凡口铅锌矿床海底热泉喷溢成矿的地质地球化学特征

凡口铅锌矿是发育于海相碳酸盐岩建造中的海底热泉喷溢沉积矿床。在研究矿床地质特征和地球化学特征的基础上,总结了发育于同沉积断裂两侧的矿体的形态、产状,矿石组构,成矿元素、微量元素、稀土元素的组成与分布,成矿温度和流体的性质,提出了热泉成矿作用与海相碳酸盐沉积作用同时演化的结论。     

四川西部现代热泉沉积物地球化学特征及意义

西南三江地区现代热泉很发育,但以往对其成矿作用研究不够。笔者发现在四川西部义敦热坑和理塘热水塘两处热泉群产地普遍存在硅化和黄铁矿化现象。地表热泉沉积物主要是硅华和钙华及其过渡类型,大多数是硅华和钙华的混合堆积物。在地表泉华、断裂裂隙充填物及其蚀变围岩中存在金矿化,金质量分数从＜0.1×10^-6到1.89×10^-6。泉华和蚀变围岩中亲花岗岩元素Li、Be、Mo、Ga、Rb、Cd等含量高于地壳丰度值,可作为找矿指示元素。热泉沉积物的地球化学特点总体上与现代海底热泉沉积物比较接近,但成因不同。鉴于三江地区热泉广布,成矿条件有利,建议加强勘查和研究,以期找矿突破。     

腾冲热海地热田高温热泉中的硫代砷化物及其地球化学成因

以我国大陆范围内典型的岩浆热源型水热系统——云南腾冲热海为研究区,在国内首次对热泉中硫代砷化物含量及其地球化学成因进行了分析.研究采用的在野外对富硫化物水样进行快速冷冻处理、而后在实验室进行砷的形态分离和测试的方法明显优于当前通用的水样砷含量及其形态分析的预处理和测试方法.主要原因为后者在采样现场对水样的酸化处理可使样品中三硫代砷酸盐以非定形态硫砷化合物的形式沉淀,且用常规阴离子交换柱在野外无法实现硫代砷酸盐的完全回收及其与砷酸盐的分离.受岩浆流体输入和热储内高温条件下强烈流体-岩石相互作用的控制,热海水热系统排泄的中性-偏碱性热泉中富集硫化物和砷,为热泉中硫代砷化物的形成提供了必要条件.热海热泉中检出的硫代砷化物包括一硫代砷酸盐、二硫代砷酸盐和三硫代砷酸盐,在总砷中所占比例最高分别可达26.7%、43.3%和33.7%.热海地热田的2个子区(硫磺塘和澡塘河) 的热泉沿不同断裂带出露,地热水升流过程中经历的冷却方式也不同,使硫磺塘热泉具有相对较高的总硫化物含量和总砷含量,并导致其中各类硫代砷酸盐具有更高的含量范围.      

西藏搭格架高温热泉中砷的地球化学异常及其存在形态

西藏搭格架高温热泉是我国大陆少有的大型间歇性喷泉,砷元素作为对人类威胁极大的环境问题普遍存在于热泉之中,搭格架高温热泉中砷元素质量浓度最高已达到了9.75 mg/L,其对地表水和浅层地下水的污染不容忽视。硫代砷是富含硫化物热泉中砷的存在形态之一,鉴于国内相关研究较少,本文对西藏搭格架地热区的热泉样品进行了水化学分析,并利用水文地球化学模拟软件PHREEQC开展了对热泉中砷元素存在形态的地球化学模拟。结果表明：西藏搭格架热泉中砷元素的存在形态有亚砷酸盐、砷酸盐和硫代砷,其中亚砷酸盐与砷酸盐是砷的主要存在形态,且在pH影响下两者之间存在相互转化关系;各种硫代砷按质量浓度由高至低依次为一硫代砷酸盐、三硫代砷酸盐、二硫代砷酸盐、一硫代亚砷酸盐、四硫代砷酸盐;硫代砷形态占总砷浓度比例主要受热泉中硫化物质量浓度、Eh（氧化还原电位）和pH等因素的控制,在硫化物质量浓度总体偏低的情况下,硫化物质量浓度的上升可促进其他形态的砷向硫代砷形态转化,强还原性环境有利于硫代砷形态的存在;此外,在中性环境下,硫代砷占总砷浓度比例随pH上升亦有上升趋势。     

