关于岩石风化过程中化学组分迁移的定量研究方法

岩石化学分析结果的定和效应给定量研究风化体系中化学组分的迁移规律带来困难。一般岩石风化体系可以有母岩-滤液和母岩-风化产物两个子体系。本文即探讨该二子体系中化学组分迁移的定量计算问题。对比分析表明,母岩-滤液子体系方法较适用于风化程度高的体系,而母岩-风化产物子体系方法较适用于风化程度低的体系。对于风化程度中等的体系,宜采用两种子体系方法所得结果的加权平均,其中权重按风化程度取值。     

A survey of the age relations of Shetland Rocks

The survey is based on field work by Flinn, on forty-two K-Ar age determinations by Miller, and on previously published work on Shetland. Most of the metamorphic rocks give K-Ar ages of about 420 m.y. It is clear from petrological and stratigraphical evidence that this age is not the age of the metamorphisms and migmatizations responsible for the more obvious features of the rocks, and also that the metamorphic rocks in different areas have had different histories of development. Ages up to 515 m.y. have been found in various areas, and these may be more closely related to the main metamorphisms than the more common 420 m.y. ages. In the Mainland the 420 m.y. age may be related to a late porphyroblast metamorphism: in Unst and Fetlar it seems to be the age of Read's second metamorphism which accompanied the emplacement of nappes and the formation of orogenic sediments. About 400 m.y. ago a series of postorogenic granitic and appinitic complexes were emplaced in the southern part of Shetland. By 380 m.y. ago erosion had reached migmatitic rocks and they were being buried again beneath Old Red sediments and contemporaneous volcanics. Later still, possibly 350 m.y. ago, in Upper Devonian times, granites were emplaced in the west of Shetland cutting the Old Red rocks. Finally the Walls Boundary Fault (Great Glen Fault ?) cut one of these late granites.     

弓长岭铁矿蚀变岩及富矿成因

弓长岭铁矿床是鞍山本溪地区最典型的BIF型铁矿床之一,而且是该地区最大的富铁矿产区。从野外产出关系来看,弓长岭矿区的富铁矿与蚀变岩密切相关,蚀变岩与富铁矿基本上是形影相随。蚀变岩具有分带性,由富铁矿向外依次为镁铁闪石岩石榴石岩绿泥石岩弱蚀变斜长角闪岩斜长角闪岩。弱蚀变岩保留了蚀变原岩的岩貌特征,矿物的蚀变并不完全,可见残余的原生矿物。强蚀变岩的蚀变较彻底,基本无原生矿物残留。将蚀变岩与斜长角闪岩、磁铁石英岩的地球化学特征进行对比可以发现弱蚀变岩、石榴石岩、绿泥石岩与斜长角闪岩的痕量元素特征基本一致,而镁铁闪石岩的痕量元素特征更接近磁铁石英岩。再结合镜下特征、野外接触关系、主量元素特征等证据,认为除了镁铁闪石岩是由磁铁石英岩蚀变形成,其余蚀变岩都是由斜长角闪岩蚀变形成。根据各类蚀变岩中主要矿物的(Fe+Mg)/Si值以及蚀变岩的SiO2和Fe2OT3含量变化规律可以发现,在蚀变岩和富矿形成过程中发生了Mg、Fe以及Si的迁移。对本次取样的样品进行原岩恢复和构造环境判别投图,投图结果表明,绿泥石岩和弱蚀变岩的最初原岩都是形成于弧后盆地的玄武岩。     

Accelerated aqueous leaching of selenium and arsenic from coal associated rock samples with selenium speciation using ultrasound extraction

Ultrasound extraction was used to compare the accelerated release rates of selenium and arsenic from three rocks (BT700, BT 571 and BT 60) that are associated with mountaintop mining and valley fill coal mining practiced in southern parts of West Virginia, USA. The concentrations of arsenic released from rocks were found to be three orders of magnitude higher than that of selenium. The accelerated leaching rate constants were ten times higher for arsenic compared to selenium. Se (IV) was found to be stable under ultrasound extraction conditions used whereas As (III) was quickly oxidized to As (V). BT700 was found to have more Se (IV) compared to BT571 while BT60 did not have any significant Se (IV) concentrations. Such compositional and kinetic information becomes important when determining suitable mining waste treatment protocols that have to be undertaken to different types of overburden before it is dumped in valleys.     

