Multiple Foliations Defined by Different Sillimanite Crystal Habits, Partial Melting and the Late Metamorphic Development of the Cannington Ag-Pb-Zn Deposit, Northeast Australia

A succession of foliations defined by different sillimanite-bearing structural fabrics suggests that the macroscopic, isoclinal synform that dominates the geometry of the Cannington Ag-Pb-Zn deposit, northwest Queensland, Australia formed during D₂. The five foliations in this succession, S₁ to S₅, are defined by aligned sillimanite with habits ranging from individual crystals in S₁ through S₄ to clusters of fibrolite in S₅ in both the matrix and as inclusion trails within garnet and gahnite (Zn-rich spinel) porphyroblasts. S₁, S₃ and S₅ formed as sub-horizontal foliations, whereas S_1a, S₂ and S₄ formed sub-vertically. Foliation intersection/inflexion axes (FIAs) within garnet and gahnite porphyroblasts preserve a succession of trends that shifts from W-E to N-S. This succession indicates that this region experienced N-S followed by W-E bulk crustal shortening. N-S shortening occurred during D₁and D_1a, and W-E shortening occurred from D₂ to D₅. Prismatic and rhombic sillimanite produced during D₁-D₄ accompanied prograde metamorphism to ca. 634 62°C and 4.8 1.3 kbar. The coexistence of fibrous, prismatic and rhombic sillimanite resulted from post peak metamorphic reactivation of the early foliations during D₅. The synformal D₂ fold was intensified during D₄ by W-E bulk shortening. Local partial melting occurred after D₁ in the appropriate bulk rock compositions, based on calculation of P-T pseudosections in the chemical systems KFMASH, KFMASHTO, NCKFMASH and MnNCKFMASH. Zn mineralization related to gahnite growth occurred during D₃ through D₄, and was redistributed by partial melting into structural and rheological sites during D₄ and D₅shearing.     

Development of Cu and Zn Isotope MC-ICP-MS Measurements: Application to Suspended Particulate Matter and Sediments from the Scheldt Estuary

The present study evaluates several critical issues related to precision and accuracy of Cu and Zn isotopic measurements with application to estuarine particulate materials. Calibration of reference materials (such as the IRMM 3702 Zn) against the JMC Zn and NIST Cu reference materials were performed in wet and/or dry plasma modes (Aridus I and DSN‐100) on a Nu Plasma MC‐ICP‐MS. Different mass bias correction methods were compared. More than 100 analyses of certified reference materials suggested that the sample‐calibrator bracketing correction and the empirical external normalisation methods provide the most reliable corrections, with long term external precisions of 0.06 and 0.07‰ (2SD), respectively. Investigation of the effect of variable analyte to spike concentration ratios on Zn and Cu isotopic determinations indicated that the accuracy of Cu measurements in dry plasma is very sensitive to the relative Cu and Zn concentrations, with deviations of δ⁶⁵Cu from ?0.4‰ (Cu/Zn = 4) to +0.4‰ (Cu/Zn = 0.2). A quantitative assessment (with instrumental mass bias corrections) of spectral and non‐spectral interferences (Ti, Cr, Co, Fe, Ca, Mg, Na) was performed. Titanium and Cr were the most severe interfering constituents, contributing to inaccuracies of ?5.1‰ and +0.60‰ on δ^68/64Zn, respectively (for 500 μg l^?1 Cu and Zn standard solutions spiked with 1000 μg l^?1 of Ti or Cr). Preliminary isotopic results were obtained on contrasting sediment matrices from the Scheldt estuary. Significant isotopic fractionation of zinc (from 0.21‰ to 1.13‰ for δ⁶⁶Zn) and copper (from ?0.38‰ to 0.23‰ for δ⁶⁵Cu), suggest a control by physical mixing of continental and marine water masses, characterized by distinct Cu and Zn isotopic signatures. These results provide a stepping‐stone to further evaluate the use of Cu and Zn isotopes as biogeochemical tracers in estuarine environments.     

豫西熊耳山地区重磁场特征与深部成矿预测

熊耳山地区是河南省重要的金银铅锌钼多金属矿产地,现已查明各类矿床(点)121个。通过研究发现,该区多金属矿产的形成与中生代中酸性岩浆的侵入活动关系密切,现有矿床分布比较集中的区域,深部都有隐伏岩体赋存。通过对熊耳山地区重磁场特征的分析,建立了熊耳山地区隐伏岩体侵入模型。熊耳山西段主要是寨凹隐伏岩体,赋存面积约310 km2,分3个阶梯深度:0~0.8 km、0.8~2 km、2~4 km;熊耳山中段铁炉坪-花山隐伏岩体位于寨凹隐伏岩体和花山岩体之间,赋存面积约184 km2,深度3~5 km;熊耳山东段旧县-花山隐伏岩体,赋存面积约338 km2,北部深度0~1.5km,向南逐步加深至1.5~3 km。根据区域矿产分布分带特征,结合隐伏岩体侵入模型,预测了深部成矿模型。研究表明,在熊耳山西段有寻找大型斑岩型钼钨铜矿和大型金矿的潜力;中段隐伏岩体深度较大,以寻找中低温矿产为主;东段地质勘查程度相对较高,深部仍有寻找斑岩型钼金铜矿的潜力。     

