辽西热河生物群中的水虿化石新发现

本文描述了热河生物群中2个水虿新种：Gomphus? biconuexus sp．nov,和Aeschna?acrodonta sp．nov．,它们分别属于Gomphidae科和Aeshnidae科。化石采自辽西北票黄半吉沟义县组下部(晚侏罗世-早白垩世早期)。     

辽西地区义县组昆虫化石及其生物地层、古生态学意义

作为热河昆虫群的重要组成部分,辽西地区义县组昆虫化石内容独特、丰富,共有49科83属,明显区别于同属热河昆虫群的大北沟组和九佛堂组,生物地层单位称为Epheeropsis trisetalis-Sinaeschnidia cancellosa组合,时代为晚侏罗世晚期-早白垩世早期.昆虫群反映了当时温暖而潮湿的气候环境及因地形不同引起的小气候的存在.     

辽西北票地区中-晚侏罗世土城子组恐龙足迹化石的发现

辽西朝阳北票南八家子附近中-晚侏罗世土城子组发现了大量恐龙足迹化石(兽脚类、鸟脚类、蜥脚类).本文主要对兽脚类恐龙足迹做了报道.兽脚类恐龙为两足行走,三趾型、窄行迹、多数为趾行式,化石均为上层面保存.层面发育泥裂和波痕.足迹大小从29.5cm×19cm到4cm×3cm,连续分布的足迹构成明显的行迹,行迹方向规律性分布为当时恐龙的行为习性提供了可靠证据.南八家子地区发现的大量小型兽脚类恐龙足迹表明:在北票地区小型兽脚类恐龙在中晚侏罗世土城子期已经出现.     

辽西北票中晚侏罗世髫髻山组木化石的古气候、古环境和古生态意义

木化石在陆地生态系统古气候、古环境和古生态研究方面具有重要的意义。辽西北票地区中晚侏罗世髫髻山组保存有数量丰富、类型多样且解剖构造保存完好的木化石。基于北票木化石树木年轮、树桩直径等数据计算了木材早材与晚材的比率(E/L),并推算了松柏类树木古树高。通过已有测量的树木年轮直径,应用Niklas(1994)和Mosbrugger(1994)两种方法恢复了化石森林中松柏类树木的古树高约为25m。推断中晚侏罗世的裸子植物森林树木生长的环境为以火山岩和湖相沉积为主,降水丰富。推断髫髻山组属于温暖、湿润、季节性明显的亚热带到暖温带气候,有利于植物的生长与发育。木化石木材组织中呈现的特殊解剖构造包括假轮、创伤树脂道、年轮扭曲、虫孔等,也能够揭示辽西北票中晚侏罗世植物生长过程中的古气候与古环境状况。表明辽西北票地区中晚侏罗世古气候虽然有利于植物生长,但生长期间受到了火山喷发、虫害、大风、降温等多种不利气候变化的影响与干扰。     

中国陆相侏罗系—白垩系界线及其国际地层对比——以冀北—辽西地区侏罗系—白垩纪年代地层为例

冀北—辽西地区陆相侏罗系—白垩系发育,各类生物化石丰富,并夹有火山岩,是利用岩石地层、生物地层、同位素测年和磁性年代地层综合研究侏罗系\白垩系界线的理想地区。冀北滦平盆地侏罗系\白垩系界线附近的地层为大北沟组和大店子组,辽西义县—北票地区侏罗系\白垩系界线附近的地层为土城子组和义县组。大店子组含有孢粉Cicatricosisporites-Luanpingspora-Jugella组合;介形类Yanshanina-Cypridea-Rhinocypris组合,Cypridea-Yanshanina-Timiriasevia组合,Cypridea sulcata亚组合和叶肢介Eosestheria-Abrestheria组合等各类化石,这些生物组合与国内、外的对比,尤其是孢粉和介形类与英、法、德、俄和加拿大等地相关地层同类化石组合的对比,其时代为早白垩世早期(Berriasian)。辽宁西部义县组下部的孢粉、介形类和叶肢介与国内、外的对比,也得出与大店子组的时代大致相同的结论。大北沟组含孢粉Poceites-Podocarpidites-Schizaeoisporites组合,介形类Luanpingella-Torinina-Eoparacypris组合以及叶肢介Nestoria-Keratestheria组合等,这些生物组合与国内、外同类生物组合的对比,得出的时代结论是晚侏罗世晚期(Tithonian)。土城子组含有孢粉、介形类及叶肢介等6大门类化石,根据已有的研究成果,得出的时代结论是晚侏罗世。因此,侏罗系\白垩系的界线划在大北沟组与大店子组之间。生物地层的国际对比表明:此界线与国际侏罗系\白垩系界线,即Tithonian\Berriasian界线是一致的。根据冀北—辽西地区一系列同位素测年数据推断,侏罗系\白垩系界线年龄应接近130.7Ma。     

