华南早寒武世黑色岩系镍钼多金属矿床矿物学特征研究

湖南张家界三岔和贵州遵义黄家湾在下寒武统黑色岩系中发育有镍钼多金属矿床,这是华南乃至全球这类矿床的2个典型实例。通过对其进行系统的矿相显微镜、电子探针以及扫描电子显微镜观测分析,分析了成矿岩系的矿物学特征,并进一步根据矿物结构、组成与共生关系,结合地质背景,讨论了矿床成因。结果显示,非矿层中的金属矿物类型较为单一,主要是黄铁矿;而矿层中发现的矿物种类丰富,主要包括＂碳硫钼矿＂、针镍矿、黄铁矿、胶磷矿等,其中＂碳硫钼矿＂和针镍矿分别是钼与镍的主要赋存形式。认为钼主要来自于海水,镍主要来自于热水（液）流体,矿床为海水-热水（液）-生物复合成因。这些研究结果为此类矿床研究提供了新的矿物学基础研究资料,并且有助于加深对矿床成因的认识。     

湘西北下寒武统镍-钼多金属富集层镍与钼的赋存状态

对湘西北三岔、杆子坪镍-钼富集层中镍-钼矿石进行了电子探针研究,发现了镍黄铁矿、辉砷镍矿、方硫镍矿、针镍矿、紫硫镍矿与铁辉砷镍矿等镍的独立矿物与“碳硫钼矿”等含钼的矿物。研究表明,镍-钼富集层中镍主要赋存在上述含镍矿物及细粒胶状黄铁矿中;钼主要以“碳硫钼矿”的形式存在。     

遵义黄家湾镍钼多金属矿成矿特征与成因

贵州遵义地区黄家湾镍钼多金属矿是寒武系底部的黑色页岩型矿床。黑色岩系中微量元素特征显示镍钼多金属矿层的Ni,Mo,Cd,V,Cu,Zn明显富集,而高场强元素Nb,Th,Hf,Zr,Ti亏损。稀土元素显示多金属矿层的艿（Eu）呈正异常,中稀土富集,重稀土亏损。结合镜下观察发现的有机质、红藻囊果与金属硫化物之间密切的共生关系和前人研究结果,分析了黑色岩系镍钼多金属矿的成因,认为镍、钼、铜、锌等金属元素的来源与热液有关,通过生物作用聚集并在缺氧的还原沉积环境下大量堆积,富集形成Ni—Mo金属硫化物矿床。     

New Evidence for Hydrothermal Sedimentary Genesis of the Ni‐Mo Deposits in Black Rock Series of the Basal Cambrian,Guizhou Province: Discovery of Coarse‐Grained Limestones and its Geochemical Characteristics

The molybdenum-nickel deposits in Shuidong District of Nayong County (Guizhou Province, Southwest China) are found mainly in black shale series of Lower Cambrian Niutitang Formation, which is another Mo-Ni-rich region besides Zunyi District (Guizhou province). Our systematic study on the Mo-Ni deposits in Tangjiaba of Nayong reveals that layered coarse-grained limestones, spherical beaded limestones concretions are hosted at the lower seam of the Mo-Ni deposits. Its strong negative carbon isotope anomaly (the carbon isotope value of the coarse-grained limestones varies from ?2.148‰ to 8.223‰) is similar to that in the modern submarine black smoker chimney. The carbon in the coarse-grained limestones from black rock series of Nayong County might be deep source inorganic carbon. The seams, coarse-grained limestones, ore-bearing coarse-grained limestones and the roof and floor of the deposits are characterized by co-variation on the trace element spider diagram, showing good homology. The extraordinary enrichment of Ag, As and Sb resembles hydrothermal sedimentation. Pro-Earth's core elements Se is strongly enriched in Ni-Mo ore-bearing coarse-grained limestones. The ore-bearing rock series has an extremely low Th/U value (0.012–0.19); in the logU-logTh Cartesian Coordinates, the samples of the roof and floor of the deposits and ore-bearing coarse-grained limestones are found in the East Pacific tise; and the samples of coarse-grained limestones are found between the paleo-hydrothermal dedimentary area and the East Pacific tise. The chondrite-normalized rare earth element patterns of the Ni-Mo deposits show LREE enrichment, Ce negative anomaly, and Eu negative anomaly (which is supposed to be influenced by the deep magmatic processes in an extensional environment) resembles the rare earth element distribution patterns of the fluid and its sediments in modern submarine hydrothermal system. It proves that coarse-grained limestones is characterized by typical hydrothermal limestones, being closely related with the genesis of Mo-Ni deposits in Nayong County, which provides new evidence for hydrothermal sedimentary genesis of Mo-Ni deposit and negative carbon anomaly in the basal Cambrian on a global scale.     