Stable isotope study of the mineralization and alteration in the Madjarovo Pb–Zn district,south-east Bulgaria

The Madjarovo ore district is centred on the exposed section of a Lower Oligocene volcano and consists of radially disposed Pb–Zn-precious metal veins and attendant intermediate sulfidation wallrock alteration. Earlier high sulfidation and potassic porphyry style alterations are found in the centre of the district spatially associated with monzonitic intrusions. The total duration of all mineralization and alteration was ca. 300 ka. Stable isotope analyses (S, O, H) have been carried out on a suite of sulfides, sulfates and silicates from the mineralization, high and intermediate sulfidation alterations and a suite of basement rocks. These data range between the following limits: . We also analysed δD of fluid inclusions in quartz and barite for which we obtained, respectively, the ranges of −43.6 to −78.6 and −58.4 to −67.1‰. The data show that high sulfidation alteration was dominated by magmatic fluids with minor meteoric water, whereas the fluids responsible for the intermediate sulfidation alteration were essentially magmatic. The fluids responsible for the intermediate sulfidation Pb–Zn mineralization were mixed magmatic–meteoric and certainly contained a significant meteoric component. Sulphur is likely derived from basement and/or igneous sources. The evolution of alteration and mineralization styles from potassic, porphyry copper style to high sulfidation to intermediate sulfidation can be understood in terms of changing ore fluid composition resulting from an increasing permeability of the system and an increasingly remote source of magmatic fluid with time. These changes link directly to the geological evolution of this volcanic centre.     

Two pulses of mineralization and genesis of the Zhaxikang Sb–Pb–Zn–Ag deposit in southern Tibet: Constraints from Fe–Zn isotopes

Zhaxikang is one large Sb–Pb–Zn–Ag deposit located in the North Himalaya of southern Tibet. To date, the genesis of this deposit still remains controversial. Here, we present new pyrite Fe and sphalerite Zn isotopic data for the first three stages of mineralization, Fe–Zn isotopic data for Mn–Fe carbonate that formed during the first two stages of mineralization, and Zn isotopic data for the slate wall rocks of the Jurassic Ridang Formation to discuss the genesis of the Zhaxikang deposit. The overall δ⁵⁶Fe and δ⁶⁶Zn values range from −0.80‰ to 0.43‰ and from −0.03‰ to 0.38‰, respectively. The δ⁵⁶Fe values of Mn–Fe carbonates are lighter than those of associated pyrite in six mineral pairs, indicating that the iron carbonates are preferentially enriched in light Fe isotopes relative to pyrite. The sphalerite has lighter δ⁶⁶Zn values than associated Mn–Fe carbonates in three mineral pairs.The δ⁵⁶Fe values of pyrite that formed during the first three stages of mineralization gradually increase from stage 1 (−0.33‰ to −0.09‰) through stage 2 (−0.30‰ to 0.19‰) to stage 3 (0.16‰–0.43‰). In comparison, the sphalerite that formed during these stages has δ⁶⁶Zn values that gradually decrease from stage 1 (0.16‰–0.35‰) through stage 2 (0.09‰–0.23‰) to stage 3 (−0.03‰ to 0.22‰). These data, in conjunction with the observations of hand specimens and thin sections, suggest that the deposit was overprinted by a second pulse of mineralization. This overprint would account for these Fe–Zn isotopic variations as well as the kinetic Rayleigh fractionation that occurred during mineralization. The temporally increasing δ⁵⁶Fe and decreasing δ⁶⁶Zn values recorded in the deposit are also coincident with an increase in alteration, again supporting the existence of two pulses of mineralization. The δ⁵⁶Fe values of the first pulse of ore-forming fluid were calculated using theoretical equations, yielding values of −0.54‰ to −0.34‰ that overlap with those of submarine hydrothermal solutions (−1‰ to 0‰). However, the δ⁵⁶Fe values of the stage 3 pyrite are heavier than those of typical submarine hydrothermal solutions, which suggests that the second pulse of mineralization was probably derived from a magmatic hydrothermal fluid. In addition, the second pulse of ore-forming fluid has brought some Fe and taken away parts of Zn, which results the lighter δ⁶⁶Zn values of sphalerite and heavier δ⁵⁶Fe values of pyrite from the second pulse of mineralization. Overall, the Zhaxikang deposit records two pulses of mineralization, and the overprint by the second pulse of mineralization causes the lighter δ⁶⁶Zn values and heavier δ⁵⁶Fe values of modified samples.     