中国陆相侏罗系—白垩系界线及其国际地层对比——以冀北—辽西地区侏罗系—白垩系年代地层为例

冀北—辽西地区陆相侏罗系—白垩系发育,各类生物化石丰富,并夹有火山岩,是利用岩石地层、生物地层、同位素测年和磁性年代地层综合研究侏罗系\\白垩系界线的理想地区。冀北滦平盆地侏罗系\\白垩系界线附近的地层为大北沟组和大店子组,辽西义县—北票地区侏罗系\\白垩系界线附近的地层为土城子组和义县组。大店子组含有孢粉Cicatricosisporites Luanpingspora Jugella 组合;介形类Yanshanina Cypridea Rhinocypris组合,Cypridea Yanshanina Timiriasevia组合,Cypridea sulcata亚组合和叶肢介Eosestheria Abrestheria组合等各类化石,这些生物组合与国内、外的对比,尤其是孢粉和介形类与英、法、德、俄和加拿大等地相关地层同类化石组合的对比,其时代为早白垩世早期（Berriasian）。辽宁西部义县组下部的孢粉、介形类和叶肢介与国内、外的对比,也得出与大店子组的时代大致相同的结论。大北沟组含孢粉Poceites Podocarpidites Schizaeoisporites组合,介形类Luanpingella Torinina Eoparacypris组合以及叶肢介Nestoria Keratestheria组合等,这些生物组合与国内、外同类生物组合的对比,得出的时代结论是晚侏罗世晚期（Tithonian）。土城子组含有孢粉、介形类及叶肢介等6大门类化石,根据已有的研究成果,得出的时代结论是晚侏罗世。因此,侏罗系\\白垩系的界线划在大北沟组与大店子组之间。生物地层的国际对比表明：此界线与国际侏罗系\\白垩系界线,即Tithonian\\Berriasian界线是一致的。根据冀北—辽西地区一系列同位素测年数据推断,侏罗系\\白垩系界线年龄应接近1307Ma 。     

辽西建昌县玲珑塔含翼龙和带羽毛恐龙化石地层层序和时代归属

最近辽西建昌地区报道发现了一系列带羽毛恐龙和翼龙化石, 其赋存化石的地层层位时代一直富有争议。我们结合前人资料对玲珑塔含化石地层剖面进行了野外调查和实测, 厘定了含化石地层沉积层序和时代归属。剖面顶底岩石组合特征主要以溢流相中性熔岩和近火山口相火山碎屑岩为主, 中间层位为河流相-湖泊相碎屑岩。该剖面产有大量叶肢介、介形类、双壳类、昆虫、鱼类、植物化石和大量脊椎动物化石。上述化石指示含恐龙化石地层时代为中侏罗世。通过区域对比认为含恐龙化石地层与区域上髫髻山组地层层序和岩石组合相似, 因此认为含恐龙化石地层为中侏罗世髫髻山组(火山岩同位素年代学年龄范围为152~165 Ma)。     

