Two Types of Granites in the Western Yangtze Block and Their Implications for Regional Tectonic Evolution： Constraints from Geochemistry and Isotopic Data

In the western Yangtze Block, widespread Mesoproterozoic to Neoproterozoic rocks are the key to understanding the Precambrian tectonic-magmatic evolution of the region. However, their petrogenesis and tectonic setting are still controversial. In this paper, zircon U-Pb ages, Sm-Nd isotopic and whole-rock geochemical data are reported from selected fresh samples in the southern Dechang county, southwestern China, in order to constrain their emplacement age and magma source, as well as their petrogenesis and tectonic setting. They are mainly composed of biotite monzogranite, monzonitic granite, biotite granodiorites, and quartz diorite. Two ages of 1055 ± 43 Ma and 837.6 ± 3.8 Ma were obtained through zircon U-Pb dating by LA-ICP-MS and LA-MC-ICP-MS, respectively. According to their major element compositions, the Grenville-age granites are peraluminous calc-alkaline series calcic S-type granite. In contrast, the mid-Neoproterozoic granites are metaluminous calc-aikaline series alkalic I-type granite. Furthermore, the S-type granites are enriched in LREEs relative to HREEs with （La/Yb）N ratios of 3.85-18.56 and underwent major fractionation with strongly negative Eu anomalies （Eu/Eu＊ = 0.38-0.66）. In the MORB-normalized trace element variation diagram, all the samples are enriched in Ce and large ion lithophile elements such as Rb, Th, and K, and depleted in high field strength elements such as Nb, and Ti, with negative Sr and Ti anomalies. The I-type granites are enriched in LREEs with slight negative Eu anomalies （Eu/Eu＊= 0.83-0.93）. They are characterized by the enrichment of highly incompatible elements （such as K, Rb, Ba, Th） and LREEs, relative to MORB. Neodymium isotopic data show that the S-type granites display 143Nd/144Nd values of 0.51241-0.51256, and have eNa （t = 1055 Ma） values of （-3.29） to （-3.81）. Calculated tDM ages yield values from 1.87 to 1.91 Ga with the tDM.2stg ages of 1.86 to 1.9 Ga. The I-type granites have 143Nd/144Nd ratios between 0.51192 and 0.51195, corresponding to initial eNd （t = 837 Ma） values of 1.22 to 5.63. Calculated tDM ages yield values from 1.0 to 1.38 Ga and the tDM.2stg ages yield values from 0.99 to 1.06 Ga. The S-type granites are distinguished as syn-collision granite, whereas the I-type granites were formed as arc magmas according to the Rb-（Yb＋Ta） and R1-R2 tectonic discrimination diagrams. To conclude, there are two types of spatially associated granite, the Mesoproterozoic S-type granite which were derived from re- melting of upper crustal mudstone and/or clastics and resulted from the convergence of two continental plates, and the mid-Neoproterozoic I-type granite which formed in continental arc and resulted from mantle-derived magma mixed crust material, in the western Yangtze Block. Furthermore, we suggest that collision between the Yangtze and Cathaysia blocks occurred at about 1055 Ma, and caused the S- type granite. The I-type granite related to the subduction of oceanic lithosphere eastward underneath the Yangtze Block in the mid-Neoproterozoic.

Newly Discovered Fluvial-Lacustrine Sediments in the Western Yangtze Block and their Geological Significance for the Emeishan Large Igneous Province

Objective The Emeishan large igneous province （ELIP） in SW China is the only one large igneous province in China recognized by international geologists. Previous studies of ELIP over past two decades indicate that the ELIP age, duration, scale and generation mechanism are still controversial. Among those scientific topics, some scholars suggest that ELIP is an example of up-doming prior to LIP formation, which was evidenced by： （1） The thickness of the Yangxin Formation （P^v） limestone unit, which lies directly beneath ELIP, reduces from the center of erosional area to the outer edge. （2） Paleo-karst surfaces are present. （3） The clastic rocks of alluvial fan deposits, from the eroded materials in the maximum uplifted area, developed surrounding the inner zone. However, other scholars urge that those so-called ＂alluvial fan＂ deposits are ＂hydromagmatic deposits＂, erupted or emplaced at or near sea level, and conclude that there was no pre-emptive uplift in ELIP. In order to constrain the above-mentioned scientific issue, we conducted detailed field geological investigations and systematically measured geological sections to provide new evidence by using sedimentary data.

Effect of vacuum level on microstructure and mechanical properties of titanium-steel vacuum roll clad plates

Vacuum roll cladding （VRC） was used to bond pure titanium （Ti） plate to a plain low carbon steel （Q345） with the aim of obtaining a high-quality Ti-steel clad plate. The effect of interfacial compound on the mierostructure and mechanical properties of Ti-steel clad plate was studied by electron probe microanalysis, scanning electron microscopy, X-ray diffraction and shear test. The clad plates were heated at 850 ℃ for 120 min and welded at different levels of vacuum. The results indicated that the cracked zone of the bonded interface decreased significantly with the increase in the level of vacuum during welding. Welding at atmospheric pressure, the randomly distributed TiN damaged the continuity of TiC and the uniformly diffused region of Ti and Fe at the bonded interface, while welding in vacuum of 1 × 10^-2 Pa, maximum shear strength of 298 MPa was obtained because of the decrease in TiN content.