勘察加岛弧岩浆岩研究进展

西太平洋分布了全球大部分的洋内俯冲带,也是全球沟-弧-盆体系最发育的地区。勘察加(Kamchatka)半岛位于俄罗斯远东地区,地处太平洋西北部(51°~60°N、155°~164°E),是全球环太平洋岛弧的重要组成部分。前人对勘察加岛弧岩石地幔源区性质、熔融过程、岩浆结晶分异及熔/流体交代过程进行了详细的研究,并获得了丰硕的成果。最新的研究进展表明:(1)勘察加岛弧前缘火山和中部火山的源区主要为亏损地幔,而弧后区域则存在较为富集的地幔贡献;(2)勘察加岛弧不同区域的地幔源区流体性质具有一定的差异,导致从前缘火山至中部火山,地幔熔融程度逐渐降低;(3)勘察加岛弧不同区域岩石地球化学成分存在差异,而且,沿穿弧剖面某些元素或同位素(如δ11 B)表现出系统变化的特征,反应了俯冲板片流体通量和流体性质的差异;(4)勘察加半岛部分多期次火山(如Klyuchevskoy火山)地球化学成分复杂,可能反应了源区熔融条件的不同和岩浆结晶分异过程;(5)勘察加岛弧北部与阿留申岛弧近直角相交,导致异常的构造背景,促使该区域形成了具有埃达克质特征的岛弧岩浆。     

云南腾冲热泉金的有机地球化学研究——Ⅰ生物标志物浅析

本文主要通过对比分析研究热泉软泥中的金含量与有机质及含硫化合物的相关性。并测定泉水及软泥中含金量和软泥中有机碳含量，以及对抽提物中的饱和烃和芳烃族组分进行色谱—质谱分析，最后得出的结论：有机质的沉积环境为还原—强还原，有机质属于腐泥－腐殖型，接近和达到了成熟阶段。软泥中金含量与有机质的性质无明显相关关系，与有机碳含量也无明显相关关系，而与其成熟度相关密切。样品分析证实软泥中含硫化合物与金含量呈正相关性。对比分析了水及软泥中金含量，认为两者之间也无明显相关关系     

云南腾冲地区地热流体的地球化学特征

对云南热海和瑞滇地区地热流体的地球化学特征进行了分析和探讨,并据此评估了地热流体对环境的影响.结果显示,研究区的碱性热泉中K、Na、F、Cl、SiO_2的含量高,而只存在于热海地区的酸性热泉中SO_4~(2-)、Mn、Fe的含量高.热泉中As、Sb的含量范围分别在43.6～687μg/L和0.38～23.8 μg/L之间.热泉中以As(Ⅲ)为主,占了总砷的91%.地热流体中的As、Sb一部分被固定在泉华中,而另一部分则释放到了环境中,从而进入地下水和下游的田地中,对当地居民的健康造成威胁.     

高温富硫化物热泉中硫代砷化物存在形态的地球化学模拟:以云南腾冲热海水热区为例

天然水环境中地质成因砷的存在是世界范围内对人类威胁极大的环境问题之一.在高温富硫化物地热水中,硫代砷化物是砷的主要存在形态之一.在国内尚无硫代砷化物定量检测方法的背景下,以云南腾冲地热带的热海水热区为典型研究区,基于不同类型硫代砷化物的最新化学热力学数据wateq4f.dat,利用水文地球化学模拟软件PHREEQC开展了不同类型热泉中砷的存在形态的地球化学模拟.结果表明,热海热泉中砷的主要形态是硫代砷酸盐,砷酸盐和亚砷酸盐次之,硫代亚砷酸盐则含量极低;在各类硫代砷酸盐中,按平均百分含量降序依次为:一硫代砷酸盐→三硫代砷酸盐→四硫代砷酸盐→二硫代砷酸盐.pH、Eh和总硫化物含量是热泉中砷的形态分布的控制性因素.在酸性条件下,砷以硫代砷酸盐和亚砷酸盐为主要存在形式;而在中性/偏碱性条件下,砷的形态则以硫代砷酸盐为主,砷酸盐次之.偏还原环境和高硫化物含量是硫代砷化物、特别是三硫代砷酸盐和四硫代砷酸盐稳定存在的有利条件.      