辽西朝阳地区含鸟化石层附近侏罗—白垩系磁性地层研究

本文通过对辽西朝阳地区含鸟化石层附近侏罗-白垩系蓝旗组、土城子组、义县组地层共1252块古地磁样吕的测试与分析，建立了以上沉积地层的磁极性序列，发现蓝旗组、土城子组地层的磁极性序列具有频繁的正、反极性、而义县组则为单一正极性，结合现有古生物和同位素年龄资料，对比国际中生代地磁极性年表，表明土城子组的磁极性序列相当于提塘期、基末里期、牛津期和卡洛期，其主体的地质时代应属晚侏罗世（J3），土城子组底部的地质时代应属中侏罗世（J2)；并且根据义县组含鸟化石层以上层位的磁性地层研究结果，认为义县组含鸟化石的正极性带可与M16正极性时相对应，义县组含鸟类化石层的时代应属早白垩世早期，辽西白垩系/侏罗系界线很有可能位于义县组/土城子组之间。     

长羽毛恐龙及翼龙研究新发现

在江西赣州地区晚白垩世地层中发现的窃蛋龙类化石——赣州华南龙,属于进步窃蛋龙类,其独特的头部特征为研究窃蛋龙类恐龙的颅面演化、古地理分布及古生态环境提供重要信息;在辽西早白垩世义县组地层中发现的大型、前肢短的驰龙类恐龙——孙氏振元龙,为大型、短前肢类型的驰龙类提供羽毛形态学方面的重要信息,为研究驰龙类的多样性、鸟类羽毛以及飞行起源提供了重要依据;在辽西发现的喙嘴龙类翼龙——朝阳东方颌翼龙,是该地区晚侏罗世地层中发现的第一件翼龙标本,不仅填补了时代上的空白,同时对于印证晚侏罗世喙嘴龙类的辐射演化具有重要作用。这些重要发现对于研究窃蛋龙类的演化、驰龙类羽毛演化及鸟类羽毛起源等热点与难点问题提供了重要的参考依据,尤其在发现华南龙的基础上,命名了赣州恐龙动物群。     

辽宁凌源中生代鸟类化石一新属

近年来,辽宁西部及其邻区中生代大量原始鸟类化石及其祖先类型的发现(季强等,1996;侯连海,1997;Ji et al,1998),使我们对鸟类的起源和早期演化有了新的更加全面的认识。本文简要记述一件产自辽西凌源“义县组”的鸟类化石,与该鸟类保存在一起的戴氏狼鳍鱼(Lycoptera davi-di)等化石,为确定该鸟类的时代为晚侏罗世提供了依据。这是辽西冀北一带晚侏罗世鸟类化石的     

Reply: Middle Pleistocene sedimentation at Pakefield,Suffolk, England: a response to Lee et al. (2006) P. L. Gibbard,A. Moscariello,H. W. Bailey,S. Boreham,C. Koch,A. R. Lord,J. E. Whittaker,C. A. Whiteman

Journal of Quaternary Science Published online 9 August 2007. DOI: 10.1002/jqs.1118 The above paper was incorrectly titled. The correct title should be: Comment: Middle Pleistocene sedimentation at Pakefield, Suffolk, England J. R. LEE, J. ROSE, I. CANDY and R. W. BARENDREGT (2006) Journal of Quaternary Science 21 : 155–179 The error will be corrected prior to print publication.     

Mineralogy, Petrology, and Geochemistry of an Ultrapotassic Basaltic Suite, Central Sierra Nevada, California, U.S.A.

