Petrogenesis and implications of jadeite‐bearing kyanite eclogite from the Sanbagawa belt (SW Japan)

Jadeite‐bearing kyanite eclogite has been discovered in the Iratsu body of the Sanbagawa belt, SW Japan. The jadeite + kyanite assemblage is stable at higher pressure–temperature (P–T) conditions or lower H₂O activity [a(H₂O)] than paragonite, although paragonite‐bearing eclogite is common in the Sanbagawa belt. The newly discovered eclogite is a massive metagabbro with the peak‐P assemblage garnet + omphacite + jadeite + kyanite + phengite + quartz + rutile. Impure jadeite is exclusively present as inclusions in garnet. The compositional gap between the coexisting omphacite (P2/n) and impure jadeite (C2/c) suggests relatively low metamorphic temperatures of 510–620 °C. Multi‐equilibrium thermobarometry for the assemblage garnet + omphacite + kyanite + phengite + quartz gives peak‐P conditions of ~2.5 GPa, 570 °C. Crystallization of jadeite in the metagabbro is attributed to Na‐ and Al‐rich effective bulk composition due to the persistence of relict Ca‐rich clinopyroxene at the peak‐P stage. By subtracting relict clinopyroxene from the whole‐rock composition, pseudosection modelling satisfactorily reproduces the observed jadeite‐bearing assemblage and mineral compositions at ~2.4–2.5 GPa, 570–610 °C and a(H₂O) >0.6. The relatively high pressure conditions derived from the jadeite‐bearing kyanite eclogite are further supported by high residual pressures of quartz inclusions in garnet. The maximum depth of exhumation in the Sanbagawa belt (~80 km) suggests decoupling of the slab–mantle wedge interface at this depth.     

陕西驾鹿金矿床地质特征及成因探讨

驾鹿金矿床是小秦岭金矿带中一个比较特殊的矿床类型，产于古老韧性剪切带中，围岩蚀变强烈而广泛，尤其是成脉前的钾长石化。蚀变带及其中的石英脉控制了金矿体的产出，矿床属蚀变岩型金矿，成矿时代为燕山晚期．本文在论述矿床地质特征的基础上，通过稳定同位素研究，认为燕山期构造热事件是成矿的主导控制因素，成矿溶液来自大气降水，成矿物质则部分来自太华群，部分来自上覆中元古界高山河组，矿床成因属大气降水热液矿床．     

The scattered disk as a source of Halley-type comets

We investigate a new dynamical mechanism for producing Halley-type comets from the scattered disk of comets. Levison and Duncan [Levison, H., Duncan, M., 1997. Icarus 127, 13-32] and Duncan and Levison [Duncan, M., Levison, H., 1997. Science 276, 1670-1672] showed that a significant number of objects leave the scattered disk by evolving to semi-major axes greater than 1000 AU. We find that once these objects reach semi-major axes on the order of ¹⁰⁴ AU, a significant fraction immediately have their perihelia driven inward by the galactic tides. Approximately 0.01% of the objects that reach ¹⁰⁴ AU then evolve onto orbits similar to the observed Halley-like comets due to gravitational interactions with the giant planets. The orbital element distribution resulting from this process is statistically consistent with observations. We discuss the implications of this model for the number of objects in the scattered disk in the text. The model predicts a temporal variation in the influx of HTCs with a period of ∼118 Myr. At the peak, the model predicts that there should be roughly 10 times as many HTCs as currently observed (i.e., there should be weak HTC showers). However, the model may inflate the importance of these showers because it does not include the effects of passing stars and giant molecular clouds.     

广西都结氧化锑矿可选性试验研究

都结锑矿的矿石矿物几乎均为黄锑矿 ,分布粒度微细 ,属难选的氧化矿石。经研究发现黄锑矿颗粒含3%的铁并具有弱磁性 ,采用分级强磁选与化学选矿相结合的试验流程 ,获得锑精矿品位 39.2 9% ,总回收率 >95 %的分选效果     

A rotational light curve for the Kuiper belt object 1997 CV29

We present R- and V-band rotational light curves for classical Kuiper belt object 1997 CV₂₉. The imaging data was obtained from the Canada-France-Hawaii Telescope (CFHT) archive located at the Canadian Astronomical Data Center (CADC). The data consist of one nights observations of a series of 42, 8 minute exposures in R band followed by 33, 8 minute exposures in V band acquired on the following night. Using relative photometry we determined a highly significant variation in the brightness of 1997 CV₂₉. Using phase-dispersion-minimization we find 8.0, 11.2, and 15.8 hrs to be the most likely, periods of rotation and we argue that the ∼16 hr period is the most likely based on our limited observing window. The phased light curve has a peak-to-peak range of Δm?0.4±0.1 mag suggesting an axial ratio of a/b?1.45.     

特级钾长石产品的半工业性选矿试验简介

根据山东省文登钾长石矿的矿石物质组成和工艺特性 ,经过不同选别方法、不同药剂种类、不同药剂用量的试验 ,确定了较佳选矿工艺 ,并以此为基础进行了半工业型试验。最终获得了特级钾长石产品。     

Diverse albedos of small trans-neptunian objects

Discovery of trans-neptunian object (TNO) satellites and determination of their orbits has recently enabled estimation of the size and albedo of several small TNOs, extending the size range of objects having known size and albedo down into the sub-100 km range. In this paper we compute albedo and size estimates or limits for 20 TNOs, using a consistent method for all binary objects and a consistent method for all objects having reported thermal fluxes. As is true for larger TNOs, the small objects show a remarkable diversity of albedos. Although the sample is limited, there do not yet appear to be any trends relating albedo to other observable properties or to dynamical class, with the possible exception of inclination. The observed albedo diversity of TNOs has important implications for computing the size-frequency distribution, the mass, and other global properties of the Kuiper belt derived from observations of objects' apparent magnitudes and may also point the way toward an improved compositional taxonomy based on albedo in addition to color.     

河南小秦岭金矿控矿条件分析及找矿前景

本文从矿源层控矿构造、区域变质、混合岩化、岩浆作用及多期次的热液成矿叠加作用等方面对金矿的控矿条件进行了较深入的分析，进一步提出了淘金沟─贵家峪一带为找金远景区；在文峪的深部可能有糜棱岩型或黄铁矿型金富集段的存在。     

蒙特卡罗法在资源评价中的应用

结合陕西灞源地区金矿预测实例,探讨了在蒙特卡罗法应用中潜在矿床总数估计及资源总量概率分布向资源潜力分布转换两个环节的合理实现方法。在一定条件下,矿点空间分布模型和发现过程模型可有效地用于估计潜在矿床总数。通过坐标平移或求截尾分布而将资源总量的概率分布转变为资源潜力的概率分布,可得到较为符合地质实际的评价结果。     

胶南-威海造山带与罗迪尼亚(Rodinia)超大陆相关问题的初步探讨

胶南-威海造山带中的榴辉岩为晋宁早期板块俯冲作用的产物;沿造山带广泛分布的花岗质片麻岩,则为晋宁晚期板块由俯冲转为碰撞过程中同造山岩浆事件的产物.它们与全球性的格林威尔造山运动属同一事件范畴,但具有明显的穿时性.侵入于同造山花岗质片麻岩的片麻状花岗岩及震旦纪朋河石组,为后造山伸展机制下发生的岩浆及沉积事件的产物,与700～650Ma期间Rodinia超大陆的裂解作用密切相关.