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The North China Craton (NCC) is widely regarded to have experienced considerable lithospheric thinning during the late Mesozoic. However, how the lower crust responded to the lithospheric thinning remains a topic of debate. Here we report zircon U-Pb-Hf isotopes, whole-rock geochemistry and Nd-Pb isotopic compositions for the Tianmushan pluton in Xinyang (Henan Province) from the central southern part of the craton. Zircon U-Pb dating of three texturally distinguishable phases from this pluton yield concordant ages of 122.4 ± 1.3 Ma for porphyritic monzogranite, 123.1 ± 1.1 Ma and 122.8 ± 0.9 Ma for medium-fine grained monzogranites, and 120.3 ± 1.4 Ma for fine-grained syenogranite. All the studied rocks have high SiO 2 (74.56–77.80 wt%) and total alkali (K 2 O + Na 2 O = 8.11–9.10 wt%), and low Al 2 O 3 (12.0–13.4 wt%), Fe 2 O 3 T (0.24–2.86 wt%) and MgO (0.09–0.26 wt%) contents with weakly peraluminous characteristic (A/CNK = 1.02–1.13). Meanwhile, they contain abundance in Ga, Rb, Nb, Y, Pb, Th, U and heavy rare earth elements (HREEs) with high 104Ga/Al and Nb/Y ratios. These geochemical features, combined with mineral morphology evidence, suggest that the Tianmushan pluton is intrinsically A 1 -type granite, formed in an intraplate extensional environment. The depletion in Ba, Sr, P, Eu and Ti and the "seagull" REE pattern might be attributed to extensive fractionation of plagioclase, K-feldspar, biotite, magnetite, apatite and monazite in the shallow crust. Furthermore, the granites show negative whole-rock ε Nd (t) values (−10.8 to −10.1), zircon ε Hf (t) values (−12.8 to −5.2), and relatively high initial Pb isotopes with (206Pb/204Pb) i ratios of 17.2833–17.6280, (207Pb/204Pb) i of 15.4774–15.5103 and (208Pb/204Pb) i of 38.1792–38.3587, respectively. They are comparable to the mafic granulitic xenoliths but different from those of the southern basement rocks in the craton (such as the Taihua and Xiong'er Groups), suggesting that the mafic granulitic lower crust could be the potential source for the Tianmushan granites. Together with the lithologic architecture and seismic profile of the deep crust beneath the Xinyang area, we proposed that the lower crust beneath the central southern part of North China had been further reworked and thinned in an extensional intracontinental environment after delamination in the Early Cretaceous. Moreover, the widespread occurrence of coeval A-type granitoids (130–110 Ma) in the whole eastern NCC indicates that the Early Cretaceous was a significant period of crustal extension and melting, which probably represent the peak of lithospheric thinning and cratonic destruction. • High-silica A-type granites formed between ca.123–120 Ma. • The granites were formed by melting of mafic granulitic lower crust. • The mafic lower crust was reworked and thinned in early Cretaceous. [ABSTRACT FROM AUTHOR]

Abstract: Recently there have been reports of forest regrowth occurring in different regions across the world. There is also a growing recognition of the potential beneficial impact that secondary forests may have on the global environment: providing crucial ecosystem services such as soil conservation, stabilization of hydrological cycles, carbon sequestration, and support for forest dependent communities. Consequently, there is a growing awareness of the need to recognize that landscapes are complex shifting mosaics wherein forest clearing and reforestation take place. In this study, the rates of reforestation, deforestation, forest regrowth and degradation were measured using multi-temporal Landsat images of Danjiangkou, China. Landsat data from 1990, 1999 and 2007 were (1) classified as dense forest, open forest and non-forest areas and (2) compared between years to identify forest cutting, regeneration and degradation. The results showed that there was a net gain of 29,315ha of forest area (including dense and open forest) from 1990 to 2007, showing a clear trend of reforestation in the study area. Forest modification (degradation and regrowth) and change categories (deforestation and reforestation) occurred simultaneously during the observation time period. Socioeconomic data from public statistics and environmental attributes allowed the assessment of the socioeconomic factors and the environmental conditions that caused these changes using non-metric multidimensional scaling (NMDS). The research showed that the socioeconomic factors due to different policies were major driving forces of forest transition, whereas environmental attributes of the underlying landscape constrained forest cover changes. These findings have led to a better understanding of forest transition at a local scale in our study region. Comprehensive knowledge of these relationships may be useful to reconstruct past forest transitions and predict future changes, and may help to enhance sustainable management practices aimed at preserving essential ecological functions. [Copyright &y& Elsevier]

