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Thermal analysis is widely used for the measurement of the relationship between temperature and physical properties of the materials. Many studies have reported different thermal analysis methods, including thermogravimetry (TG), derivative thermogravimetry (DTG), differential heat analysis (DTA), and differential scanning calorimetry (DSC), but few comprehensively studied the factors influencing TG-DTA by the combined thermogravimetry–differential thermal methods. In this study, taking chalcanthite as the research object, the thermogravimetric–differential thermal analyses were systematically conducted by using synchronous thermal analyzer technology. The results demonstrate that 1) DTA curves of low- and medium-weight chalcanthite show five dehydration endothermic peaks, while TG curves do not display obvious weight-loss steps; DTA and TG curves of high-weight chalcanthite samples, on the other hand, illustrate three endothermic peaks, indicating three-step loss of crystalline water; 2) higher weight of samples may cause longer time of internal heat transfer and larger temperature gradient, consequently resulting in the expansion of DTA peak shape and the decline of resolution as well as the increase of the peak temperature; 3) the weight-loss deviation between the measured and theoretical data is relatively higher in the low-weight samples than that in the medium- and high-weight samples; 4) the heating rate can increase the DTA curve peak and thermal inertia and the temperature at the thermodynamic equilibrium, causing the temperature lagging behind and the overall peak moving toward high temperature; 5) sample grinding may destroy the structure of the crystal, thereby breaking the relatively weak chemical bond, and thus affects the structure of thermogravimetric–differential thermal analyses. These suggest that the sample weight, heating rate, and sample grinding probably have significant effects on the thermogravimetric–differential thermal analyses. Therefore, proper experimental conditions are needed to obtain the accurate results during the thermogravimetric–differential thermal analyses. This study can provide a basis and reference for future synchronous thermal analyses.

The petrogenesis of A-type granites with different occurrences in the Nanling Range remains unclear. In this study, a case study of the Jiuyishan complex massif and Xianghualing intrusive stocks was conducted to determine this problem. The Jiuyishan complex massif is composed of four units (Jinjiling, Pangxiemu, Shaziling and Xishan). These four units have similar zircon U-Pb ages of approximately 153 Ma, with high Zr + Nb + Ce + Y contents (>350 ppm), high 10,000 Ga/Al ratios (>2.6), and a high crystallization temperature, indicating A-type affinities. They show a gradual change in lithology and geochemistry, implying a fractional crystallization process. These units also have similar εNd(t) values (−8.2 to −5.8) and zircon εHf(t) values (−7.5 to −2.2) except for the Shaziling MMEs (mafic microgranular enclaves) (−14.2 to 4.8), demonstrating their lower crustal source. However, the Shaziling unit may have contributed mantle-derived magma based on the geochemical data of its hosted MMEs. In comparison, the two Xianghualing intrusive stocks have similar geochemical features but exhibit highly evolved features (high Rb, U, Y, Ta and Nb contents and low Eu, Ba, Sr, P, Ti, Ca, Mg and Fe contents, with V-shaped REE distribution patterns). They have different zircon U-Pb ages of approximately 160 Ma and 155 Ma. The two stocks also have similar whole-rock εNd(t) values (−6.5 to −5.7) and zircon εHf(t) values (−7.6 to −2.7) and equally illustrate a lower crustal source region. Combining with their vertical zonation, they may have experienced remarkable fractional crystallization with possible assimilation processes. We propose that the Jiuyishan complex and Xianghualing stocks have two distinct fractional crystallization mechanisms during their formation. The Jiuyishan complex was formed by in situ crystal mush fractionation, while the Xianghualing stocks were formed by flowage differentiation during magma ascent or gravitational settling during magma solidification after emplacement. However, more than one mechanism affected the fractional crystallization processes of these granitic rocks. [ABSTRACT FROM AUTHOR]

