地球材料物理性质和大陆深部构造意义

本文着重讨论：（１）当前大陆深部构造研究面临的困惑和挑战；（２）地球材料物理性质研究在深部构造中的意义；（３）对我国开展这个领域研究的希望和建议。文章强调地球材料物理性质不仅是深部构造研究的核心问题之一，同时也是地球物理成果合理解释的重要约束条件。

地幔转换带520km地震不连续面及其成因

前人研究表明410km和660km地震不连续面分别由橄榄石向瓦兹利石相变和后尖晶石相变引起。但对520km地震不连续面(简称D520)的研究相对较少,对其成因的解释还存在很大争议。橄榄石中瓦兹利石-林伍德石相变以及CaSiO3钙钛矿的出溶反应被广泛认为是D520的相变成因。辉石相变为尖晶石+斯石英组合也曾被认为是D520的可能成因。1 400℃条件下对MgSiO3辉石相变的实验研究,结合前人对橄榄石相变的研究成果,计算了方辉橄榄岩在1 400℃、18GPa条件下因辉石-瓦兹利石+斯石英和瓦兹利石-林伍德石相变引起的密度增量和波速增量,发现俯冲方辉橄榄岩中辉石的相变对520km深度的密度增量和波速增量有很大的贡献,有助于形成D520。此外,在探讨D520的成因时应综合考虑地幔转换带中温度,水以及矿物间Fe、Mg、Ca等主量元素分配等因素的影响。

Origin of Li-F-rich granite: Evidence from high P-T experiments

Though magmatic origin of Li-F-rich granite has been supported effectively by the existence of volcanic and subvolcanic rocks and melt inclusions trapped in them with similar chemical compositions, evidence from high T-P experiments is poor up to now. To simulate the evolution process of Li-F-rich granite and to interpret its forming mechanism, a series of melting-crystallization experiments were carried out. Under the conditions of 1×108 Pa and 570–700°C, a magmatic mineral association of quartz + alkali feldspar + lithium muscovite/ferromuscovite ± fluorite ± cassiterite is found in leucogranite-HF-H2O system. This indicates the following points: (i) Fluorite, light-colored muscovite and cassiterite can crystallize directly from the Li-F-rich granitic melt. (ii) The coexistence of dark-colored micas (e.g. biotite) and light-colored micas (e.g. lithium muscovite and ferromuscovite) suggests that the muscovite granite and two-mica granite can be formed under magmatic condition. The zonal texture of micas is not the sole feature for the micas of hydrothermal origin. (iii) As crystallization proceeds, the SiO2 concentration of the residual melt decreases, while the Al2O3 and F concentrations and A/CNK, NKA/Si ratios of the melt incerese, favoring the formation of Li-F-rich granites. Our experiment results are well consistent with the vertical zonation widely observed in rare metal bearing granites, and therefore provide strong experimental evidence for magmatic origin of Li-F-rich granite.

Deciphering the Origin of Abiotic Organic Compounds on Earth:Review and Future Prospects

The geologic production of abiotic organic compounds has been the subject of increasing scientific attention due to their use in the global carbon flux balance,by chemosynthetic biological communities,and for energy resources.Extensive analysis of methane(CH_(4))and other organics in diverse geologic settings,combined with thermodynamic modelings and laboratory simulations,have yielded insights into the distribution of specific abiotic organic molecules on Earth and the favorable conditions and pathways under which they form.This updated and comprehensive review summarizes published results of petrological,thermodynamic,and experimental investigations of possible pathways for the formation of particular species of abiotic simple hydrocarbon molecules such as CH_(4),and of complex hydrocarbon systems,e.g.,long-chain hydrocarbons and even solid carbonaceous matters,in various geologic processes,distinguished into three classes:(1)pre-to early planetary processes;(2)mantle and magmatic processes;and(3)the gas/water-rock reaction processes in low-pressure ultramafic rock and high-pressure subduction zone systems.We not only emphasize how organics are abiotically synthesized but also explore the role or changes of organics in evolutionary geological environments after synthesis,such as phase transitions or organic-mineral interactions.Correspondingly,there is an urgent need to explore the diversity of abiotic organic compounds prevailing on Earth.

A High Temperature and High Pressure Experimental Study on Re-Bearing Capability of Sulfide

High temperature（1 270–1 550 oC） and high pressure（1.0 GPa） experimental studies on Re-bearing capabilities of pyrite, galena and sphalerite from typical Pb-Zn ore deposits were performed on a six-anvil apparatus. We observed microstructures of the quenched sulfides using scanning electron microscope（SEM） and analyzed compositions of the run products using both energy disperse spectroscopy（EDS） and electron probe microanalyzer（EPMA）. The results show that pyrite melt can dissolve much more metallic Re than galena and sphalerite melts, forming scattered acicular ReS_2 in the quenched matrix of pyrrhotite（Fe_（1-x）S）. The quenched matrixes of Fe_（1-x）S, PbS and ZnS generally contain less than 1.0 wt.% of Re and their Re-bearing capabilities seem to range as Fe_（1-x）S〉Pb S〉Zn S. However, Re partition coefficients between them are difficult to estimate, because Re distribution is inhomogeneous in the quenched sulfide matrixes.