Ultrapotassic basaltic lavas erupted 3.4–3.6 m.y. ago(K/Ar) in the central Sierra Nevada and originated by partialmelting of a phlogopite-enriched, garnet-bearing upper mantlesource. Ultrapotassic basanites (K₂O: 5–9 per cent), whichare spatially related to contemporaneous potassic olivine basalts(K₂O: 3–5 per cent) and alkali olivine basalts (K₂O: 1–3per cent), contain the K₂O-bearing minerals phlogopite, sanidine,and leucite as well as olivine, diopside, apatite, magnetite,and pseudobrookite. The presence and modal abundance of theK₂O-bearing minerals closely reflects the east to west increasein K₂O throughout the basaltic suite. Many lines of evidence support the derivation of the ultrapotassicbasanites and the related basalts from an upper mantle source:TiO₂ in phlogopite phenocrysts and groundmass crystals, 2–3and 7–9 per cent respectively, support phlogopite phenocrystcrystallization at high pressure, whole rock Mg values (100Mg/Mg + 0.85 Fe) range from 66–78, phlogopite-rich pyroxeniticand periodotitic nodules are included in some flows, and geobarometriccalculations indicate depths of generation at 100–125km. Also, model calculations show that the major, rare earth,and trace elements, except for Ba, Rb, and Sr, can be accuratelygenerated by 1.0–2.5 per cent melting of a phiogopite-and garnet-bearing clinopyroxene-rich upper mantle source. Partialmelting occurred after a general upper mantle enrichment beneaththe Sierra Nevada, the phlogopite- and clinopyroxene-rich sourceof the ultrapotassic lavas being the extreme result of the enrichmentprocess. Clinopyroxene enrichment of the upper mantle probablyoccurred by introduction of a partial melting fraction intothe upper mantle source areas. Enrichment of the upper mantlein the alkali and alkali-earth elements was not accomplishedby a partial melt, but resulted from influx of a fluid phaserich in Ba, K, Rb, Sr, and, probably, H₂O The continuous rangein K₂O of the erupted lavas implies that the upper mantle enrichmentis a cumulative process. The inverse relationship in the SierraNevada between uplift and the K₂O content of the erupted basaltsimplies that a critical relationship may exist between upliftand upper mantle enrichment.     

Geochemistry and petrogenesis of lamproites,late cretaceous age,Woodson County,Kansas, U.S.A.

Lamproite sills and their associated sedimentary and contact metamorphic rocks from Woodson County, Kansas have been analyzed for major elements, selected trace elements, and strontium isotopic composition. These lamproites, like lamproites elsewhere, are alkalic (molecular $\text{K}{}_2\text{O + Na}{}_2\text{O}\text{Al}{}_2\text{O}{}_3\text{= 1.6–2.6}$), are ultrapotassic $\text{(}\text{K}{}_2\text{O}\text{Na}{}_2\text{O}\text{= 9.6–150)}$, are enriched in incompatible elements (LREE or light rare-earth elements, Ba, Th, Hf, Ta, Sr, Rb), and have moderate to high initial strontium isotopic compositions (0.7042 and 0.7102). The silica-saturated magma (olivine-hypersthene normative) of the Silver City lamproite could have formed by about 2 percent melting of a phlogopite-garnet lherzolite under high $\text{H}{}_2\text{O}\text{CO}{}_2$ ratios in which the Iherzolite was enriched before melting in the incompatible elements by metasomatism. The Rose Dome lamproite probably formed in a similar fashion although the extreme alteration due to addition of carbonate presumably from the underlying limestone makes its origin less certain. Significant fractional crystallization of phases that occur as phenocrysts (diopside, olivine, K-richterite, and phlogopite) in the Silver City magma and that concentrate Co, Cr, and Sc are precluded as the magma moved from the source toward the surface due to the high abundances of Co, Cr, and Sc in the magma similar to that predicted by direct melting of the metasomatized Iherzolite.Ba and, to a lesser extent, K and Rb and have been transported from the intrusions at shallow depth into the surrounding contact metamorphic zone. The Silver City lamproite has vertical fractionation of some elements due either to volatile transport or to variations in the abundance of phenocrysts relative to groundmass most probably due to flow differentiation although multiple injection or fractional crystallization cannot be conclusively rejected.     