芬兰北部克维特斯塔镍-铜-铂族元素矿床地质特征及矿床成因

位于芬兰北部中拉普兰绿岩带的克维特斯塔(Kevitsa)镍-铜-铂族元素矿床是世界上主要的岩浆镍-铜硫化物矿床之一。该矿床储量大,含丰富的镍-铜硫化物和铂族元素。对矿床产出环境、地质特征、矿床成因等进行了总结,结果表明:矿体主要赋存于克维特斯塔基性—超基性层状侵入体的超基性单元中。主要矿石类型为普通型和镍-铂族元素型2种,其中镍-铂族元素型矿石内橄榄石具极高的Ni含量。主要矿石矿物为磁黄铁矿、镍黄铁矿、黄铜矿、黄铁矿、针硫镍矿、红砷镍矿、砷镍矿、辉砷镍矿等,绝大部分铂族矿物包含在硅酸盐中和附着在硫化物颗粒边界。Re-Os、Sm-Nd、Sr及S同位素特征显示成矿岩浆为幔源,但受到地壳物质的混染作用。Pb同位素年代学结果表明克维特斯塔侵入体形成于古元古代。     

Chemistry and Sulfur Isotopes in a Chert-dominant Sequence around the Stratiform Manganese Deposit of the Noda-Tamagawa Mine, Northern Kitakami Terrane, Northeast Japan: Implication for Paleoceanographic Environmental Setting

Abstract. Chemistry and sulfur isotopes are analyzed for a series of rocks in the chert‐dominant sequence around the stratiform manganese ore deposit of the Noda‐Tamagawa mine in the northern Kitakami Terrane, northeast Japan. The sequence is litholog‐ically classified into six units in ascending order: lower bedded chert, lower black shale, massive chert, manganese ore, upper black shale, and upper bedded chert. The rocks around the manganese ore deposit exhibit anomalous enrichment in Ni (max. 337 ppm), Zn (102) and U (30) in the upper part of lower bedded chert, Mo (122), Tl (79) and Pb (33) in the lower black shale, MnO, Cu (786) and Co (62) in the manganese ore, and As (247) and Sb (17) in the upper black shale. The aluminum‐normalized profiles reveal zonal enrichment of redox‐sensitive elements around the manganese bed: Zn‐Ni‐Fe‐Mo‐U(‐Co), Tl‐Pb(‐Mo), Mn‐Fe‐Cu‐V‐Cr‐Co(‐Zn) and As‐Sb in ascending order. The uppermost part of the lower bedded chert and black shale exhibit negative Ce/Ce* values, whereas the massive chert, manganese ore and lower part of the upper bedded chert display positive values. The isotopic δ³⁴S values are 0±6 % in the lower part of the lower bedded chert, ‐19 to ‐42 % in the upper part of the lower bedded chert, ‐36 to ‐42 % in the lower black shale, ‐28 to ‐35 % in the massive chert, manganese ore and upper black shale, and ‐23±5 % in the upper bedded chert. Thus, there is a marked negative shift in δ³⁴S values in the lower bedded chert, and an upward‐increasing trend in δ³⁴S through the manganese ore horizon. The present data provide evidence for a change in the paleoceanographic environmental resulting from inflow of oxic deepwater into the stagnant anoxic ocean floor below the manganese ore horizon. This event is likely to have triggered the precipitation of manganese oxyhydroxides. The redistribution of redox‐sensitive elements through the formation of metalliferous black shale and manganese carbonate ore may have occurred in association with bacterial decomposition of organic matter during early diagenesis of initial manganese oxyhydroxides.     