西藏谷露热泉型铯矿床地质地球化学特征与成矿作用

谷露热泉型铯矿床位于西藏那曲县谷露地区,达中型规模。在前期野外地质特征与年代学研究的基础上,对其地质、地球化学特征及成矿作用进行了系统的研究。矿石的构造类型有粗大孔隙状构造,角砾状构造,碎裂叶片状构造,细小孔隙状构造,致密块状构造与鲕状构造。结构类型有粒状结构、胶状结构、生物结构、溶蚀结构、长方体状结构、被膜状结构、球状结构、管状结构等。生物结构在硅华形成的各阶段均普遍存在。硅华的主要矿物为蛋白石,但不同的形成阶段蛋白石的种类不同,第2、第3阶段均为CT蛋白石与石英,而在第4与第5阶段仅出现A-蛋白石, 没有CT蛋白石。蛋白石矿物中的SiO2最高达97.48%,∑（CaO+Na2O + MgO）最高达到3.2%,Cs2O最高可达3.57%。随着由早到晚的变化,SiO2呈现出明显的降低趋势,铯含量则呈升高的趋势。其中第2~4阶段的铯平均含量已经低于铯的工业标准（500×10-6） 。谷露硅华不同阶段的样品在Fe-Mn-Al图解中的位置不同,39件样品中有30件位于生物沉积物区,有9件位于热水沉积物区,硅华的稀土元素含量均比北美页岩的低,Cr、Zr的含量与Th、U的含量均相对一般的热水沉积物低。由早期到晚期,δ30Si呈由高到低、δ18OSMOW由低到高的变化趋势。谷露硅华δ13CPDB与87Sr/86Sr均体现出生物作用的特点,是在深源（至少是下地壳）地质作用下以生物作用为主、热水作用为辅形成的。     

郯庐断裂带温泉气体地球化学

断裂构造带温气体成分及同位素组成特征直接指示断裂带的构造活动及水化学特征。郯庐断裂带温泉气体成分以N2为主（多数大于90％）,CO2含量较低（多数小于1％）。δCco2在南北不同地段存在明显差异,北段为－5．8‰－－7．8‰,CO2主要为岩石化学成因。而中段和南段δ^13Cco2均小于－10‰,CO2有机成因。^40Ar/^36Ar为295－363,其中较低者（300左右）主要来源于大气,较高者来自地壳岩石中^40K的衰变。本文研究成果不仅有助于探讨断裂带不同地段温泉气体的组成及其来源,而且有助于揭示郯庐断裂带构造－岩浆活动及水文地球化学特征。     

Stable Isotope and Element Geochemistry of Saline Springs in Evaporite-bearing Mengla Basin,South Yunnan,China

正1 Introduction Mengla Basin is a sub-basin in southern evaporitebearing Lanping-Simao Basin.There are many salt springs in the basin.In 2012,11 spring samples were collected for analyses of chemistry and boron,hydrogen and oxygen     

Microbial Mediated Mineralizationin Kamchatka Hot Springs

正Materials deposited in low-temperature environments are characterized by their small particle size.The activity of microorganisms in aqueous sedimentary environments may have effective impacts on the geochemical     

Controls on the genesis of a high-fluoride thermal spring: Innot Hot Springs,north Queensland *