SHRIMP U–Pb ages of zircons from the Lengshuikeng ore field,North Wuyi Mountains,South China: Implications for dating volcaniclastic rocks

The Lengshuikeng Ag‐Pb‐Zn ore field is located in the North Wuyi Mesozoic volcanic belt south of the Qinzhou–Hangzhou suture zone between the Yangtze and Cathaysia paleo‐plates. Previous zircon U–Pb geochronological studies on ignimbrites and tuffs from this area have yielded conflicting ages of 157–161 Ma (Early Upper Jurassic) and 137–144 Ma (Early Lower Cretaceous). Volcanic rocks in the ore field have even been proposed to include both ages. Our SHRIMP zircon U–Pb dating of the ignimbrite and tuff samples from the ore field, along with field observations and results from geochronological work on other volcanic and sub‐volcanic rocks in the region, shows that two populations of magmatic zircons, one autocrystic and the other xenocrystic, are present in the pyroclastic rocks. The autocrystic zircons have ages suggesting formation/eruption at approximately 140 Ma, whereas the xenocrystic zircons give ages of 155–159 Ma, indicating intrusion of granitic porphyries in the Early Upper Jurassic. Therefore, the pyroclastic rocks in the Lengshuikeng Ag–Pb–Zn ore field formed in the Early Lower Cretaceous. The youngest zircon U–Pb ages from pyroclastic rocks may not represent the formation/eruption ages of the host rock, depending most likely on the existence and/or abundance of juvenile or vitric pyroclasts in the rocks.     

铜和锌对刺参幼参的联合毒性作用

采用等毒性配比法,研究了金属离子 Cu2+ 和 Zn2+ 对刺参幼参的联合毒性,并以 Marking 相加指数 ( AI ) 评价联合毒性效应.实验结果表明,当 Cu2+ 和 Zn2+ 以等毒性混合共存时,Cu2+ 对刺参幼参在24 h、48 h、72 h和96 h 的半致死质量浓度 ( LC50 ) 分别为0.351 7、0.283 3、0.249 5和0.234 8 mg/L;Zn2+ 对刺参幼参在24 h、48 h、72 h和96 h的 LC50 分别为 5.061 0、3.223 4、2.469 6和2.163 5 mg/L.由此可见,Cu2+ 对幼参的毒性大于 Zn2+.二者以等毒性混合对刺参幼参在 24 h、48 h、72 h和96 h的相加指数 AI值分别为 -0.931 5、-1.499 0、-1.834 2和-2.065 2,其对幼参24 h、48 h、72 h和96 h的联合毒性均为拮抗作用;并且随着暴露时间的延长,拮抗作用增强.     

重金属毒性对刺参幼参SOD活性的影晌

采用体外慢性毒性实验,研究了3种重金属离子Cd2+、Hg2+和Zn<2+对刺参(Apostichopus japonicus)幼参内脏超氧化物歧化酶(SOD)活性的影响.结果表明,随着3种重金属离子暴露时间的延长,幼参SOD活性发生了明显的变化.0.009～0.046 mg/L的Hg2+对SOD活性的影响在24 h和48 h时表现为诱导效应,96 h的SOD值达到最大,144 h的SOD值下降.0.195～0.976 mg/L的Zn2+对幼参SOD活性的影响48 h表现为诱导效应,96 h和144 h的SOD活性下降.Hg2+和Zn2对幼参SOD活性的影响,均表现为随暴露时间延长,先诱导后抑制的趋势.0.214～1.069 mg/L的Cd2+对幼参SOD活性的影响48 h表现为抑制效应,96 h和144 h表现为诱导效应.     

胶州湾水生系统中Pb、Zn 的分布特征及其在生物体中的浓缩

利用在胶州湾采集的47组同站位多介质样品,进行了痕量金属Pb、Zn及其它环境因子的化学成分测试,讨论了胶州湾水-沉积物-生物系统中Pb、Zn的生物地球化学总体特征及其在各介质平面上的分布,揭示了胶州湾水-沉积物-生物系统对陆源物质输入的响应.垂向上表层沉积物是Pb、Zn组分的富集带,该系统中的生物相对于其所处水环境具有显著的富集作用,生物体中Pb、Zn生物浓缩系数分别为36、935;横向上,Pb、Zn在底层水和沉积物介质中的分布主要受控于河口,即高值区分布于胶州湾的各个主要河口区,特别是在沉积物中金属组分浓度的高值区主要集中分布于胶州湾的东部.而孔隙水中Pb、Zn的高值主要分布于水交替较弱的海域,如红岛前缘.但生物体中的痕量金属组分化学场空间分布规律与上述各介质的化学场均不吻合,亦即是生物体中痕量金属组分的浓度与其所处环境中的同名金属组分浓度无关.作者认为,生物对痕量金属组分的富集并不简单地取决于它所处环境介质中同名金属组分的总量,而存在形态上的选择性.通过回归分析揭示了孔隙水对生物体中Pb、Zn的富集贡献较大.