芬兰北部克维特斯塔镍-铜-铂族元素矿床地质特征及矿床成因

位于芬兰北部中拉普兰绿岩带的克维特斯塔(Kevitsa)镍-铜-铂族元素矿床是世界上主要的岩浆镍-铜硫化物矿床之一。该矿床储量大,含丰富的镍-铜硫化物和铂族元素。对矿床产出环境、地质特征、矿床成因等进行了总结,结果表明：矿体主要赋存于克维特斯塔基性—超基性层状侵入体的超基性单元中。主要矿石类型为普通型和镍-铂族元素型2种,其中镍-铂族元素型矿石内橄榄石具极高的Ni含量。主要矿石矿物为磁黄铁矿、镍黄铁矿、黄铜矿、黄铁矿、针硫镍矿、红砷镍矿、砷镍矿、辉砷镍矿等,绝大部分铂族矿物包含在硅酸盐中和附着在硫化物颗粒边界。Re-Os、Sm-Nd、Sr及S同位素特征显示成矿岩浆为幔源,但受到地壳物质的混染作用。Pb同位素年代学结果表明克维特斯塔侵入体形成于古元古代。     

延边三岔钼矿床地质特征及找矿方向

三岔钼矿床为斑岩型钼矿床,是该区主要矿床工业类型.通过该矿床地质特征的论述,初步分析了矿床的成因,提出了该区找矿方向及找矿标志.     

Multiple Sources of Metals of Mineralization in Lower Cambrian Black Shales of South China: Evidence from Geochemical and Petrographic Study

Black shales of the Lower Cambrian Niutitang Formation in southern China (Huangjiawan mine, Zunyi region, northern part of the Guizhou Province) host regionally distributed stratiform polymetallic Ni‐Mo‐platinum group elements (PGE)‐Au phosphate‐ and sulfide‐rich ores. These are confined to a ≥0.2‐m thick ore horizon composed of mineralized bodies of algal onkolites, phosphate nodules, and sulfide and shale clasts in a mineralized phosphate‐ and organic matter‐rich matrix. Compared to footwall and hanging wall shales, the ore bed is strongly enriched in Ni (up to 100‐fold), As (up to 97‐fold), Mo (up to 95‐fold), Sb (up to 67‐fold), Rh (up to 49‐fold), Cu (up to 37‐fold), Pd (up to 33‐fold), Ru (up to 24‐fold), Zn (up to 23‐fold), Pt (up to 21‐fold), Ir (up to 15‐fold), Co (up to 14‐fold), and Pb (up to 13‐fold). Even footwall and hanging wall black shales are significantly enriched by Mo (21‐fold) and Ni (12‐fold) but depleted in Cr in comparison to average Cambrian black shale. Organic matter is represented by separate accumulations dispersed in the rock matrix or as biotic bitumen droplets and veinlets in ore clasts. Similar organic carbon (C_org) values in an ore bed and enclosing footwall and hanging wall shales of little mineralization indicate that metal accumulation was not controlled only by biogenic productivity and organic matter accumulation rate. Evaporitic conditions during sedimentation of the basal part of the Niutitang Formation were documented by an occurrence of preserved Ni‐, V‐, Cr‐, and Cu‐enriched phosphate‐rich hardground with halite and anhydrite pseudomorphs on the paleosurface of the underlying Neoproterozoic carbonates. Neoproterozoic black shales of the Doushantuo Formation are characterized by increased metal concentrations. Comparison of metal abundances in both hardground and Doushantuo black shales indicate that black shales could have become a source of metal‐rich hardground during weathering. The polymetallic Ni‐Mo‐PGE sulfide‐rich ore bed is interpreted to represent a remnant of shallow‐water hardground horizon rich in metals, which originated in a sediment‐starved, semi‐restricted, seawater environment. During the Early Cambrian transgression an influx of fresh seawater and intensive evaporation, together with the hydrothermal enrichment of seawater in a semi‐restricted basin, resulted in the formation of dense metalliferous brines; co‐precipitation of metals together with phosphates and sulfides occurred at or above the oxic–anoxic sediment interface. Metal‐enriched hardground was disintegrated by the action of waves or bottom currents and deposited in a deeper part of the anoxic basin. Contemporaneously with the formation of a polymetallic Ni‐Mo‐PGE‐Au sulfide ore bed, economic sedimentary exhalative (SEDEX)‐type barite deposits were forming in a stratigraphically and geotectonically similar setting. The results of geochemical study at the Shang Gongtang SEDEX‐type Ba deposit indicate that concentrations of Ag, As, Cr, Cu, Fe, Mn, Ni, Pb, Sb, V, Zn and other metals decrease from top of the barite body toward the hanging wall black shale. Lower Cambrian black shales of the Niutitang Formation above the barite body also display similar element abundances as Neoproterozoic black shales of the Doushantuo Formation, developed in the footwall of the barite body. But the geochemical composition of the sulfide layer is different from the Ni‐Mo ore bed, showing only elevated Pb, Cu, Ni and Mo values. It is suggested that hydrothermal brines at Shang Gongtang might have leached metals from footwall Neoproterozoic sequences and became, after mixing with normal seawater, an additional source of Ag, Cr, Cu, Pb, Sb, Zn, Ni, PGE, V and other metals.     