鄂尔多斯盆地三叠系延长组长7段物源区分析

随着鄂尔多斯盆地长7段油藏勘探的不断突破,对其物源方向和母岩区性质的分析尤显重要.三叠世延长期鄂尔多斯盆地周缘存在多个古陆,包括北缘的阴山古陆、西北缘的阿拉善古陆、西南缘的陇西古陆及南缘的祁连-秦岭古陆等,它们都是盆地碎屑沉积物的主要供给源.通过碎屑组分、岩屑组分、重矿物、微量元素和稀土元素分析等研究,认为研究区长7段存在东北、西北、西及西南、南部4个方向的物源.轻、重矿物组合综合分析认为,盆地北部母岩主要为太古宙—古生代中—深变质岩和中基性火成岩,西南及南部母岩主要为元古宙—古生代浅变质岩、碳酸盐岩和碎屑岩.微量及稀土元素分析表明母岩以大陆上地壳的长英质岩石为主,并混有一定数量的含长石较高的中—基性岩浆岩如安山岩、碱性玄武岩,母岩中太古代古老地层占有相当大的比重.     

中国北方烧变岩的分布、特征及研究意义*

中国北方烧变岩分布广泛,见于以昆仑山—秦岭—大别山为界的中国北方地区多个沉积盆地边缘,但地质学家对其研究较为薄弱。野外调查显示中国北方烧变岩主要以4种方式分布: (1)大面积连片分布,(2)沿山脉走向的线状分布,(3)沿河流下切河谷分布,(4)为第四系黄土覆盖。烧变岩主要为侏罗系、石炭—二叠系煤层自燃所致。各类型的烧变岩在中国烧变岩区不同程度发育,具瓷化结构、白化结构、烧熔结构、残余构造、气孔构造、微柱状节理、角砾状构造、垮塌构造、裂缝充填等结构和构造。其颜色以砖红色、赭红色、棕色、钢灰色最为典型,岩石中发育鳞石英、方石英、堇青石、铁堇青石、莫来石等典型高温矿物。中新世以来,中国西部、北部地区构造活动强烈,干旱气候加剧,烧变岩也主要形成于这一时期,但煤层自燃与构造运动、环境变化、古野火事件的耦合关系还鲜有提及,其所蕴含的各种地质信息值得在今后的研究中予以关注。     

Magnetite/Ilmenite–series Classification and Magnetic Susceptibility of the Mesozoic-Cenozoic Batholiths in Peru

Abstract: Plutonic rocks of the Coastal Batholith of Peru were evaluated in terms of the granitoid-series classification using the bulk ferric/ferrous ratio from the literature and new measurements of magnetic susceptibility. The batholith is largely composed of magnetite-series plutonic rocks; the magnetite series make up 85% by number of chemical analyses (n=130) and 80% by measurement of magnetic susceptibility (n=210). The ilmenite-series rocks are mostly found in the felsic facies of the batholith. Asymmetrical distribution of magnetic susceptibility is not clear as in the Japanese Islands and Peninsular Range Batholith, but the magnetic susceptibility may decreases continentward (i. e., Peninsular Range type).
The Cordillera Blanca Batholith and stocks are also composed of mainly magnetite series plutonic rocks, but ilmenite-series rocks may be more predominant than in the Coastal Batholith, which is also indicated by the presence of Sn and W mineralizations.     