This study reports on the source, evolution, reactions and environmental impacts of F-rich thermal water at Innot Hot Springs, north Queensland. Thermal water of the Innot Hot Springs has a surface temperature of 71°C, alkaline pH (8.1), low dissolved oxygen (0.61 mg/L) and low total dissolved solids (652 mg/L). The main chemical composition is Na – Cl, with F concentrations (16 mg/L) being comparatively high. Concentrations of alkali and alkali-earth metals (Cs, Li, Rb, Sr) are elevated, while those of other trace elements (Ag, Al, As, Ba, Be, Cr, Cu, Ga, Mn, Mo, U, Zn) are significantly less. Hydrochemical and stable isotope data of hot spring water show that the fluid is meteoric in origin and has undergone significant water – granite interaction. Common geothermometers suggest temperatures of water – rock interaction at depth in the 119 – 158°C range (corresponding to a depth of <3.9 – 5.2 km). Solubility modelling of the thermal fluid demonstrates that the evolution of F concentrations in spring waters at the discharge site can be accounted for by fluid – rock interaction of a H₂O – NaCl solution with fluorite – calcite-bearing granite assemblages between 150 and 200°C and subsequent granite-buffered cooling. Modelling also indicates that the F concentration in the hydrothermal system is largely controlled by interactions with fluorite, with less evidence for the significant involvement of F-topaz. Speciation calculations demonstrate that F speciation in the fluid is dominated by F^? (99.4%), followed by minor CaF⁺ (0.5%) and NaF_(aq) (0.1%), and traces of other F complexes. Thus, the F-rich Innot Hot Springs result from meteoric water circulating through fluorite-bearing granitic rocks and are the surface expression of a low-temperature, non-volcanic geothermal system. Discharge of the hot spring water occurs into an ephemeral stream located in a seasonally wet – dry tropical climate. As a result, the F content of local surface waters is distinctly elevated (max. 18 mg/L) during the dry season, making them unsuitable for stock water supplies.     

Reconnaissance paleomagnetism of Late Triassic blocks, Kuyul region, Northern Kamchatka Peninsula, Russia

The northernmost Kamchatka Peninsula is located along the northwestern margin of the Bering Sea and consists of complexly deformed accreted terranes. Progressing inland from the northwestern Bering Sea, the Olyutorskiy, Ukelayat and Koryak superterranes (OLY, UKL and KOR) are crossed. These terranes were accreted to the backstop Okhotsk-Chukotsk volcanic-plutonic belt (OChVB) in northernmost Kamchatka. A sedimentary sequence of Albian to Maastrichtian age overlaps the terranes and units of the Koryak superterrane, and constrains their accretion time. A paleomagnetic study of blocks within the Kuyul (KUY) terrane of the Koryak superterrane was completed at two localities (Camp 2: λ=61.83°N, φ=165.83°E and Camp 3: λ=61.67°N, φ=164.75°E). At both localities, paleomagnetic samples were collected from Late Triassic (225–208 Ma) limestone blocks (2–10 m in outcrop height) within a melange zone. Although weak in remanent magnetization, two components of remanent magnetization were observed during stepwise thermal demagnetization at 32 sites. The A component of magnetization was observed between room temperature and approximately 250 °C. This magnetic component is always of downward directed inclination and shows the best grouping at relatively low degrees of unfolding. Using McFadden–Reid inclination-only statistics and averaging all site means, the resulting A component mean is I_opt=60.3°, I₉₅=5.0° and n=36 (sites). The B magnetic component is observed up to 565 °C, at which temperature, most samples have no measurable remanent magnetization, or growth of magnetic minerals has disrupted the thermal demagnetization process. Combining sites with Fisher estimates of kappa (k-value)≥13 and n (sites)≥3, where bedding orientation differs within a block, most of these sites show the best grouping of B component directions at 100% unfolding, and two of the blocks display remanent magnetizations of both upward and downward directed magnetic inclination. Combining sites with Fisher estimates of kappa (k-value)≥13 and n (sites)≥3, the resulting overall B component paleolatitude and associated uncertainty are λ_obs=30.4°N or S, λ₉₅=8.9° and n=19 (sites). When compared with the expected North America paleolatitude of λ_{APWP expected}=57.9°N, our data support a model in which blocks within the Koryak superterrane are allochthonous and far travelled.     