Hulun Buir, Inner Mongolia, is located at the northeastern part of the North China Craton, with a large area of Mesozoic granites. These granites are of great significance for studying the evolution, tectonic environment and dynamic mechanism of the lithosphere beneath the North China Craton. However, few have been studied on the genesis, tectonic setting and emplacement mechanisms of the monzonitic granites from the Hulun Buir. In this paper, based on field geological survey, systematic studies have been carried out on early Mesozoic granite from the Hulun Buir in terms of major and trace element compositions as well as zircon U-Pb isotope dating. Zircon U-Pb isotope dating shows that these granites were the product of magmatic activity in the Early Triassic ((251. 1±1. 2)Ma)and Early Jurassic((187. 4±1. 1)Ma). Early Triassic and Jurassic granites belong to high-K calc-alkaline types. These granites are rich in high rare earth elements (LREEs) and large ion lithophile elements (e. g., Rb, Th, U, K), but relatively deputed in high field strength elements( HFSEs) such as Nb, Zr, Hf, P, Ti, which are similar to the average distribution pattern of Chinese monzonitic granite. The incorporated results of the trace element characteristics and the geological research studies show that the Hulun Buir Mesozoic granites were formed in the crystallization differentiation of crust-derived magma. Early Triassic granite intrusive rocks were formed in intraplate extensional environments; the tectonic setting of early Jurassic granite formation was related to the interaction between continental crusts and the subduction of the oceanic crust (i. e., Paleo-Asian Ocean) towards the continental crust (i. e. Siberian plate) i e. the oceanic subduction-collision environment, and the subduction was mixed with a certain amount of oceanic crust components. The occurrence of the high-potassium granite also suggested the subduction and collision of the oceanic crust of the Eurasian Ocean in implying that the Early Mesozoic intrusive rocks were probably formed in the orogenic belt(island arc and active continental margin). This study can provide an important geological basis for non-ferrous metal prospecting in the Hulun Buir [ABSTRACT FROM AUTHOR]

The lithospheric mantle beneath the South China Block (SCB) underwent a dramatic transformation from depleted to enriched during late Mesozoic. With a view to deeply understand this process, here we investigate the Mesozoic basalts and their melt inclusions from the Daoxian and Ningyuan regions within the central SCB. The geochemical features of the melt inclusions in these basalts suggest that these rocks originated from the lithospheric mantle enriched through interaction with K-rich aqueous fluids released from subducted Palaeo-Pacific oceanic sediments, whereas the Ningyuan basalts were mainly derived from the asthenospheric mantle source. Geochemical modelling indicates that the Daoxian basalts were generated from 15%-25% of partial melting of garnet lherzolite, whereas the Ningyuan basalts originated from 10%-20% of partial melting of garnet pyroxenites. Our data, combined with those from other Jurassic basalts suggest a temporal evolution of the SCB mantle sources during the Late Mesozoic. Diverse crust–mantle interactions through mixing of the asthenospheric melts with variable proportions of subducted Palaeo-Pacific oceanic sediments might account for the spatial heterogeneity of mantle sources observed beneath the SCB. The transition from Tethyan tectonic realm to the Palaeo-Pacific tectonic regime might have played a significant role in the transformation of the lithospheric mantle beneath the SCB. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a general thermodynamically-based model is presented for the solubility of H2O–CO2 in silicate melts over a wide range of temperatures (from 933K to 2003K), pressures (up to 30kbar) and melt compositions (from ultramafic to silicic, from metaluminous to peraluminous, and from subalkaline to peralkaline). Using an equation of state for the fluid phase that differs from previous models and deriving activity coefficients of species in silicate melts based on a specific interaction theory, this model can not only reproduce the data used for calibrations, but also predict the solubility well beyond the data range. The accuracies of solubilities predicted from this model are shown to be 7.2% for H2O and 9.7% for CO2, respectively, which are well within the experimental uncertainty. In addition, this model can be applied to the determination of equilibrium saturation pressure at which silicate melts are saturated with a fluid phase, modeling the evolution of ascending magmas through degassing processes, and elucidating the fluid-melt partitioning behavior of CO2 and H2O. An online version of this model is available at the website: http://calc.geochem-model.org/Test/Services/WebForm1.aspx and the program can be downloaded at: www.geochem-model.org/archives/programs.htm. [Copyright &y& Elsevier]