大桥坞产铀火山-侵入杂岩的岩浆混合作用及其对赣杭构造带铀成矿潜力的指示意义

浙江省大桥坞铀矿床赋矿围岩为一套火山-侵入杂岩,锆石U-Pb定年显示该套杂岩的成岩时代为138~125 Ma。Hf同位素分析结果显示随着成岩时代变新,这些岩石中锆石εHf(t)值从约-13.0升高到约-3.0。锆石饱和温度同样表现出升高的趋势,从~749℃升高到~846℃。以上特征表明大桥坞地区火山-侵入杂岩为壳幔岩浆混合成因,且幔源物质加入的比例随成岩时代变新而增多。综合前人对赣杭构造带相山、芙蓉山和沐尘地区花岗质岩石的研究结果,发现这些岩石的全岩εNd(t)值和锆石εHf(t)值在135~112 Ma期间分别从-9.0升高到-2.0和-10.0升高到2.0,表明其成因上可能同壳幔岩浆混合有关,且随着成岩时代变新幔源岩浆的加入逐渐增多。Sr-Nd同位素模拟显示幔源岩浆加入的比例在135~112 Ma期间从0升高到~60%。由于幔源岩浆较壳源岩浆贫U和Th,前者的加入会稀释壳源岩浆中U和Th的含量,降低其铀成矿潜力。幔源物质加入越多,铀成矿潜力越低。赣杭构造带壳幔岩浆混合作用呈西弱东强的地质事实,可能是该带上铀矿床的分布呈西大东小格局的重要原因之一。因此,赣杭构造带东段找矿需关注富铀基底(花岗岩或长英质变质岩基底)与早白垩世火山岩盖层相结合的地区。     

塔里木盆地哈拉哈塘凹陷东西两侧海相稠油地球化学特征：以LG7井和DH1-6-9井稠油为例

塔里木盆地哈拉哈塘凹陷东侧轮古地区有丰富的海相稠油产出,其中包括大型的塔河油田群,在凹陷的西北缘也有海相稠油发现。凹陷东侧海相稠油的地球化学成因已经有较多的研究报道,而西北缘针对海相稠油的研究工作仍然十分薄弱,其地球化学成因仍需深入探讨。本工作以哈拉哈塘凹陷东西两侧的稠油LG7井和DH1－6－9井为例,对比研究其地球化学特征,重点对比分析稠油沥青质中吸附／包裹烃类化合物的地球化学应用。研究结果表明凹陷东西两侧的稠油藏至少经历了两期油气的充注,其中第一期充注来自同一套烃源岩,后期遭受了,严重的生物降解改造;第二期充注来自另一套烃源岩,其正构烷烃仍然具有完整的分布模式。凹陷两侧稠油经历了相似的后期成藏过程,在西北缘相应的构造单元中可望发现更多海相来源的油气资源。     

内蒙古西部额济纳旗及邻区上石炭统—下二叠统 阿木山组的沉积特征和时代

额济纳旗地区是阿木山组分布的最西端,产出于伸展背景下的裂谷环境,火山岩比较发育,从下到上可分为火山岩段、灰岩段和碎屑岩段。火山岩段和灰岩段产丰富 的 类化石,灰岩段下部产丰富的珊瑚化石。珊瑚化石的时代主要为晚石炭世, 类从下到上分别属于Triticites组合和Pseudoschwagerina组合,从而确定阿木山组的3个岩性段之间以叠覆关系为主,地质时代为晚石炭世至早二叠世,其中火山岩段为晚石炭世小独山期或更早;灰岩段下部为小独山期,上部为紫松期;碎屑岩段为早二叠世紫松期或更晚一些至隆林期。     

Geochemistry of igneous rocks associated with ultramafic–mafic-hosted Cu (Co, Ni, Au) VMS deposits from the Main Uralian Fault (Southern Urals, Russia)

