb ages were determined for seventeen plutons in northern West Junggar and these ages confirm the presence of Late Silurian–Early Devonian plutons in the West Junggar. New age data, combined with those available from the literature, help us distinguish three groups of plutons in northern West Junggar. The first is represented by Late Silurian–Early Devonian (ca. 422 to 405 Ma) plutons in the EW-striking Xiemisitai and Saier Mountains, including A-type granite with aegirine–augite and arfvedsonite, and associated diorite, K-feldspar granite, and subvolcanic rocks. The second is composed of the Early Carboniferous (ca. 346 to 321 Ma) granodiorite, diorite, and monzonitic and K-feldspar granites, which mainly occur in the EW-extending Tarbgatay and Saur (also spelled as Sawuer in Chinese) Mountains. The third is mainly characterized by the latest Late Carboniferous–Middle Permian (ca. 304 to 263 Ma) granitoids in the Wuerkashier, Tarbgatay, and Saur Mountains. As a whole, the three epochs of plutons in northern West Junggar have different implications for tectonic evolution. The volcano-sedimentary strata in the Xiemisitai and Saier Mountains may not be Middle and Late Devonian as suggested previously because they are crosscut by the Late Silurian–Early Devonian plutons. Therefore, they are probably the eastern extension of the Early Paleozoic Boshchekul–Chingiz volcanic arc of East Kazakhstan in China. It is uncertain at present if these plutons might have been generated in either a subduction or post-collisional setting. The early Carboniferous plutons in the Tarbgatay and Saur Mountains may be part of the Late Paleozoic Zharma–Saur volcanic arc of the Kazakhstan block. They occur along the active margin of the Kazakhstan block, and their generation may be related to southward subduction of the Irtysh–Zaysan Ocean between Kazakhstan in the south and Altai in the north. The latest Late Carboniferous–Middle Permian plutons occur in the Zharma–Saur volcanic arc, Hebukesaier Depression, and the West Junggar accretionary complexes and significantly postdate the closure of the Irtysh–Zaysan Ocean in the Late Carboniferous because they are concurrent with the stitching plutons crosscutting the Irtysh–Zaysan suture zone. Hence the latest Late Carboniferous–Middle Permian plutons were generated in a post-collisional setting. The oldest stitching plutons in the Irtysh–Zaysan suture zone are coeval with those in northern West Junggar, together they place an upper age bound for the final amalgamation of the Altai and Kazakhstan blocks to be earlier than 307 Ma (before the Kaslmovian stage, Late Carboniferous). This is nearly coincident with widespread post-collisional granitoid plutons in North Xinjiang.

The Central Asian orogenic belt is the largest tectonic assembly of continental and oceanic terranes on Earth due to closure of the paleo–Asian Ocean in the Phanerozoic. Among major suture zones in the North Xinjiang region of western China, the North Tian Shan suture zone, because of collision between the Yili terrane in the south and the Junggar terrane in the north, contains the youngest ophiolitic rocks and may represent the terminal stage of development of the Central Asian orogenic belt in western China, but the timing of the suture zone remains poorly constrained. A sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb age of 316 ± 3 Ma (i.e., the beginning of the late Carboniferous) from the undeformed Sikeshu pluton, which crosscuts the suture zone, places a crucial upperage bound for the time of collision between the Yili and Junggar terranes. This event occurred later than, or nearly concurrent with, other accretion-collision events in the North Xinjiang region, implying that fi nal terrane amalgamation was completed in the late Carboniferous. The Sikeshu pluton shares geochemical characteristics of the widespread late Carboniferous to Permian postcollisional A-type and I-type granitoids with depleted-mantle–like Sr-Nd isotopic signatures in the North Xinjiang region. They all occurred during a protracted (ca. 320–270 Ma) episode of postcollisional magmatism that may have been induced by basaltic under plating due to either slab breakoff or delamination of thickened mantle lithosphere beneath the Central Asian orogenic belt. The same postcollisional magmatism also generated Cu-Ni-sulfi de– bearing, mafi c-ultramafi c magmatic complexes, adakites, and porphyry-type coppermolybdenum–bearing magmatic rocks in the North Xinjiang region.

