LA-ICP-MS heavy metal analyses of fish scales from sediments of the Oxbow Lake Certak of the Morava River (Czech Republic)

Heavy metal concentrations were studied in the scales of recent and subrecent (2–25 years old) fish buried in the oxbow lake sediments of the Morava River. The samples were taken from two cores up to 4-m deep and analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and an electron microprobe analysis (EMPA). The results were compared with heavy metal concentrations of bulk samples of the embedding sediment. The study has revealed substantial differences in heavy metal contents existing between the recent and subrecent fish scales documenting an extreme rapidity of the diagenesis/fossilization processes. The most apparent features of the early fossilization include the quick loss of the mucous envelope, collagen and magnesium and an enormous increase in the heavy metal concentrations in particular iron, which is connected with a colour change. The variations in heavy metal contents in fish scales within a sample are attributed to variations in heavy metal content in the environment and variable amounts of organic matter in the embedding sediment. In contrast to the contamination of the embedding sediment, no general increase in heavy metal concentrations in fish scales was observed down to the cores. It is inferred that the rapid sorption stabilizes the biologic hydroxyapatite of the fish scales, which thus rapidly attain a thermodynamic equilibrium with the embedding water-saturated sediment. The results show that the processes of sorption, fossilization and stabilization of hydroxyapatite can act very quickly over a time scale of several years and represent thus a great advantage in the preservation of the original signals of the ancient environments.     

Geochemical modeling of magma mixing and magma reservoir volumes during early episodes of Kīlauea Volcano’s Pu‘u ‘Ō‘ō eruption

Geochemical modeling of magma mixing allows for evaluation of volumes of magma storage reservoirs and magma plumbing configurations. A new analytical expression is derived for a simple two-component box-mixing model describing the proportions of mixing components in erupted lavas as a function of time. Four versions of this model are applied to a mixing trend spanning episodes 3–31 of Kilauea Volcano’s Puu Oo eruption, each testing different constraints on magma reservoir input and output fluxes. Unknown parameters (e.g., magma reservoir influx rate, initial reservoir volume) are optimized for each model using a non-linear least squares technique to fit model trends to geochemical time-series data. The modeled mixing trend closely reproduces the observed compositional trend. The two models that match measured lava effusion rates have constant magma input and output fluxes and suggest a large pre-mixing magma reservoir (46±2 and 49±1 million m³), with little or no volume change over time. This volume is much larger than a previous estimate for the shallow, dike-shaped magma reservoir under the Puu Oo vent, which grew from ∼3 to ∼10–12 million m³. These volumetric differences are interpreted as indicating that mixing occurred first in a larger, deeper reservoir before the magma was injected into the overlying smaller reservoir. Electronic Supplementary Material Supplementary material is available at and is accessible for authorized users.     

Results from a Multi-disciplinary Sedimentary Pilot Study of Tectonic Lake Iznik (NW Turkey) – Geochemistry and Paleolimnology of the Recent Past

A limnogeological reconnaissance study was carried out on Lake Iznik, located in the southeast of the Marmara region of Turkey, involving a seismic survey and collection of short sediment cores. This lake is located on the middle branch of the North Anatolian Fault Zone (NAFZ), a transform plate boundary between the Eurasian and Anatolian Plates. It is, therefore, tectonically active and offers an opportunity to investigate the interplay of sedimentary and seismo-tectonic processes, as well as climate change and human impact in the region. Short cores of the three sub-basins, maximum length of 35.5 cm, recovered non-laminated, blackish clays and silts with varying amounts of biogenic and minerogenic (allochthonous, autochthonous) material, which documented almost the last 80 years of deposition and environmental history. High sedimentation rates in the deeper core sections are accompanied by changes in land use (conversion of woodland to farmland) in the northern areas of Lake Iznik, which caused the deposition of more weathered material (high K/Na ratios) and higher contents of Mn in the lake. A tendency towards eutrophic conditions within the last 20 years is indicated by high nutrient content (N, TOC, P), decreasing C/N-ratios, and characteristic diatom and cladoceran associations. Also increased pollution is revealed by higher Pb, Cu, and Zn contents and increased supply of human and animal faeces (high coprostanol content) during the last two decades. But simultaneous lower sedimentation rates towards the core tops complicate the reconstruction of recent and past eutrophication and pollution states of Lake Iznik. This requires an extension of the pilot study and deeper sediment cores, to recover non-anthropogenic influenced sediment levels.     