贵州织金下寒武统黑色页岩矿物岩石成分及资源利用特征

通过野外采样、化学分析、电子探针(EPMA)和X射线衍射(XRD)分析等手段,研究了贵州织金地区黑色页岩矿物成分、化学组分、微量元素、稀土元素特征。研究区矿样化学成分以SiO_2和Al_2O_3为主,且具有高K低Na的特征。电子探针和X射线衍射分析表明,研究区黑色页岩主要矿物组成有石英、粘土矿物、白云石及黄铁矿等。织金黑色页岩中Pb、Ni、U、V、Cr等金属元素存在不同程度的富集,稀土元素总量为153.2×10~(-6)~224.89×10~(-6),属轻稀土元素富集型。同时从多金属层、页岩气、页岩提钾及近底部含磷铀矿资源等方面讨论了织金黑色页岩资源化利用。织金黑色页岩多金属层含有Mo、V、Ni、Ag及U等多金属元素,具综合利用价值;其中有机碳含量达到页岩气开发大于2%的条件,可进一步开展研究;页岩中伊利石含量较多,可提取黑色页岩中的钾制备含钾复合肥;黑色页岩底部与磷矿层接触带产出磷铀矿,主要为胶状磷铀矿,接触带可作为铀矿找矿的标志层。     

Chemical Profiles across a Jurassic Stratiform Manganese Deposit at Katsuyama in the Mino Terrane of Central Japan: Implications for Depositional Environment, Diagenetic Metal Redistribution and Paleoceanography