Mn2+-doped ZnSe ethylenediamine-intercalated precursor nanoribbon bundles (MnxZn1?xSe?en3, en=ethylenediamine) were prepared through an improved solvothermal route, which is time-saving and more efficient compared with the traditional route. XPS, TGA, and FESEM were used to characterize morphology and composites of the precursor and it was proved that the doping process was successful. Electron paramagnetic resonance and photoluminescence (PL) spectra were used in a detailed experiment to characterize and study the Mn2+ doping state and Mn2+-Mn2+ interaction in MnxZn1?xSe?en3. Six well-resolved hyperfine lines, which are attributed to the Mn2+ allowed transition imply that the Mn ions were embedded inside MnxZn1?xSe?en3 lattices and partly replaced Zn. As shown in PL spectrum; the introduction of Mn2+ strongly increases the intensity of the PL peak. The internal Mn transition (4T1?6A1), which strongly increases the peak intensity depends on the average number of Mn atoms in the nanoparticals. As the Mn-doped concentration increases, the PL peak intensity is enhanced. A series of samples with different Mn-doping concentrations were prepared and studied. Combining the EPR results with PL spectra of the samples prepared, it is believed that under conditions of heating 40 h at 180 ?C and controlling Mn2+ ion concentration percentage at 2%-3% (x=0.02-0.03) in the compounds, the best doping can be achieved.

Dynamic spin chemistry, including magnetic field effects (MFE), magnetic isotope effects (MIE), CIDEP and CIDNP, has become a research area. In the present paper, the authors briefly introduced the development history and the spectroscopic research state of magnetic field effects for the radical reactions induced by laser excitation. The possible reasons for magnetic field effects of the radical reactions, theories for the conversion of singlet and triplet states, and mechanisms of magnetic field effects were explained and the recent development state of magnetic field effects for the radical reactions was also introduced to domestic scientists.

The most attractive form of future network content will be multimedia. When voice information is included, it usually carries core concepts for the content. Thus, a spoken document associated with multimedia content can very possibly serve as the key for indexing/browsing and retrieval. However, unlike written documents, multimedia or voice information is very often just audio/video signals. They are very difficult to index, browse or retrieve, since users cannot go through each of them from the beginning to the end during browsing. A possible approach may be to segment the audio/video signals automatically into short paragraphs, each with a central concept or topic, and then automatically generate a title and/or a summary for each of these, in either speech or text form. The topics and central concepts described in the segmented short paragraphs may then be further analyzed and organized into graphic structures describing the relationships among these topics and central concepts. Hence, the multimedia content can be automatically indexed much more efficiently and browsed and retrieved by the user based on the title, summary and graphic structure. We refer to this as the understanding and organization of spoken documents. An initial prototype system for such functions, with broadcast news taken as the example multimedia content, is presented. The graphic structure used to describe the relationships among the topics and central concepts are 2-dimensional tree structures developed based on probabilistic latent semantic analysis.

VRML (Virtual Reality Modeling Language) is used to model the 3D object of the Web page, and become as a standard for 3D information of World Wide Web. We propose a content-based VRML 3D object retrieval system. The system can display 3D objects queries to Web browsers interactively. User may give a VRML object, and find VRML scenes that use the similar object via user interface. In this system, we propose the automatic indexing scheme of VRML database according to our Oct-tree representation method, which could filter the VRML object efficiently. Our experience shows that the system is able to retrieve 3D objects from VRML scenes satisfyingly by the proposed approaches.

Because of the interest of 3D images and the popularity of World Wide Web, the number of 3D scene/objects and model database throughout the world is growing both in number and in size. VRML (Virtual Reality Modeling Language) is used to model the 3D object of the Web page, and become as a standard for 3D information. Most content-based retrieval (CBR) techniques such as shape and color comparison among objects are for image and video. The mechanisms are designed based on 2D information. In this paper, we propose a new similarity method, based on 3D information extracted from a VRML object database. The system includes multiple subsystems, which are conducted in two main parts. The first part includes the VRML object parser system and the normalization system. The second part includes the comparison system, database management system and a friendly graphical user interface. The method is the first step of our project, which aims to incorporate feature extraction of virtual reality objects, such as chairs, car, and others in 3D space. House interior designers can use the proposed system. The user can select proper scenes and furniture in order to meet the requirement of potential customers.