安徽铜陵老鸦岭层状铜矿床的成矿地球化学研究

安徽铜陵老鸦岭铜矿床是长江中下游地区的一个典型的层状矿床，以远离侵入岩体和赋存于二叠系钙质－硅质岩中为特征，其矿石矿物组合简单，近矿围岩蚀变较弱，为绢云母化、高岭石化、碳酸盐化和绿泥石化等，且分带性不明显。按照矿物形成的时间序列，矿床矿物可分为四个共生组合：（1）磁黄铁矿＋黄铁矿组合；（2）黄铜矿＋黄铁矿＋闪锌矿＋磁黄铁矿组合；（3）石英＋黄铜矿组合；（4）方解石＋黄铜矿组合。矿物包裹体以气液两相为主，气液比从早到晚逐渐减小直至成为单一的液相。均一法测温表明，组合1的均一温度为290～320℃，组合2为240～265℃，组合3为180～220℃，和组合4为110～116℃。矿物包裹体液相成分属于NaCl－H_2O体系，并含有F~－和，盐度小于10wt％。根据热力学计算，圈定了矿物共生组合的物理化学场，从组合1到4，成矿热液的fo_2、fs_2及∑S浓度依次降低，pH值变化不大，但还原性降低，氧化性增强。矿床硫同位素组成δ~34S_∑S为：组合1是＋0．5％。，组合2为1‰～3‰，组合3大于＋5‰和组合4大于＋6‰。这证实成矿热液中硫来源于岩浆，并随着时间的演化有地层硫的加入。氧和氢同位素研究说明参与成矿作用的热液除岩浆源之外，还有相当多的大气水或地下水的加入。矿石普通铅同位素为异常     

Petrochemistry of the Fish Cove rhyolite,Keweenaw peninsula,Michigan, U.S.A.

A small (360 × 180 m) rhyolitic intrusive body in the lower portion of the Portage Lake Lava Series of Michigan's Keweenaw peninsula was mapped and sampled in detail. The rhyolite is one of a number of similar bodies which make up less than 1% of the total volume of this thick Late-Precambrian plateau basalt pile. The rock is a low-calcium rhyolite with fine-grained homogeneous texture and sparse phenocrysts of plagioclase and quartz. Analyses of selected trace and major elements for 21 samples taken from the body reveal a chemical zonation consisting of a core zone enriched in K, Rb and Ba, and a border zone relatively poor in these elements. Little areal difference is found with respect to other elements tested (Mn, Sr, Zr, Ca, Ti, and Fe). This apparently primary zonation seems to result from the migration of K, Rb and Ba during crystallization of the shallow intrusive. Though zoned, the trace-element chemistry of the Fish Cove body is distinct from that of eight other rhyolites in the Portage Lake Lava Series, and suggests that fingerprinting by trace elements might be a fruitful method for identifying and correlating the sources of numerous rhyolitic pebbles in conglomerates interbedded with the basaltlava flows of the Portage Lake Series.     

Origin and mixing history of brines,Palo Duro Basin,Texas, U.S.A.

Formation waters in the Palo Duro Basin, Texas, U.S.A. fall into four major groups based on integrated chemical and isotopic characteristics: (1) interbed brines within the major Permian evaporite aquitard; these are the most chemically concentrated and¹⁸O-rich fluids in the basin, and are interpreted as evaporatively concentrated sea water which has been hydrologically isolated since the Permian; (2) brines below the salt on the eastern side of the basin have ClBr, divalent cation, and isotopic systematics indicating a mixture of evaporatively concentrated sea water and meteoric water of δD= −20‰; (3) brines below the salt on the western side of the basin have chemical and isotopic systematics suggesting a mixture of two pulses of meteoric water, one with δD= −20‰ and the other with δD= −55‰; and (4) waters above the salt have the isotopic composition of meteoric waters. Diagenetic alteration of the cation chemistry has occurred for brines within and below the salt. Aquifers below the salt on the eastern side are interpreted as having been charged with dense Permian evaporite brines which subsequently mixed in various amounts with a basin-wide pulse of Triassic meteoric water. On the western side the descending Triassic meteoric waters became saline by dissolution of halite and are currently mixing with a Tertiary pulse of meteoric water initiated by the Laramide uplift to the west. The hydrochemistry suggests flow on the western side of the basin and static conditions on the eastern side. An unrecognized, approximately N-S permeability restriction, or discontinuity in the potentiometric flow surface, is inferred for major aquifers in the central area of the basin.     

The mineralogy of the Golden Sunlight gold-silver telluride deposit, Whitehall, Montana, U.S.A.