Abstract. Inorganic chemical compositions are determined for a series of rocks crossing an Early Jurassic stratiform manganese ore deposit in a chert‐dominant sequence at Katsuyama, in the Mino Terrane of central Japan. The lithology in the vicinity of the manganese ore bed is classified into lower bedded chert, black shale, massive chert, manganese ore and upper bedded chert, in ascending order. The rocks surrounding the manganese deposit are anomalously high in certain elements: Pb (max. 29 ppm), Ni (1140) and Co (336) in the lower bedded chert, Mo (438), As (149), Tl (29) and U (12) in the black shales, V (210) and Cr (87) in the massive chert, and MnO and W (24) in the manganese ore. The aluminum‐normalized profiles reveal a distinct zonation of redox‐sensitive elements: Pb‐Zn, Ni‐Co‐Cu(‐Zn) and U‐Cr in the lower bedded chert, Mo‐As‐Tl in the black shale, V(‐Cr) in the massive chert, and Mn‐Fe‐Ba‐W in the manganese ore, in ascending order. The lower and upper bedded cherts and manganese ore generally exhibit flat rare earth element patterns with positive Ce anomalies, whereas the uppermost part of the lower bedded chert, the black shale and massive chert have flat patterns with weak or nonexistent negative Ce anomalies and weak positive Eu anomalies. The strong enrichment in Ni, Co, W, Tl and As detected in the Katsuyama section is not recognized in other sediments, including those of anoxic deposition origin, but is identified in modern ferromanganese nodules, suggesting that metal enrichment in the Katsuyama section is essentially due to the formation of ferromanganese nodules rather than to deposition in an anoxic environment. The observed elemental zonation is well explained by equilibrium calculations, reflecting early diagenetic formation and associated gradual reduction with depth. The concentration profiles in combination with litho‐ and biostratigraphical features suggest that formation of these bedded manganese deposits was triggered by an influx of warm, saline and oxic water into a stagnant deep ocean floor basin in Panthalassa at the end of the middle Early Jurassic. Paleoceanographic environmental controls thus appear to be important factors in the formation and preservation of this type of stratiform manganese deposit.     

华南下寒武统镍钼矿层中铜铅锌矿物的发现及意义

华南扬子地块是我国古热水沉积成矿作用最为发育的地区之一,其热水沉积特性最早引起我国学者的关注。华南下寒武统黑色岩系中赋存多个与热水沉积成矿作用相关的大型、超大型重晶石矿床与N i-Mo-U-V多金属富集层。进一步研究分布在华南扬子地块黑色岩系中的金属、非金属矿床成因及其地球化学特征,对认识华南乃至全球晚震旦—早寒武世生物与环境演化有着十分重要的意义。本文对华南下寒武统镍-钼富集层矿石进行电子探针研究,识别出黄铜矿、黝铜矿等铜的独立矿物;闪锌矿等锌的独立矿物;方铅矿、白铅矿等铅的独立矿物。研究表明,在镍-钼矿石中这些矿物的发现为镍-钼矿层是热水沉积作用产物提供了直接的矿物学证据。     

湘西北地区镍钼多金属矿床的成因归属

湘西北地区下寒武统底部黑色页岩中的镍钼多金属矿床，受区域性断裂严格控制，矿床良海底补给与化学沉积两套成矿系统，有较典型的喷气岩一硅质岩和筒状矿体，以及特殊的Ｎｉ、Ｍｏ、Ｖ、Ｐ，Ｐｄ、Ｐｔ、Ｂａ元素组合和高Ｂａ值，反映出这类矿床的成因属性，并非陆源搬运沉积，而是海底喷气沉积矿床。     

广西金秀寒武系黑色岩系中的热液脉状镍钴矿床超常富集规律与成矿条件

在华南地区的广西金秀寒武系黑色岩系中发现了热液脉状镍钴矿床,矿石品位超常富集,元素组合特殊,实属罕见,具有重要的科学价值和找矿意义。本文介绍龙华矿床的地质特征和矿石富集规律,以及矿物学和地球化学初步研究成果。含矿围岩是寒武系清溪组下段炭质泥岩,矿体可分为高品位热液脉状和低品位浸染状2类。主矿脉中出现镍-钴-砷和镍-钴-硫两类矿物组合,且两者呈分离状态,分别赋存在NWW向和NNW向断裂构造中。矿石成分主要是镍-钴砷化物、少量硫化物,以及石英和碳酸盐。采用电子探针方法分析了红砷镍矿、辉砷镍矿、硫镍矿、针镍矿、方钴矿、辉铋矿和自然铋矿物的元素含量,讨论了主要矿石矿物的Fe-Co-Ni三元图解。根据矿物内部结构构造和共生关系,厘清了矿物生成顺序,将矿石矿物的形成过程划分为内生热液作用期和表生作用期。元素面扫描分析结果表明,红砷镍矿内部Ni、Co、S元素具有显著的分带特征,可能是二次生长的结果。热液脉状镍钴矿床可能是加里东运动以前的古老地壳物质再循环的产物,花岗岩体与成矿作用的关系尚难评判,Ni-Co元素的超常富集可能主要来自于后期的构造-流体改造作用。     

