Accretion and exhumation at a Variscan active margin, recorded in the Saxothuringian flysch

The Saxothuringian flysch basin, on the north flank of the Central European Variscides, was fed and eventually overthrust by the northwestern, active margin of the Tepla-Barrandian terrane. Clast spectra, mineral composition and isotopic ages of detrital mica and zircon have been analyzed in order to constrain accretion and exhumation of rocks in the orogenic wedge. The earliest clastic sediments preserved are of early Famennian age (ca. 370?Ma). They are exposed immediately to the NW of the suture, and belong to the par-autochthon of the foreland. Besides ultramafic (?ophiolite) material, these rocks contain clasts derived from Early Paleozoic continental slope sediments, originally deposited at the NW margin of the Saxothuringian basin. These findings, together with the paleogeographic position of the Famennian clastics debris on the northwestern passive margin, indicate that the Saxothuringian narrow ocean had been closed by that time. Microprobe analyses of detrital hornblendes suggest derivation from the “Randamphibolit” unit, now present in the middle part of the Saxothuringian allochthon (Münchberg nappes). Detrital zircons of metamorphic rocks formed a little earlier (ca. 380?Ma) indicate rapid recycling at the tectonic front. The middle part of the flysch sequence (ca. early to middle Viséan), both in the par-autochthon and in the allochthon, contains abundant clasts of Paleozoic rocks derived from the northwestern slope and rise, together with debris of Cadomian basement, 500-Ma granitoids and 380?Ma (early Variscan) crystalline rocks. All of these source rocks were still available in the youngest part of the flysch (c. middle to late Viséan), but some clasts record, in addition, accretion of the northwestern shelf. Our findings permit deduction of minimum rates of tectonic shortening well in excess of 10–30?mm per year, and rates of exhumation of ca. 3?mm/a, and possibly more.     

地质速率计—矿物氧扩散的应用

概述了同位素封闭体系内的矿物氧扩散和同位素交换机制及其在地质速率计上的应用。火成岩从高温冷却或变质岩从高峰主质温度冷却过程中，由于冷却速度不同，扩散作用导致的矿物晶体内部及晶粒间氧同位素再平衡也有所不同。通过实测岩石中各组成矿物氧同位素比值，模式含量和颗粒半径，据矿物氧扩散和同位素交换模型，可以估算出岩石的冷却速率。     

榴辉岩的化学分类

以山东荣成地区的榴辉岩为例,把榴辉岩分为镁一榴辉岩、铁一榴辉岩和钙一榴辉岩三类。三类榴辉岩的岩石化学,主要造岩矿物成分都有明显差别,石榴石分别是镁铝榴石、铁铝榴石和钙铝榴石。绿辉石的硬玉分子也有不同。三类榴辉岩的化学成分限制是Mg-榴辉岩MgO>10%,石榴石以镁铝榴分子占优势,Fe-榴辉岩的MgO<10,石榴石以铁铝榴石分子占优势。Ca-榴辉岩CaO>19%,石榴石以钙铝榴石分子优势。     

试论矿产勘查中人的决定性因素

矿产勘查是一项系统工程，由多种因素构成，要想获得尽可能高的矿产勘查成果，仅依靠先进的成矿理论和找矿方法是不够的，还需注重掌握先进成矿理论与方法的管理人员的作用，在地勘行业调整与改革的现阶段，强调矿产勘查系统中人的决写性因素，认识人在矿产勘查中的地位与作用，提高勘查人员的素质，对调整，稳定发展地勘队伍具有一定的现实意义。     

关于当前我国战略性矿产勘查工作几个问题的思考

战略性矿产勘查是近几年根据中国地勘管理体制的新变化和国家对矿产勘查工作的新要求提出的概念。本文从战略性矿产的基本内涵、战略性矿产资源勘查工作的性质与任务、战略性矿产资源勘查工作与传统矿产勘查工作的差异、战略性矿产资源勘查工作的管理体制与运行机制等几个方面进行了初步探讨，旨在明确其性质定位和目标任务，逐步建立国家出资的公益性地质工作与后续商业性矿产勘查工作良性互动、有机结合的有效机制，促进中国矿产勘查业全面、健康地发展。     

论江苏若干矿产资源开发利用的新方向

江苏泥炭大多数为低有机质分解较强的低位泥炭，适于制作肥料或制成腐肥使用；江苏硅质原料丰富，一种以硅为主的化肥——硅肥正日益显示其重要性；湖泊淤泥具有颗粒微细、含砂量少、可塑性高、结合力强、干燥敏感性好和收缩率较大等特点，是生产空心砖的最佳原料；高家边组泥页岩和坟头组底部细粉砂质泥岩及泥质粉砂岩是良好的陶粒原料、砖瓦、陶瓷建材以及水泥用粘土质原料；利用矿泉水与茶的结合能够生产出高、中、低多效应的复合型新产品。上述尚未被利用或利用程度不够的矿产资源有着广泛的开发利用前景。     

云南白秧坪矿化集中区矿石矿物特征及银、钴赋存状态的初步研究

云南白秧坪地区是以银、钴多金属矿化为特色的矿集区，成矿作用与兰坪盆地两侧的推覆构造系统密切相关，发育一套复杂的中低温热液矿物组合，出现了铜、钴、镍、铋等亲地幔元素的硫化物(硫钴镍矿、硫铋铜矿)，显示地幔深源物质可能参与了成矿作用。银、钴赋存状态的初步研究表明载银矿物主要为汞银矿、辉银矿、银黝铜矿、方铅矿、黝铜矿及砷、锑、铅硫盐矿物等，载钴矿物主要为硫钴镍矿、辉砷钴矿、含钴毒砂等硫化物。     

Indicator mineralogy of kimberlite boulders from eskers in the Kirkland Lake and Lake Timiskaming areas, Ontario, Canada