Hydrothermal alteration processes in the giant Dahutang tungsten deposit,South China: Implications from litho-geochemistry and mass balance calculation

The giant Dahutang tungsten (W) deposit has a total reserve of more than 1.31 Mt WO₃. Veinlet-disseminated scheelite and vein type wolframite mineralization are developed in this deposit, which are related to Late Mesozoic biotite granite. Four major types of alterations, which include albitization, potassic-alteration, and greisenization, and overprinted silicification developed in contact zone. The mass balance calculate of the four alteration types were used to further understanding of the mineralization process. The fresh porphyritic biotite granite has high Nb, Ta, and W, but low Ca and Sr while the Jiuling granodiorite has high Ca and Sr, but low Nb, Ta, and W concentrations. The altered porphyritic biotite granite indicated that the Nb, Ta, and W were leached out from the fresh porphyritic biotite granite, especially by sodic alteration. The low Ca and Sr contents of the altered Neoproterozoic Jiuling granodiorite indicate that Ca and Sr had been leached out from the fresh granodiorite by the fluid from Mesozoic porphyritic biotite granites. The metal W of the Dahutang deposit was mainly derived from the fluid exsolution from the melt and alteration of W-bearing granites. This study of alteration presents a new hydrothermal circulation model to understand tungsten mineralization in the Dahutang deposit.     

Petrology and structure of the Palaeoproterozoic (1.9 Ga) Rytky nickel sulphide deposit,Central Finland: a comparison with the Kotalahti nickel deposit

The Palaeoproterozoic (1.9 Ga) Rytky and Kotalahti mafic-ultramafic intrusions are located in the contact zone between the Archaean craton and Proterozoic supracrustal rocks. During the second deformation event (D₂) the surrounding country rocks were subjected to intensive metamorphism and deformation associated with the Svecofennian orogeny; the Archaean/Proterozoic boundary controlled both D₂ thrusting and magma ascent. Emplacement of the Rytky and Kotalahti intrusions took place at the culmination of D₂, as shown by the gneiss inclusions with S₂ schistosity within the intrusions. Overthrusting continued after emplacement, with detached fragments of the bodies incorporated into the Archaean gneisses. During the third deformation event (D₃) the originally subhorizontal intrusions were rotated into a subvertical position, so that they now have their stratigraphic top towards the west. The Rytky intrusion is composed mainly of medium- and coarse-grained lherzolite, websterite and gabbronorite. The nickel deposit with pentlandite as the main nickel mineral is associated with the lherzolite and websterite. The coarse-grained lherzolite, websterite and melagabbro represent the first rocks to form, and they contain the nickel sulphide mineralisation. Country rock contamination, as indicated by high TiO₂, P₂O₅, Rb, Zr and light rare earth element contents (LREE), is most pronounced in the marginal part of the intrusion, which was the first to form. The variation in olivine composition (Fo 78.6-84.77 mole %; Ni 630–2386 ppm) and the metal ratio of the sulphide (Ni/Co 19.3 – 50.3) along with the internal stratigraphy of the intrusion indicate an in-situ process of sulphide ore formation.Editorial handling: P. LightfootAn erratum to this article can be found at     

Geochemistry,petrogenesis and tectonic setting of the peraluminous granites in the nacheng gold deposit,Yongning, Guangdong北大核心