湖南省寒武系黑色岩系页岩型钒矿概论

湖南省寒武系黑色岩系蕴藏着丰富的钒矿资源,钒矿床产于寒武系底部富含有机质的碳、磷、硅质黑色岩系中;矿体呈层状、似层状,形态简单,产状稳定。多项测试结果表明,钒的载体岩石为黑色页岩(碳质页岩、硅质碳质页岩);钒主要呈类质同象形式赋存于伊利石晶格中;矿石类型主要为钒矿石,少数矿床中石煤钒矿石也是重要的矿石类型;钒的价态以V3+为主。钒的富集主要发生在沉积阶段,与黑色岩系的沉积过程一致;矿床形成于缺氧环境中,大部分钒被黏土质吸附,随有机质、黏土质和硅质呈胶态腐泥沉入海底;在成岩过程中,云母类黏土矿物结构发生再结晶,将原有表面吸附的钒(V3+)转化为类质同象形式进入云母晶格中取代部分铝(Al3+),形成含钒伊利石并聚集成为钒矿床。研究表明,本区黑色岩系及其有关的钒矿在沉积成岩成矿过程中都离不开生物地球化学作用,矿床成因属于在热水作用参与下沉积形成的海相化学和生物地球化学沉积矿床,矿床类型为黑色页岩型钒矿。     

Sequence of mineral formation in clastic ores of the Saf’yanovka volcanic-hosted copper massive sulfide deposit,the Central Urals

The bedded clastic ore widespread on the slopes and flanks of the deeply eroded sulfide mound at the Saf’yanovka volcanic-hosted copper massive sulfide deposit consists of products of destruction of the Paleozoic black smoker along with diverse newly formed sulfides. The size of ore clasts gradually decreases with distance from the massive ore mound, from more than tens of centimeters to a few millimeters. The clastic sediments are characterized by good preservation of sulfide material composed of hydrothermal sedimentary colloform pyrite, chalcopyrite with lamellae of relict isocubanite, and concentrically zoned sphalerite. Numerous pyrite framboids, nodules, and euhedral crystals; chalcopyrite segregations; and twinned sphalerite are typical of sulfide-bearing black shale. Enargite, tennantite, and galena were formed after pyrite, filling interstices between nodules or partially replacing and corroding the previously formed minerals. The interrelations between minerals show that the fine-clastic sulfide-bearing black shale underwent diagenesis in the presence of organic matter.     

Fluid Inclusions and C,H, O,S, and Pb Isotopic Compositions of the Dabaoshan Cu Polymetallic Deposit,Northern Guangdong Province,South China

The Dabaoshan deposit in Northern Guangdong Province, South China, is a Cu–Mo–W–Pb–Zn polymetallic deposit, located in the southern part of the Qin–Hang porphyry–skarn Cu–Mo ore belt. The deposit mainly comprises porphyry Mo and stratiform skarn Cu ore deposits. The genesis of the Cu ore deposit has been ascribed to a typical skarn ore deposit formed by the metasomatism of Devonian carbonate rock layers or to a volcanic rock‐hosted massive sulfide deposit formed by marine exhalation. In this paper, we report on the homogenization temperatures and salinities of fluid inclusions and C, H, O, S, and Pb isotopic compositions of fluids and minerals in this deposit. Homogenization temperatures and salinities of fluid inclusions in garnet, diopside, quartz, and calcite provide information on the skarnification, mineralization, and postmineralization stages. The data show that ore‐forming fluids experienced a continuous transition from high temperatures and salinities to low temperatures and salinities over the entire period of mineralization. C, H, and O isotopic compositions indicate that ore‐forming fluids were derived mainly from magmatic water. O isotopic compositions indicate that ore‐forming fluids mingled with atmospheric water during the last stage of mineralization. Sulfur in the ore came mainly from deep magmatic sources. Pb isotopic compositions in the orebody show that almost all the lead in the ore was derived from magma with a crustal source. Combined geological, geophysical, and geochemical data were achieved before we proposed that the Dabaoshan porphyry–skarn Cu–Mo–W–Pb–Zn deposit, as one member of the Qin–Hang porphyry–skarn Cu–Mo ore belt, formed during the Jurassic subduction of the paleo‐Pacific plate beneath the Eurasian continent at quite low angle. NE‐ and EW‐trending structures controlled the emplacement of magmatic rocks in the South China region. In the mining area, the Xiangguanping Fault and its branches were the main conduits for magmatic crystallization and mineralization. The many subfaults, folds, and interlayer fracture zones on both sides of the main fault provided the requisite space for the ore and, together, were the controlling structures of the orebody.     