Summary The Golden Sunlight gold-silver telluride deposit, hosted primarily within the Mineral Hill breccia pipe (MHBP), is spatially related to a high-level, Late Cretaceous multiple intrusive, alkaline to subalkaline porphyry system. Base metal veins and manganese (rhodochrosite) mineralization occur up to 2km from the MHBP and form part of a regional mineral zonation pattern genetically related to a low-grade porphyry molybdenum system. Proterozoic rocks of the LaHood Formation and the informally named Bull Mountain Group host the MHBP and contain stratabound sulphides/ sulphosalts (up to 50% pyrite with minor to trace amounts of chalcopyrite, tennantite, pyrrhotite, sphalerite, galena, and molybdenite). Four periods of hypogene mineralization occur in the breccia pipe. Stages I and IV constitute ,99% of the mineralization; native gold (4–11 wt.% Ag), calaverite, tetradymite, tellurobismuthite, Se-bearing Bi sulphosalts (aikinite, lindströmite, krupkaite, gladite, bismuthinite, and ?benjaminite), tennantite (Zn, Fe, Te, and Bi varieties), coloradoite, melonite, galena (up to 6.7 wt.% Bi and 6.4 wt.% Se), stannite, chalcocite, and the rare mineral buckhornite are included in stage Ib. Minor amounts of base metals are present in stage II. Gold-silver tellurides (krennerite, petzite, sylvanite, and possibly the rare x-phase) developed in stage III whereas barite, fluorite, dolomite, magnesite, trace kaolinite, and sericite formed during stage IV. Utilizing the mineral assemblages in stage Ib, calculated values of logf Te₂ and logf S₂ range from -10.5 to -9.7, and -12.6 to -5.5, respectively.Ore forming components (e.g., Au, Ag, Te, Cu, Bi, Mo, and much of the S) were likely derived from the Late Cretaceous intrusive system with possible contributions from the Proterozoic host rocks.

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Mineralogie der Golden Sunlight Gold-Silber-Tellurid-Lagerstätte, Whitehall, Montana

Zusammenfassung Die Golden Sunlight Gold-Silber-Tellurid-Lagerstätte, die hauptsächlich im Brekzienschlot von Mineral Hill (Mineral Hill breccia pipe, MHBP) eingelagert ist, steht räumlich mit einem erzreichen, multi-intrusiven, alkalischen bis sub-alkalischen Porphyritsystem aus der Oberkreide in Beziehung. Erzadern und Mn-Mineralisation (Rhodochrosit) finden sich bis zu 2 km vom MHBP entfernt und sind Bestandteil einer regionalen Vererzung die genetisch zu einem erzarmen Mo-hältigen Porphyritsystem in Beziehung steht. Proterozoische Gesteine aus der LaHood-Formation und der inoffiziell benannten Bull Mountain Group umgeben den MHBP und enthalten schichtgebundene Sulfide und Sulfosalze (bis zu 50% Pyrit mit Neben- bis Spurenmengen von Kupferkies, Tennantit, Pyrrhotin, Zinkblende, Bleiglanz und Molybdänit).[Der Brekzienschlot zeigt vier Phasen hypogener Mineralisation. Stufen I und IV enthalten 99% der Mineralisation: gediegen Gold (4–11 Gew.% Ag), Calaverit, Tetradymit, Tellurobismuthit, Se-hältige Bi-Sulfosalze (Aikinit, Lindströmit, Krupkait, Gladit, Bismuthinit und ?Benjaminit) Tennantit (Zn-, Fe-, Te- und Bi-Varietäten), Coloradoit, Melonit, Bleiglanz (mit bis zu 6.7 Gew.% Bi und 6.4 Gew.% Se), Zinnstein, Chalcocit, sowie das seltene Mineral Buckhornit treten in Stufe Ib auf. Geringere Mengen von Buntmetallen kommen in Stufe II vor. Gold-Silber-Telluride (Krennerit, Petzit, Sylvanit und möglicherweise die seltene X-Phase) sind in Stufe III ausgebildet und in Stufe IV wurden Baryt, Flusspat, Dolomit, Magnesit, Spuren von Kaolin und Serizit gebildet. Unter Verwendung der Mineralassoziationen der Stufe Ib lassen sich Werte von logf Te₂ zwischen - 10.5 und - 9.7 und von logf S₂ zwischen - 12.6 und - 5.5 errechnen.[Die erzbildenden Komponenten (z.B. Au, Ag, Te, Cu, Bi, Mo und der Grossteil von S) stammen wahrscheinlich vom Intrusivsystem aus der Oberkreide, möglicherweise mit Beiträgen der proterozoischen Umgebung.[/ p]

