Diffusion of aluminum in MgO: A thermodynamic approach study

We have applied a thermodynamical model to calculate the diffusion coefficient of aluminum in MgO with the aid of bulk elastic properties. Our calculated diffusivities as a function of temperature and pressure are compared with the existing results derived from experimental or theoretical investigations. We find that the present model provides a satisfactory estimation for the activation volume and the activation enthalpy.

Origin of the Earth:A proposal of new model called ABEL

The Earth was born as a dry planet without atmosphere and ocean components at 4.56 Ga,with subsequent secondary accretion of bio-elements,such as carbon（C）,hydrogen（H）,oxygen（O）,and nitrogen（N） which peaked at 4.37-4.20 Ga.This two-step formation model of the Earth we refer to as the advent of bio-elements model（ABEL Model） and the event of the advent of bio-elements（water component） as ABEL Bombardment.It is clear that the solid Earth originated from enstatite chondrite-like dry material based on the similarity in oxygen isotopic composition and among other isotopes.On the other hand,Earth＇s water derives primarily from carbonaceous chondrite material based on the hydrogen isotopic ratio.We present our ABEL model to explain this enigma between solid Earth and water,as well as secondary accretion of oxidizing bio-elements,which became a precursor to initiate metabolism to emerge life on a highly reductive planet.If ABEL Bombardment had not occurred,life never would have emerged on the Earth.Therefore,ABEL Bombardment is one of the most important events for this planet to evolve into a habitable planet.The chronology of ABEL Bombardment is informed through previous researches of the late heavy bombardment and the late veneer model.ABEL Bombardment is considered to have occurred during 4.37-4.20 Ga,which is the concept to redefine the standard late heavy bombardment and the late veneer models.Also,ABEL Bombardment is the trigger of the transition from stagnant lid tectonics to plate tectonics on this planet because of the injection of volatiles into the initial dry Earth.

Frontiers in early Earth history and primordial life--PartⅠ

The history of the early Earth is shrouded in mystery, and one of the major outcomes of the Apollo Program, lunar sampling, and the data acquired by subsequent orbiting missions, is that the Moon is an important analogue for the Hadean Earth, which includes primordial planet-forming materials. We assemble two special issues of ＂Geoscience Frontiers＂ with state-of-the-art contributions that provide insights into planetary formation, Earth＇s early history and primordial life. New theories show why the Earth began as a dry planetary system and was later seeded by an ocean-atmosphere system through the bombardment of carbonaceous chondrites. A combination of the information concerning the evolution of Earth, Mars, and the other terrestrial planets is important in understanding the fate of the primordial continental crustal materials and the making of habitable planets.

Zn-Rich Spinel in Association with Quartz in the Al-Rich Metapelites from the Mashan Khondalite Series, NE China

Al-rich metapelites from the Mashan khondalite series are characterized by the assem- blage Spl＋Grt＋Sil＋Crd＋Bt＋Pi （An72）＋Kfs＋Quartz＋graphite. Large amounts of spinel＋quartz assem- blages occur as inclusions in garnet and prismatic sillimanite in the Ai-rich metapelites of the Mashan complex, NE China. The chemical composition of spinel is characterized by Zn-rich （Xzn=0.33-0.40. Xzn=Zn/Zn＋Mg＋Fe＊） （Fe＊=FeZ＋＋Fe3＋） and Fe3＋ rich （up to 0.31 p.f.u.）. The characteristic chemical composition and the mineral association indicated that the formation of spinel and quartz assemblage may be due to the breakdown of Zn-rich staurolite. The geothermobarometers studies show that the peak temperature of the Mashan complex is around 820 ℃ and the peak pressures is 8.0 kbar. The Mashan complex shows a typical orogen style P-T path.