陕西紫阳下寒武统黑色岩系地球化学特征及成因研究

通过野外研究发现陕西紫阳下寒武统黑色岩系富含多种矿产且成因复杂,主要由硅质岩、灰岩、碳质硅质灰岩、碳硅质页岩四类组成。据此进行了系统的元素地球化学分析,结果显示研究区黑色岩系富含V、Mo、As、Ba等元素,不同岩性稀土模式曲线总体特征相似指示成因联系密切。四类岩性样品各自的MnO/TiO₂均值接近或小于0.5、V/（V+Ni）均值大于0.57、V/Cr均值大于4.2等特征表明该套黑色岩系形成于浅海—半深海相缺氧还原环境。另外,As和Sb的富集、Zn?Co?Ni图解中投点大部分位于热液矿床区域、Sr/Ba小于1、La/Ce均值接近2.8、北美页岩标准化配分图解的Eu负异常—弱正异常均指示了热液参与下的正常海水沉积环境。研究区地层夹含的硅质岩和重晶石等热水沉积岩反映了同沉积时的热液活动。据此推断沉积环境是海水、热液和生物的共同作用下形成的浅海—半深海相缺氧的还原环境。     

湘中南华系大塘坡组锰矿地球化学特征及其意义

湘中湘潭盆地大塘坡组锰矿是湖南重要的锰矿基地。盆地内发育一组NNE向同沉积断裂,形成了一系列凹陷带（断陷槽）,控制了沉积岩相的分布,锰矿主要产于盆地凹陷带的黑色页岩夹碳酸锰矿微相内。矿石中Co、Zn、Pb、Mo和Ba等元素丰度较高,Co/Ni、SiO2/Al2O3、(Fe+Mn)/Ti、Al/(Fe+Mn+Al)比值以及Co/Zn-(Cu+Ni+Co)和Fe-Mn-(Cu+Ni+Co)图解都揭示锰矿成矿过程中有海底热水的参与;稀土元素分布模式、Ce、Eu异常表示锰矿形成于被动大陆边缘环境,并具有热水沉积特征;碳同位素结果显示出富集碳的轻同位素的特征,反映了湘中地区锰矿中碳同位素热水沉积的特征;氧同位素计算古温度为湘中地区锰矿的低温热水沉积成因提供了有利的佐证。     

贵州遵义黄家湾下寒武统牛蹄塘组镍-钼富集层电子探针研究

对贵州遵义黄家湾下寒武统牛蹄塘组镍-钼富集层进行电子探针研究,发现镍主要赋存于黄铁矿、针镍矿、辉砷镍矿、铁辉砷镍矿、紫硫镍矿、赫硫镍矿;钼主要以"碳硫钼矿"的形式存在。镍钼硫化物多与黄铁矿、白铁矿交代共生,反映矿物经历了不同的成矿阶段。岩石中不仅富集Ni、Mo元素,而且Se元素存在超常富集,可以视为热液作用或生物作用的结果。遵义黄家湾下寒武统Ni-Mo富集层应为海底热液沉积和生物沉积混合成因,其物源较为复杂。