The Nacheng granite locates in the Yong ning area, Guangdong Province. This paper studied petrographical and chronological characteristics of this granite as well as its petrogenesis and geological significance. The Nacheng granite mainly consists of quartz (40%-50%), orthoclase (25%-30%), palgioxlase (15%-20%) with minor accessory minerals of quartz apatite and magnetite. Geochemical analyses show that the manziying granite has high content of SiO2 (75. 56%) , K2O (4.72%), Al2O3 (13. 34%) and total alkali (Na2O+K2O=7. 49%), but relatively low MgO (0. 04%-1. 29%) and CaO (0. 39%-2. 21%). The ratios of K2O/Na 2O are generally higher than 1. The Rittmann indexes are between 1-2. 43, belonging to the high-K calc-alkaline series. The values of A/CNK vary from 1. 12 to 1. 32 with an average of 1. 10, showing the characteristics of peraluminous S type granites. Trace element analyses show that the Nacheng granite has relatively high REE content of 82. 6 × 10-6 225. 68 × 10-1, and displays right-inclined V-shape REE patterns with relatively high fractionations of LREE and HREE[(La/Yb)N = 1. 51-9. 66] and pronounced negative Eu anomalies (δEu = 0. 31-0. 74) in the chondrite-normalized REE diagrams, suggesting a typical crust-derived grandite. The magmas may be divided into two types: "low-temperature" type from mudstones and "high-temperature" type from sandstones. The Nacheng granites were formed from the post-orogenic tectonic setting.     

西藏日喀则地区白朗蛇绿岩中石榴辉石岩的岩石地球化学、年代学及其构造意义

白朗石榴辉石岩位于西藏南部雅鲁藏布江蛇绿岩带上,地处于日喀则地区白朗县境内,因其具有重要的大地构造位置和意义,得到了国内外诸多学者关注。国内外学者对该岩体的研究有助于深入剖析雅鲁藏布江蛇绿岩带的就位机制。本文以白朗石榴辉石岩为研究对象,其野外产出为构造岩块,围岩为没有变形特征的蛇纹石化地幔橄榄岩,早白垩世昂仁组和紫红色硅质岩也没有构造变质现象,且石榴辉石岩与蛇纹石化地幔橄榄岩间界限截然。通过对其进行岩石地球化学和年代学的研究,并结合大地构造动力学观点,认为西藏日喀则地区石榴辉石岩属钙碱性超基性岩,形成于无流体无水的稳定物理化学环境中,略亏损高场强元素Th、Ta、Nb等,锆石LA-ICP-MS U-Pb年龄为149.0±3.1Ma,且锆石εHf(t)平均值为+17.7,说明原始岩浆主要源于亏损地幔,且没有发生岩浆混染。总结:本文确定白朗石榴辉石岩原始岩浆来源于上地幔,并且该岩石的形成与印度板块和欧亚板块俯冲有关,但在该岩石形成过程中印度板块和欧亚板块没有发生陆陆碰撞。     

五台杂岩晚太古代花岗质岩石中斜长角闪岩包体的年代学和地球化学研究

华北克拉通中部造山带被认为是由东西部陆块碰撞而产生的陆陆碰撞带,而恒山-五台-阜平地区位于中部造山带的中部,是该地区最大也是最具代表性的基底岩石剖面。总体上,五台杂岩可以分为变质表壳岩和花岗质岩体两大类,前者又被划分为五台群和滹沱群,而后者可划分为2560~2520Ma侵位的强烈变形的闪长岩-英云闪长岩-奥长花岗岩-花岗闪长岩系列、2176~2084Ma侵位的弱变形的斑状正长-钾质花岗岩以及约1810Ma侵位的未变形的A型花岗岩。在晚太古代花岗岩中普遍发育有斜长角闪岩包体,它们在露头上不连续分布,呈绿色到黑色,强烈拉伸成扁条状或透镜状,直径一般在几米到十几米之间。根据地球化学特征恢复它们的原岩为拉斑玄武岩。锆石U-Pb定年结果表明它们的结晶时代为2.7Ga,变质时代为1.85Ga。全岩εNd(t)值为-3.1~+3.5,亏损地幔模式年龄为2.83~3.65Ga。原始地幔均一化蛛网图解上,斜长角闪岩具有明显的Nb、Ta和Ti的负异常,而在球粒陨石均一化稀土元素配分图解中它们具有轻稀土弱富集[(La/Yb)N=1.36~3.52]以及重稀土平坦[(Gd/Yb)N=0.94~1.38]的特征。地球化学以及同位素特征表明它们很可能来自于受到俯冲板片流体改造的轻度富集地幔中尖晶石二辉橄榄岩的部分熔融。更重要地,这些斜长角闪岩包体的锆石U-Pb年龄与全岩Nd亏损地幔模式年龄相似,都为27~28亿年左右,这说明在华北克拉通中部造山带很可能存在过大量的27亿年左右的新生地壳岩石,它们代表了一期重要的地壳生长事件。     