Ultramafic–mafic- and ultramafic-hosted Cu (Co, Ni, Au) volcanogenic massive sulfide (VMS) deposits from ophiolite complexes of the Main Uralian Fault, Southern Urals, are associated with island arc-type igneous rocks. Trace element analyses show that these rocks are geochemically analogous to Early Devonian boninitic and island arc tholeiitic rocks found at the base of the adjacent Magnitogorsk volcanic arc system, while they are distinguished both from earlier, pre-subduction volcanic rocks and from later volcanic products that were erupted in progressively more internal arc settings. The correlation between the sulfide host-rocks and the earliest volcanic units of the Magnitogorsk arc suggests a connection between VMS formation and infant subduction-driven intraoceanic magmatism.     

AGE OF ALKALINE-ULTRABASIC ROCKS OF MAYMECHA-KOTUY REGION ACCORDING TO PALEOMAGNETIC DATA

Investigations of widely distributed negative magnetic anomaties in the Maymecha-Kotuy region (72° N. Latitude, 102° E. Longitude), showed that remanent magnetization is present in the rocks; and, that they could be subdivided into magnetically stable and unstable categories. Studies were based on 1,600 oriented rock samples. Paleomagnetic data derived from mean directions of magnetization were used to calculate the North Polar coordinates for the time of formation for the various rocks; these data can be compared to mean values of North Polar coordinates determined for various periods. Mean values for the North Polar coordinates derived from remanent magnetization data on basic and ultrabasic rocks of the Maymecha-Kotuy region, correspond to those of Permian-Carboniferous time. No paleomagnetic age correlation was possible for magnetically unstable rocks. Results disagree with paleontological data, which indicates these rocks to have formed in late Permian to Early Triassic times; however, they are found to agree with data derived by the argon method. A correction of 20° mean value of dip in meymechites, was incorporated into the calculations with the result that the corresponding polar coordinates were 44° N. Latitude, 148° E. Longitude; and, in agreement with findings for all other rocks. Thus, meymechites probably were formed as a horizontal layer and, later, uplifted by younger intrusion of dunite-peridotite magma; and, that they are probably of effusive origin. It is believed that this method can be used eventually for more extensive determination of age correlation for various rocks and massifs. --D. D. Fisher.     

北疆吉木乃布氏金矿幔源岩浆岩时代及Sr、Nd同位素证据

位于斋桑地洼区萨吾尔山北坡的布氏金矿是＂七五＂期间新发现的一个矿床。本文通过对区内典型火山岩、侵入岩体的岩石地球化学特征及锶、钕同位素的研究，确定它们形成于晚古生代，火山岩的喷发年龄为３４７Ｍａ，侵入岩的定位年龄为３１０～３２９Ｍａ；同位素特征参数＝０．７０３７～０．７０４６，都比较小，值为＋６．６７～－５．５６，近于零，值为＋５．６５～＋７．９６，大于零，说明它们具有相似的物质来源，是地幔岩浆或其衍生物熔融导生的；斋桑地洼区的基底为晚元古代甚至更老，地壳的增生可能是遵循非均一的生长模式。     

塔里木盆地阿克库勒凸起卡拉沙依组储层特征研究

阿克库勒凸起石炭系卡拉沙依组碎屑岩储层中,长石的含量大于岩屑的含量,储集层成分成熟度和结构成熟度均较低,颗粒之间多呈点-线接触.胶结类型为孔隙式,主要为碳酸盐岩胶结.虽然早期碳酸盐岩胶结降低了砂岩的原始孔隙度和渗透率,但也为次生孔隙的形成提供了物质基础.该组储集层中次生孔隙的含量远大于原生孔隙.从压汞资料上可以看出,孔喉分布不均,但呈粗歪度,储层孔渗性均较低,属中低孔,低渗的储层.该组成岩作用已达到晚成岩A期,早期方解石交代石英颗粒并发生大量溶蚀,生成大量次生孔隙;晚期方解石没有发生溶蚀,但交代早期方解石和各种自生粘土矿物.     