• Peraluminous granites in the southern NCC formed at ~ 1.86 Ga, ~1.90 Ga and ~ 1.96 Ga. • The Paleoproterozoic granitic magmatism was likely due to the collision between the Eastern and Western Blocks of the NCC. • The granites recorded heterogeneous Paleoproterozoic crust in the southern NCC. As one of the oldest cratons on Earth, the North China Craton (NCC) is a frequent area for geological research due to its complex crustal evolution. Regarding the Paleoproterozoic crustal evolution of the craton, most studies have focused on continental amalgamation (i.e. horizontal crustal evolution), but few on the vertical crustal evolution. Here we report whole-rock geochemistry, zircon U-Pb geochronology and Lu-Hf isotope geochemistry for the Xinyang granites to constraint the vertical crustal structure and evolution of the southern NCC. The studied granites comprise two-mica K-feldspar granite and garnet-bearing K-feldspar granite. All the rocks have high SiO 2 and total alkali, but low CaO, MgO and Fe 2 O 3 T contents. Their A/CNK values (1.05–1.28) suggest that they are peraluminous rocks. These granites are enriched in LILE (Rb, Th and K), depleted in Sr, P and HFSE (Nb and Ti). The two-mica K-feldspar granites show obviously fractionated REE patterns ((La/Yb) N = 18.3–387) with negative or positive Eu anomalies (δEu = 0.47–1.03, 4.85–6.72), while the garnet-bearing K-feldspar granites have flat REE patterns ((La/Yb) N = 1.69–4.89) with extraordinary negative Eu anomalies (δEu = 0.22–0.42). The magmatic zircons of the two-mica K-feldspar granites yield crystallization ages ranging from ~ 1.86 Ga to ~ 1.90 Ga, and those of the garnet-bearing K-feldspar granites give crystallization ages of ~ 1.90 Ga. Previous work also reported a biotite K-feldspar granite pluton formed at ~ 1.96 Ga in the Xinyang area. Taken together, three major episodes of Paleoproterozoic granitoid events (~1.86 Ga, ~1.90 Ga and ~ 1.96 Ga) are recognized in the area. Combined with regional geochronological investigations, the peraluminous granitic magmatic activities occurring during 1.96–1.86 Ga in the Xinyang area could be linked to the collision between the Eastern and Western Blocks of the NCC. Alternatively, zircon Hf isotopic compositions suggest that these rocks derived from partial melting of pre-existing crust with heterogeneous compositions. Zircons from the ~ 1.86 Ga two-mica K-feldspar granites yield ε Hf (t) values of −5.2–1.7 with T crust of 2.40–2.86 Ga, compared to zircons from the ~ 1.90 Ga two-mica K-feldspar granites which yield wide range of ε Hf (t) values of −13.5–1.0 with T crust of 2.50–3.42 Ga. In contrast, the ~ 1.90 Ga garnet-bearing K-feldspar granites have homogeneous negative zircon ε Hf (t) values ranging from −11.8 to −10.4, with T crust ranging from 3.23 to 3.30 Ga. Moreover, zircons from the biotite K-feldspar granites have ε Hf (t) values of −0.6–2.6, corresponding to T crust of 2.44–2.77 Ga. Based on abovementioned geochemical signals, we propose that the Paleoproterozoic crust in the southern NCC likely consisted of two parts in vertical, the upper Middle-Late Archean crust and the lower early Paleoproterozoic crust with Eo-Paleoarchean crustal remnants. During the Paleoproterozoic, the southern NCC experienced multi-stage crustal reworking, indicating that a stable continental crust likely had been formed by the end of Archean. [ABSTRACT FROM AUTHOR]