赣南淘锡坑石英脉型钨矿床成矿机制探讨:来自流体包裹体的证据

赣南地区淘锡坑钨矿床是典型的大型石英脉型钨锡多金属矿床。矿体赋存于震旦系浅变质砂(板)岩,并延伸至深部花岗岩内,按空间产出位置分为内带矿体和外带矿体,包括宝山、西山、烂埂子、枫岭坑4大脉组,矿体产出各不相同,矿物组合也具有明显分带特征。在详细的岩相学研究基础上,文章选择淘锡坑主成矿期石英为研究对象,并与共生黑钨矿作对比,从空间角度开展不同脉组、不同矿体或中段的流体包裹体的对比研究。根据流体包裹体岩相学,石英包裹体类型有H_2O-NaCl型包裹体(Ⅰ型)、H_2O-NaCl-CO_2型包裹体(Ⅱ型)和纯CO_2体系裹体(Ⅲ型)及少量含石盐子晶的多相包裹体,并同时捕获贫CO_2的盐水溶液包裹体和纯CO-2气相包裹体。包裹体显微测温结果显示:内、外带石英脉气液两相的包裹体均具有较宽温度和盐度范围,外带均一温度和盐度w(NaCl_(eq))分别集中于200～220℃、1%～6%,内带均一温度和盐度w(NaCleq)分别集中于100～220℃、3%～7%,流体为中-低盐度、富含CO_2的H_2O-CO_2-NaCl体系,不同脉组不同矿脉之间对比结果均显示出多期成矿的特征。在矿脉形成过程中,流体的成分和温度在内外接触带有明显变化,表明岩体与围岩接触界面是造成淘锡坑矿床内带矿体和外带矿体的成矿条件改变的转折位置,成矿流体在此附近发生CO_2逸失引起相分离的不混溶作用是成矿的主要因素。     

阿尔泰额尔齐斯带东段酸性岩墙群地球化学特征及其地质意义

野外地质调查发现在阿尔泰南缘额尔齐斯构造带东段、额尔齐斯活动断裂与富蕴-锡泊渡断裂之间发育了一套未变形的酸性岩墙群.岩墙群侵位于海西期片麻岩化花岗岩和上石炭统深变质的额尔齐斯组岩层中,薄片鉴定和岩石地球化学分析确定为具有细晶结构的流纹斑岩.岩石的SiO2含量为70.9%～75.38%,K2O＋Na2O含量为7.55%～8.99%;大部分样品Na2O＞K2O,里特曼指数值为1.8～2.5之间,Al2O3=12.80%～14.53%,A/CNK=0.9～1.1,NK/A=0.7～0.9,具有准铝质-弱过铝质、低镁、高钾钠、低钙和锶、高（Fe）mol/（Mg）mol特点,具A型花岗岩类特点,属于亚碱性脉岩.岩石轻稀土富集,大离子亲石元素相对富集,具有明显的中等负铕异常,壳源特征明显.锆石U-Pb二次粒子微探针测年显示岩墙群形成于277～286Ma.推断岩墙是阿尔泰海西期造山运动结束后,在拉张构造环境下的地壳局部熔融产物.