三论花岗岩按照Sr-Yb的分类:应用

在"再论"中我们提出了花岗岩按照Sr-Yb分类的新标志(张旗等,2010a),本文进一步讨论该分类的应用。文中举了国内外许多实例(包括柴达木、北祁连、内蒙古、松潘-甘孜、大别、太行、华北古元古代和华南新元古代以及土耳其、俄罗斯、巴西、刚果、波西米亚、意大利等),着重讨论了花岗岩Sr和Yb含量与其形成压力和深度的关系,指出本分类最重要的地球动力学意义在于与其形成的深度有关,并在一定条件下与其产出地区的地壳厚度有关。例如应用本方法分析华北克拉通古元古代花岗岩,很难得出该带在古元古代发生过碰撞的结论,华北克拉通是否分为东西两块也需要重新认识。又如对华南新元古代花岗岩的分析表明,华南地块内部在新元古代时地壳较薄,但是,与Rodinia大陆的裂解似乎无关。文中还对花岗岩与成矿的关系进行了讨论,提出成矿与压力有关的概念。如金铜与地壳厚度大的埃达克型和喜马拉雅型花岗岩有关,钨锡与地壳厚度薄的南岭型花岗岩有关,而不论矿床是什么类型的,只要它们与花岗岩有关,必定受矿液源区深度的控制,要么是在加厚地壳的地球动力学背景下,要么是在地壳减薄的地球动力学背景下。花岗岩无比复杂,我们用Sr和Yb两个元素对花岗岩重新进行了分类,只是一个探索性的尝试,问题肯定不少,需要广泛的实践的检验,需要深入的实验研究的检验,需要理论的探讨,需要经过一系列否定-肯定-否定的过程,才能逐渐臻于完善。     

不同类型沉积物中脂肪酸的分布、演化和生烃意义

对近代海洋沉积物、泥炭、福山凹陷第三系泥岩、茂名盆地第三系油页岩和辽河盆地东部凹陷第三系沉积岩剖面等样品中脂肪酸类型和分布特征进行了分析与研究。结果表明以低等浮游动植物为主的沉积中，二元肪酸丰度相对比一元酸占优势。随深程度增加，沥青中脂肪酸高碳数相对减少，低碳数相对增高，偶碳估势逐渐消失。在辽河盆地东部凹陷埋深２２６６ｍ的泥岩中发现脂肪酸仍具有偶碳优势，证明沉积有机质中偶碳脂肪酸优势可以保存到生油高峰前的较高演化阶段，对低熟原油烷烃的生成和具奇碳优势有重要意义。     

中国超高压变质岩十五年研究进展

本文对20世纪80年代以来中国超高压变质岩研究的历史做了简要回顾，列举了该领域的5项重要进展，即：①发现了大批超高压变质岩，使中国的大别山-苏鲁超高压变质岩带成为世界之最；②通过细致的矿物学研究，确认低密度的陆壳岩石可以被俯冲到地下200多公里深处，经历超高压变质作用；③多种同位素体系定年结果表明，大别山-苏鲁超高压变质作用是在中生代早期扬子板块俯冲到中朝板块之下时发生的；④对超高压变质岩中O、C、H等同位素的研究进一步表明，超高压变质作用过程中并无大规模流体活动，大气水的O同位素成分可被带到地幔深处而不改变；⑤通过对岩石学、矿物学、年代学、构造地质学、地球物理学等多学科资料的综合研究，提出了超高压变质地体的多阶段折返模式。文中对目前超高压变质岩研究中的几个争论焦点做了归纳。     

Using whole rock geochemistry to locate the source of igneous erratics from drumlins on the Atlantic coast of Nova Scotia