The stable chromium isotope composition of Earth's mantle has been suggested to be heterogeneous, with mantle-derived chromitites slightly enriched in heavier Cr isotopes than mantle-derived silicate rocks. To better understand such heterogeneity and to search for a potentially complementary light Cr isotope reservoir in the mantle, we analyzed the stable Cr isotope compositions (δ53Cr expressed as deviation of sample 53Cr/52Cr from NIST SRM 979) of whole-rock pyroxenite and peridotite xenoliths from the North China Craton using a double spike technique. The δ53Cr values of the peridotites vary from −0.21‰ to −0.07‰ with an average value of −0.14 ± 0.10‰ (2SD, N = 5), which overlaps with the range of the Bulk Silicate Earth (−0.12 ± 0.10‰). In contrast, pyroxenites in this study yield lower δ53Cr values (−0.30‰ to −0.14‰ with an average value of −0.21 ± 0.08‰, 2SD, N = 20). The variation in the δ53Cr values of the pyroxenites can be explained by a Rayleigh distillation model during partial melting of the primitive mantle. The model provides minimum Cr isotope fractionation factors during partial melting ranging from 0.01‰ to 0.12‰, with light isotopes enriched in the melt. Combined with literature data, our results suggest that both peridotites and basalts are indistinguishable from the Bulk Silicate Earth in terms of δ53Cr. However, pyroxenites and chromitites are isotopically lighter and heavier than the Bulk Silicate Earth, respectively. Future work is needed to investigate the petrogenetic relationship between chromitites and pyroxenites in order to understand why they seem to complement each other in δ53Cr. [ABSTRACT FROM AUTHOR]

Abstract: The complexity of the relationship between suspended sediment concentration (SSC) and river discharge (Q) remains a challenge for SSC prediction in hyperconcentrated rivers. In this study, the wavelet-artificial neural network model (WANN) was built to predict SSC in the Kuye River, a representative hyperconcentrated river in the middle Yellow River catchments of China. In the WANN model, the observed daily time series for Q and SSC of 2193days (from 1967 to 1972) were decomposed into subseries at different scales using discrete wavelet analysis. Then, the effective subseries were selected to construct Q/SSC inputs to the feed-forward back-propagation artificial neural network (BP ANN) to predict SSC 1day in advance (the time resolution of the observed data). The coefficient of determination (R 2) and root-mean square error (RMSE) were adopted to evaluate the model''s performance. The WANN model showed higher prediction accuracy (R 2 =0.846 and RMSE=29.82) than the sediment rating curve (SRC) model (R 2 =0.537 and RMSE=55.40) or the ANN model (R 2 =0.664 and RMSE=43.13). The WANN model exhibited more robust performance than the SRC and ANN models, indicated by the appropriate values of error autocorrelation and input-error correlation. Negative values of predicted SSC occurred in ANN and in WANN models. By adjusting the negative values to zero, the WANN R 2 was improved by 4.3% from 0.846 to 0.882. In general, the results illustrate that the WANN model better predicts SSC in a hyperconcentrated river setting, with highly nonlinear and nonstationary time series. [Copyright &y& Elsevier]

Abstract: This paper analyzes runoff and soil loss in relation to the rainfall regimes and land use changes in a small mountainous watershed in the Three Gorges Area (TGA) of China. Based on 10years of rainfall measurements and K-means clustering, 152 rainfall events were classified into three rainfall regimes. The mean statistical features of different rainfall regimes display a marked difference. Rainfall Regime I is events of medium amounts (31.8mm) and medium duration (1371min). Rainfall Regime II is events with high amounts (54.0mm), long duration (2548min), and an infrequent occurrence. Rainfall Regime III is events of low amount (22.2mm), short duration (494min) and high frequency. Each rainfall regime results in differing levels of runoff and erosion and Rainfall Regime I causes the greatest proportion of accumulated discharge (368.7mm) and soil loss (4283t). In the different rainfall regimes, the values of the mean runoff coefficient and the mean sediment load were ordered as follows: Rainfall Regime II>Rainfall Regime I>Rainfall Regime III. These results suggest that greater attention should be paid to Rainfall Regimes I and II because they had the most erosive effect. In the Wangjiaqiao watershed, the changes in land use primarily affected the paddy fields, where the cropland decreased significantly and the forest and orchards increased by 9.9% and 7.7%, respectively, during 1995–2004. The ANOVA shows land use changes caused significant decreasing trends in the runoff coefficients (P<0.01) and sediment loads (P<0.01). In order, the most sensitive response of runoff and erosion to land use was Rainfall Regime II>Rainfall Regime>Rainfall Regime III. Rainfall characteristics are decisive for the relative importance of different storm runoff generation mechanisms. The land use changes in the study watershed have considerably decreased runoff and soil loss. [Copyright &y& Elsevier]