Sixteen kimberlite boulders were collected from three sites on the Munro and Misema River Eskers in the Kirkland Lake kimberlite field and one site on the Sharp Lake esker in the Lake Timiskaming kimberlite field. The boulders were processed for heavy-mineral concentrates from which grains of Mg-ilmenite, chromite, garnet, clinopyroxene and olivine were picked, counted and analyzed by electron microprobe. Based on relative abundances and composition of these mineral phases, the boulders could be assigned to six mineralogically different groups, five for the Kirkland Lake area and one for the Lake Timiskaming area. Their indicator mineral composition and abundances are compared to existing data for known kimberlites in both the Kirkland Lake and Lake Timiskaming areas. Six boulders from the Munro Esker form a compositionally homogeneous group (I) in which the Mg-ilmenite population is very similar to that of the A1 kimberlite, located 7–12 km N (up-ice), directly adjacent to the Munro esker in the Kirkland Lake kimberlite field. U–Pb perovskite ages of three of the group I boulders overlap with that of the A1 kimberlite. Three other boulders recovered from the same localities in the Munro Esker also show some broad similarities in Mg-ilmenite composition and age to the A1 kimberlite. However, they are sufficiently different in mineral abundances and composition from each other and from the A1 kimberlite to assign them to different groups (II–IV). Their sources could be different phases of the same kimberlite or—more likely—three different, hitherto unknown kimberlites up-ice of the sample localities along the Munro Esker in the Kirkland Lake kimberlite field. A single boulder from the Misema River esker, Kirkland Lake, has mineral compositions that do not match any of the known kimberlites from the Kirkland Lake field. This suggests another unknown kimberlite exists in the area up-ice of the Larder Lake pit along the Misema River esker. Six boulders from the Sharp Lake esker, within the Lake Timiskaming field, form a homogeneous group with distinct mineral compositions unmatched by any of the known kimberlites in the Lake Timiskaming field. U–Pb perovskite age determinations on two of these boulders support this notion. These boulders are likely derived from an unknown kimberlite source up-ice from the Seed kimberlite, 4 km NW of the Sharp Lake pit, since indicator minerals with identical compositions to those of the Sharp Lake boulders have been found in till samples collected down-ice from Seed. Based on abundance and composition of indicator minerals, most importantly Mg-ilmenite, and supported by U–Pb age dating of perovskite, we conclude that the sources of 10 of the 16 boulders must be several hitherto unknown kimberlite bodies in the Kirkland Lake and Lake Timiskaming kimberlite fields.     

An experimental study on felsic rock–artificial seawater interaction: implications for hydrothermal alteration and sulfate formation in the Kuroko mining area of Japan

Experimental studies on the interactions between artificial seawater (ASW) and fresh rhyolite, perlite and weakly altered dacitic tuff containing a small amount of smectite suggest changing cation transfer during smectite-forming processes. Initially, dissolution of K from the rocks accompanies incorporation of Mg and Ca from ASW during both earlier (devitrification stage) and later smectite formation, whereas Ca incorporated with early smectite formation redissolves with progressive reaction. Barium mobility increases toward the later smectite-forming reactions. Therefore, the large amounts of barite, anhydrite and gypsum in Kuroko ore deposits are considered to have precipitated from hydrothermal solutions derived from the interaction with previously altered felsic rocks during late smectite formation, rather than by the reaction with fresh felsic rocks.Editorial handling: D. Lentz     

Glacial dispersal studies using indicator minerals and till geochemistry around two eastern Finland kimberlites

Diamondiferous kimberlites occur in eastern Finland, in the areas of Kaavi–Kuopio and Kuhmo. Active diamond exploration has been ongoing in the country for over two decades, but the Karelian craton still remains under explored given its size and potential. In order to develop techniques that can be applied to diamond exploration in glaciated terrains, the Geological Survey of Finland (GTK) carried out a detailed heavy mineral and geochemical survey of Quaternary till in 2001–2003 around two of the known kimberlitic bodies in Finland, Pipe 7 in Kaavi and Dyke 16 in Kuhmo. The mineralogical and geochemical signatures of these two kimberlites were studied in the basal till deposited down-ice from the targets. The kimberlites were selected to represent two different types in terms of shape, size, age and petrology, as well as showing contrasting country rocks and Quaternary deposits. Till samples up to 60 kg in weight were taken by excavator and by drill rig. Kimberlitic indicator mineral grains (0.25–1.0 mm) were concentrated using a GTK modified 3″Knelson Concentrator. Fine fractions (< 0.063 mm) of selected samples were analyzed by XRF and ICP-MS. The indicator grains down-ice from Pipe 7 form a well-defined fan in the basal till that can be followed for at least 2 km with a maximum concentration at 1.2 km distance from the pipe. Another kimberlitic body discovered during the study 300 m down-ice from Pipe 7 demonstrates that there are in fact at least two superimposed indicator fans. The results do not rule out the possibility of even more undiscovered kimberlitic sources in the area. In contrast, the indicator dispersal trail from Dyke 16 is shorter (1 km) and less well-defined than that at Kaavi, mainly due to the lower indicator content in the kimberlite itself and subsequently in till, as well as a large population of background chromites in till. The latter population is likely having been derived from the Archean Näätäniemi serpentinite massif and the associated ultramafic metavolcanics of the Kuhmo greenstone belt, located ca. 30 km up-ice from the sampling area. The indicator maximum at Seitaperä dyke swarm occurs immediately down-ice from the kimberlite, after which the concentration drops rapidly. Results of this study contribute to the overall understanding of the Quaternary history of the Kaavi and Kuhmo areas, and more importantly, provide key information to diamond exploration in these particular regions and also elsewhere in glaciated terrains.