Kawai型多顶砧高压装置上0～8GPa静水压力下单晶金的超声波弹性测量

使用Kawai型多顶砧高压装置在0～8GPa静水压力下对单晶金进行了超声波弹性测量.测得的P-波速度值与Daniels等人的高压弹性数据非常吻合.金在常温常压下的3个独立的弹性常数为C11=192.7GPa,C12=162.9GPa和C44=42.4GPa.基于对超声波测量结果的分析,得出3个弹性常数的压力导数值为C11′=7.12,C12′=6.24,C44′=1.82.计算出的等温体弹性模量及其压力导数值为KT0=166.44GPa和KT0′=6.56,这表明在约23GPa和常温条件下作为压力尺度的Anderson等人的金的状态方程(KT0′=5.5)给出的压力值偏低约1.0GPa,金的状态方程应该重新进行修正.

Glass melt inclusion in clinopyroxene from Linqu Cenozoic basalt,Shandong Province,China

Cenozoic basalts from the Linqu County, Shandong Province, China entrain some clinopy- roxene crystals, of which many contain abundant glass melt inclusions. These melt inclusions are ex- tremely irregular in shape with most grain sizes in a range of 10-50 μm and coexist with low-Mg# olivines, labradorites and Ca-rich potassium feldspars. In-situ major and trace element analyses show that the glass melt inclusions are high in alkalis (Na2O+K2O > 10 wt%), SiO2 (>54 wt%), CaO and FeO (>4 wt%), but low in MgO (Mg# < 20), and have LREE enrich- ments ((Ce/Yb)cn = 11.6-16.4) and apparently posi- tive Eu anomalies (Eu/Eu* > 2), thus having phonoli- tic compositions. The compositional features of cli- nopyroxene crystals, glass melt inclusions and their coexistent minerals suggest that these melt inclu- sions were exotic melts in clinopyroxenes trapped prior to their entrainment in the host basalt. The dis- covery of these melt inclusions provides a new ap- proach to further investigating the evolution of Meso- zoic lithospheric mantle beneath the southeastern North China Craton.

Water solubility in orthopyroxene: Dependence on temperature and Al content

The water solubility in Al-Fe-Mg orthopyroxene[(Mg,Fe,Al)(Si,Al)O3:XFe=0.1]was investigated as a function of temperature and Al contents.Experiments were performed at 10 kbar with temperatures ranging from 800 to 1200°C under water-saturated conditions.Water contents in the(Mg,Fe)SiO3–H2O–Al2O3system were determined using unpolarized Fourier transform infrared spectroscopy.The present results show that water solubility in Al-bearing orthopyroxene decreases systematically with temperature from approximately 1 weight%at 800°C to 568±58 ppm at 1200°C and increase significantly with increasing Al2O3contents under the same annealing temperature and pressure.Combined with published results on the dependence of hydroxyl solubility on water fugacity and pressure,the present results can be described by the relation20.5OH H O()exp nC A T f1bar solid,R H V P T where A=0.0024±0.0015 ppm/bar0.5,1bar H=103.348±9.768 kJ/mol,andsolid V=9.2±1.1cm3/mol.This equation implies that the incorporation mechanism of water in aluminous orthopyroxene involves the isolated OH groups.Based on the experimentally established solubility model used in this study,it is suggested that water solubility decreases with increasing temperature under typical upper mantle pressure.The predicted temperature dependence of water solubility is in good agreement with the previous experimental observations in Al-bearing orthopyroxene,but the opposite dependence is observed in Al-free systems.Moreover,our estimation of the water solubility in upper-mantle minerals as a function of depth for a typical oceanic geotherm might be of potential importance in interpreting the geophysical observations.

Trace element composition in tuite decomposed from natural apatite in high-pressure and high-temperature experiments

Tuite has been suggested as a potential reservoir for trace elements in the deep mantle,but no evidence confirms this supposition.By using a natural apatite as starting material,the trace-element-bearing tuite large crystals were obtained under highpressure and high-temperature conditions(15 GPa and 1800 K).X-ray diffraction pattern and Micro-Raman spectrum of the run product confirm that tuite was synthesized.The concentrations of trace elements in tuite crystals were analyzed by laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS).The rare earth element patterns of tuite show enrichment of light rare earth elements relative to heavy rare earth elements.Tuite shows high concentrations of Th and Sr,and negative anomalies of Rb,Nb,and Hf.The results show that tuite can accommodate a large amount of trace elements.Tuite might be an important host to accommodate trace elements if there is much apatite subducted into the deep mantle.