Competition mechanism of multiple four-wave mixing in highly nonlinear fiber： spatial instability and satellite characteristics

Competition mechanism in multiple four-wave mixing （MFWM） processes is demonstrated theoretically. Provided considering only two waves injected into a highly nonlinear fiber （HNLF）, there are three modes displaying comprehensive dynamic behaviors, such as fixed points, periodic motion, and chaotic motion. Especially, Mode C of MFWM is emphasized by analyzing its phase-space trajectory to demonstrate nonlinear wave- wave interactions. The study shows that, when the phase- space trajectory approaches or gets through a saddle point, a dramatic power depletion for the injected wave can be realized, with the representative point moving chaotically, but when phase-space trajectories are distributed around a center point, the power for the injected wave is retained almost invariable, with the representative point moving periodically. Finally, the evolvement of satellite wave over an optical fiber is investigated by comparing it with the interference pattern in Young＇s double-slit experiment.

Partial melting and crust-mantle interaction in subduction channels:Constraints from experimental petrology

It is proposed in the subduction channel model that the plate interface interaction is a basic mechanism for the mass and energy exchange between Earth’s surface and interior.The significant difference in composition and nature between continental lithosphere and oceanic lithosphere inevitably leads to variations in deep physical and chemical processes as well as crust-mantle interaction products in these two settings.Many studies of experimental petrology have provided constraints on the potential partial melting and crust-mantle interaction in oceanic subduction channels for silicate and carbonate rocks.The partial melts of mafic and felsic compositions are adakitic or non-adakitic granitic melts depending on melting pressure or depth.A trivial amount of CO2 can lower significantly the melting temperature of peridotites and lead to pronounced enrichment of incompatible elements in carbonate melt.The silica saturated or unsaturated melts can react with mantle-wedge peridotites in subduction channels to generate complex products.However,the existing experiments are mostly dedicated to island arc settings above oceanic subduction zones rather than dehydration melting above continental subduction zones.It is crucial to conduct high pressure and high temperature experiments to investigate all possible reactions between peridotites and crustal materials and their derivatives under the conditions responsible for the slab-mantle interface in continental subduction channels.Experimental results,combined with natural observations,are possible to elucidate the processes of metamorphic dehydration,partial melting and mantle metasomatism in continental subduction channels.

Rheological properties of deep subducted oceanic lithosphere and their geodynamic implications

According to the experimental studies on the rheology of two important mantle rocks (eclogite and harzburgite), the rheological properties of the deep subducted oceanic lithosphere are investigated by assuming a simplified harzburgite type slab model with moderate thickness of basaltic layer. When the mantle convergence rate is small or the subducting slab has been trapped in the mantle for an enough long time, the strength profile of the slab is characterized by a strong subducting crustal component lying on a weak subducting upper mantle. However, if the convergence rate is large enough, the subducting slab will be featured only by a rigid cold center. Our study suggests that the detachment of the subducting crust component from the underlying upper mantle is only likely to happen in hot slow subducting slabs, but not the cold fast subducting lithosphere. Rheological properties of the harzburgitic and the eclogitic upper mantle vary with depths. The eclogitic upper mantle is stronger than the peridotitic upper mantle across the upper mantle. Transition zone is the high strength and high viscosity layer in the upper mantle except the lithosphere.

Reaction Infiltration Instabilities in Partially Molten Peridotite and Implications for Driving the Transport of Sulfide Liquid

Reaction infiltration instability(RII)can cause the formation of melt channels and potentially facilitate the physical transport of sulfide liquid,which contributes to the geochemical evolution of chalcophile elements in the lithospheric mantle.This study conducted some two-layer reaction experiments to explore the feasibility of reaction-driven sulfide migration along high-velocity silicate-melt channels.With increasing duration,the formation of more silicate-melt channels and the transport of more sulfide droplets into a depleted peridotite were observed due to the increase of the local permeability.However,at a longer duration,the presence of some melt-channel relics implies that melt channels are temporary and ultimately closed when the reaction infiltration of silicate melt reached equilibrium in the depleted peridotite.Furthermore,theoretical calculations indicate that the RII of the system is suppressed,which impedes the formation of melt channels.The homogeneous distribution of silicate melt in a sulfide-free experiment implies that the Zener pinning of sulfide probably enhances the RII,thereby facilitating the formation of temporary melt channels.Therefore,this study demonstrates that sufficient silicate melt disequilibrium with solid phases in a liquid source potentially promotes the mechanical extraction of sulfides during reaction infiltration of silicate melt.