Whole rock geochemistry has been determined for erratics from the surface Lawrencetown Till in two drumlins on the Atlantic coast of Nova Scotia. The geochemical data, particularly trace element composition, allow source rocks to be identified more precisely than by traditional petrographic microscopy. A drumlin near Lunenburg contains erratics of Neoproterozoic arc-related plutonic rocks and basalts that outcrop only in a small area near Parrsboro in the Cobequid Highlands. Some associated erratics of granite precisely match a small late Devonian pluton in the same area and other granites and rhyolite could also be derived from late Devonian rocks in the same area. The type section of the Lawrencetown Till contains different Neoproterozoic plutonic rocks of a type found in the eastern Cobequid Highlands, together with a distinctive late Devonian granite with sodic amphiboles that is restricted to a small area near the Debert River. Both these source areas indicate a southward flow of ice (Escuminac Phase) depositing the Lawrencetown Till, in contrast to earlier southeastward-flowing ice (Caledonia Phase) which deposited the Hartlen Till that forms the core of the drumlin. Drumlins in Nova Scotia are complex palimpsest landforms that were formed by till accretion, and evolved in surface form throughout multiple flow events.     

Chemical analyses of Bosumtwi crater target rocks compared with the Ivory Coast tektites

The Bosumtwi crater, Ghana, was excavated in phyllites and greywackes with subordinate microgranite dykes and quartz veins of the 2000 Ma old Lower Birimian System with a granodiorite intrusion at Pepiakese on its northeastern side. New major and trace element analyses are presented for 7 phyllites, 5 greywackes, 2 microgranites, 3 Pepiakese intrusion rocks and 1 suevite using XRF and INNA.Means and standard deviations were calculated using all available modern analyses for each element in the Bosumtwi target rocks, Bosumtwi suevite glasses and Ivory Coast tektites. Good agreements between the means were found for the three groups with the suevite glasses and tektites having more limited compositional ranges than the target rocks. Least squares mixing between target rock types shows that the best fits to the tektite and suevite glass compositions require components of about a third or a quarter from the Pepiakese intrusion and some extra silica, derived from quartz veins, as well as the metasediments.The new data provide evidence for vapour phase fractionation of P₂O₅ and Na₂O in the tektites in addition to the previously reported Pb and Rb. Evidence for a meteoritic component in the tektites was found to be equivocal since the target rocks are probably a sufficient source of the meteorite indicator elements Ni and Ir.     

Protoliths of the 3.8–3.7 Ga Isua greenstone belt,West Greenland

The Isua greenstone belt (Fig. 1) contains the oldest known, relatively well preserved, metavolcanic and metasedimentary rocks on Earth. The rocks are all deformed and many were substantially altered by metasomatism, but both the deformation and metasomatism were heterogeneous. Transitional stages can be seen from relatively well preserved primary volcanic and sedimentary structures to schists in which all primary features have been obliterated. Likewise different kinds, and different episodes, of metasomatic alteration can be seen that produced a diversity of different compositions and metamorphic mineral assemblages from similar protoliths. New geological mapping has traced out gradations between the best preserved protoliths and their diverse deformed and metasomatised equivalents. By this means, the primary nature of the schists that make up most of the Isua greenstone belt was reinterpreted, and a new map that better portrays the primary nature of the rocks has been produced. The previously mapped stratigraphy was found to be of little value in understanding the geology. Stratigraphic units were defined by different and diverse criteria, such as current composition, structure, metamorphic texture, and inferred protoliths. Much of this stratigraphy represents a misinterpretation of the primary nature of the rocks. The new work indicates that most of the Isua greenstone belt consists of fault-bounded rock packages, mainly derived from basaltic and high-Mg basaltic pillow lava and pillow lava breccia, chert–BIF, and a minor component of clastic sedimentary rocks derived from chert and basaltic volcanic rocks. A previously mapped, extensive, unit of felsic volcanic rocks was found to be derived from metasomatised basaltic pillow lava and pillow breccia intruded by numerous sheets of tonalite.