Hot Deformation Behavior and Microstructural Characteristics of Ti–46Al–8Nb Alloy

Hot deformation behavior, microstructural evolution and flow softening mechanism were investigated in Ti-46A1-8Nb alloy via isothermal compression approach. The true stress-strain curves exhibited typical work hardening and flow softening, in which the dependence of the peak stress on temperature and strain rate was obtained by hyperbolic sine equation with Zener-Hollomon （Z） parameter, and the activation energy was calculated to be 446.9 kJ/mol. The microstructural analysis shows that the alternate dark and light deformed ribbons of Al-rich and Nb-rich regions appeared and were associated with local flow involving solute segregation. The Al segregation promoted flow softening mainly arising from the recrystaUization of V phase with low stacking fault energy. The coarse recrystallized 7 and several massive phase were observed at grain boundaries. While in the case of Nb segregation, t/B2 phase harmonized bending of lamellae, combined with the growth of recrystallized γ grains and α ＋ β ＋ γ→α＋ γ transition under conditions of temperature and stress, leading to the breakdown of α2/γ lamellar colony. During the hot compression process, gliding and dissociation of dislocations occurred in γ phase that acted as the main softening mechanism, leading to extensive γ twins and cross twins in α/γ lamellae and at grain boundaries. In general, homogeneous microstructure during the hot defor- mation process can be obtained in TiAl alloy with high Nb addition and low Al segregation. The deformation substructures intrinsically promote the formability of Ti--46Al-8Nb alloy.

Microstructures and Hardness Properties for β-Phase Ti-24Nb-4Zr-7.9Sn Alloy Fabricated by Electron Beam Melting

Atomized, pre-alloyed Ti-24Nb-4Zr-7.9Sn （wt%） powder was used to fabricate solid, prototype components by electron beam melting （EBM）. Vickers microindentation hardness values were observed to average 2 GPa for the precursor powder and 2.5 GPa for the solid, EBM-fabricated products. The powder and solid product microstructures were examined by optical and electron microscopy. X-ray diffraction analyses showed that they had bcc β-phase microstructure. However, it was found by transmission electron microscopy that the EBM-fabricated product had plate morphology with space -100-200 nm. Although the corresponding selected area diffraction patterns can be indexed by β-phase plus α＂-martensite with orthorhombic crystal structure, the dark-field analyses failed to observe the α＂-martensite. Such phenomenon was also found in deformed gum metals and explained by stress-induced diffusion scattering due to phonon softening.

KINETICS OF ION TRANSFER ACROSS LIQUID/LIQUID INTERFACE BY CHRONOPOTENTIOMETRY WITH LINEAR CURRENT SCANNING

The equation of the potential-current curve for the ion transfer across the liquid/liquid interface during the linear current scanning has been derived theoretically. A method to calculate the kinetics parameters for the ion transfer by the way of linear current scanning is presented. The transfer of TPAs^+ ions, which is a typical basic electrolyte ion usually used in liquld/liquid interface electrochemistry, was practically investigated at the water/nitrobenzene interface.

From Tongbo Village to Widow Villagc The Legacy of the Chinese Civil War

Located on Dongshan Island, off the coast of Fujian province, is a typical rural village called Tongbo. On May 10, 1950, 147 men were abducted by the KMT army on its way to Taiwan. Since a majority of the men were already married, overnight, their wives became ＂widows,＂ and most would remain so for the rest of their lives. Consequently, Tongbo village became more widely known as Widow Village. The first objective of this paper is to document the tragic experiences of men and women in Tongbo village, focusing on these forced separations in 1950, the possibility of reunion after 1987, and the struggle to cope with the difficulties in between. The second objective of this paper is to argue that while heartbreaking, the experiences of this village are not extraordinary in the context of the Chinese Civil War. What made the men and women in Tongbo extraordinary is not their collective suffering, but how these villagers suffered less, not more, than in many other places, because of the actions of three key figures.

Entrepreneurship and Unemployment Cycles： A Delay Differential Equation Approach

This paper is an application of delay differential equations to entrepreneurship and unemployment. It shows that the results of empirical studies can be replicated through a simple DDE. The paper also carries out a comparative study between a solution of a DDE and the observation of cyclic behaviors. The calculated delay （and growth rate） of the entrepreneurship DDE for the US and Spain is 1.25 years （1.25）, for Ireland is 1.75 years （0.89）, and for the UK is 2 years （0.78）. The delay （and growth rate） of the unemployment DDE for the US and Ireland is 1.5 years （1.04）, for Spain is 2 years （0.78）, and for the UK is 2.5 years （0.62）.