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With 10 Figures     

Mineral systems,their types,and distribution in nature. I. Khibiny,Lovozero, and the Mont Saint-Hilaire

In accordance with the set of species-defining chemical elements in minerals, n-component systems (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10) for all mineral species (4952) known to 2014 inclusive were distinguished. Seventy chemical elements have been established to be species-defining, which are distributed by mineral systems as follows: 1 (29), 2 (62), 3 (68), 4 (61), 5 (61), 6 (55), 7 (49), 8 (38), 9 (28), and 10 (19). The number of mineral species in which certain chemical elements are species-defining has been specified. Oxygen (4041), hydrogen (2755), silicon (1448), calcium (1139), sulfur (1025), aluminum (960), iron (917), sodium (914), copper (616), phosphorous (580), arsenic (575), and magnesium (550) are the leading elements in minerals in the Earth’s crust. It has been found that the most species-defining elements are normally distributed by mineral systems. The distributions of mineral species in various systems from the Khibiny and Lovozero, Kola Peninsula, Russia; and Mont Saint-Hilaire, Quebec, Canada peralkaline plutons were compared and the characters of species-defining element distribution in these localities were compared. Si, Na, K, C, F, Ti, Ce, Zr, Nb, Sr, and Th are “excess” species-defining elements in minerals from the plutons compared to the total number of mineral species, whereas S, Cu, Pb, Cl, B, Te, Ag, Ni, and Be are “scarce” elements.     

Groundwater transport of arsenic and chromium at a historical tannery,Woburn, Massachusetts,U.S.A.

The geochemical environment in hide piles at a historical tanning and rendering site (Woburn, Massachusetts, U.S.A.) is strongly reducing, as reflected by the presence of H₂S and CH₃HS in the pile offgas. The presence of a reducing environment in the Subjacent groundwater, along with DOC (≥ 100mg/l) from hide breakdown, results in reduction of As(V) to As(III), and subsequent methylation to monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). The reducing conditions also result in precipitation of FeS_(am), while hydrophilic organic acids have increased Cr(III) solubility. Three spatially sequential geochemical redox facies were recognized in groundwater downgradient from the hide piles. Typically, a reduced core zone was present adjacent to the hide piles, characterized by S²⁻ ≥ 1mg/l, Fe²⁺ <5mg/l,NH₃ ≥ 200mg/l and the presence of MMAA in conjunction with DOC (−30mg/l). This facies transitions through an intermediate zone, represented by Fe²⁺ > 20mg/l, NH₃ (5–200 mg/l) and the sporadic presence of measurable S²⁻ (1–2 mg/l), to an oxidizing peripheral zone characterized by conditions representative of background (i.e. DO> 1mg/l, Eh> 0mV, Fe²⁺ < 20mg/l, S²⁻ < 1mg/l,NH₃ < 5mg/l and NO₃⁻ >NH₃), accompanied by precipitation of amorphous ferric hydroxide, sorption of As and co-precipitation-sorption of Cu, Pb and Zn. Electron microprobe analysis of hide-pile materials demonstrated authigenic precipitation of amorphous ferric hydroxide and gypsum, in agreement with the results of geochemical modeling.     

Hydrogeochemical exploration for Mississippi valley-type deposits, Arkansas, U.S.A.

Three areas located in northern Arkansas, U.S.A., representing differing host rock and mineralization, were selected to investigate the usefulness of hydrogeochemical exploration for Mississippi Valley-type Pb-Zn mineralization. Despite the geologic differences among the areas, there were no great differences in groundwater chemistry and threshold values. Anomalous Pb concentrations, and also anomalous Zn concentrations to a lesser extent, are useful in detecting the Pb-Zn mineralized areas; however, specific deposits could not be located. Because of the low threshold values (about 20 μg/1) for Pb and Zn, spring water must be utilized in order to avoid plumbing contamination.