Geochemical characterization of marker tephra layers from major Holocene eruptions,Kamchatka Peninsula,Russia

Kamchatka Peninsula is one of the most active volcanic regions in the world. Many Holocene explosive eruptions have resulted in widespread dispersal of tephra-fall deposits. The largest layers have been mapped and dated by the ¹⁴C method. The tephra provide valuable stratigraphic markers that constrain the age of many geological events (e.g. volcanic eruptions, palaeotsunamis, faulting, and so on). This is the first systematic attempt to use electron microprobe (EMP) analyses of glass to characterize individual tephra deposits in Kamchatka. Eighty-nine glass samples erupted from 11 volcanoes, representing 27 well-identified Holocene key-marker tephra layers, were analysed. The glass is rhyolitic in 21 tephra, dacitic in two, and multimodal in three. Two tephra are mixed with glass compositions ranging from andesite/dacite to rhyolite. Tephra from the 11 eruptive centres are distinguished by their glass K₂O, CaO, and FeO contents. In some cases, individual tephra from volcanoes with multiple eruptions cannot be differentiated. Trace element compositions of 64 representative bulk tephra samples erupted from 10 volcanoes were analysed by instrumental neutron activation analysis (INAA) as a pilot study to further refine the geochemical characteristics; tephra from these volcanoes can be characterized using Cr and Th contents and La/Yb ratios.

Unidentified tephra collected at the islands of Karaginsky (3), Bering (11), and Attu (5) as well as Uka Bay (1) were correlated to known eruptions. Glass compositions and trace element data from bulk tephra samples show that the Karaginsky Island and Uka Bay tephra were all erupted from the Shiveluch volcano. The 11 Bering Island tephra are correlated to Kamchatka eruptions. Five tephra from Attu Island in the Aleutians are tentatively correlated with eruptions from the Avachinsky and Shiveluch volcanoes.     

俄罗斯堪察加中部Baranevskoy金-银矿床矿物学与流体包裹体研究

Baranevskoy金-银矿床产于巴尔喀什火山的火山口,该火山坐落在堪察加中部矿区东南部。本文基于矿物学原理和流体包裹体数据分析探讨了Baranevskoy金-银矿床的成矿环境及其物理化学条件。Baranevskoy金-银矿床的围岩为中新世—上新世的安山岩和玄武岩。热液蚀变活动随深度逐渐变化,从而可以进一步划分出最深部的石英带、中部的石英-绢云母(明矾石)-黄铁矿-铁钛氧化物带及其伴生的石英-绢云母-伊利石-黄铁矿矿物组合和浅部的石英-冰长石-水云母-黏土矿物-碳酸盐岩带。成矿早期存在密集浸染的铜矿化,主要矿石矿物有黄铜矿、斑铜矿、砷黝铜矿-黝铜矿,并在Rhzavaya矿脉中存在少量的自然金。其中砷黝铜矿-黝铜矿系列以砷黝铜矿和黝铜矿两个端员作为代表,且以黝铜矿为主。成矿后期产出代表晚期金-银矿化的自然金、黄铁矿、黄铜矿、闪锌矿、方铅矿、碲化物和硫酸盐等标志性矿物。早期铜矿化(第一期)被认为是中硫阶段,紧随其后的为低硫型金-银矿化(第二期和第三期)。金从第一期到第三期都有沉淀。经研究发现,自然金也赋存于变质围岩的岩石裂隙内。早期的自然金相对富银,其中金的摩尔分数为59%~65%,低于后期(第二、第三期)自然金中金的摩尔分数(64%~72%)。流体包裹体显微测温结果显示,位于中部(Central)矿脉的包裹体均一温度为190~280 ℃,Rzhavaya矿脉的包裹体为190~240 ℃,产出自然金的蚀变围岩中石英的包裹体温度为230~310 ℃。包裹体总体表现出低盐度(0.9%~2.4% NaCl_eq)特征,推测存在大气水的混入。     

Origin and evolution of the Steamboat Springs siliceous sinter deposit, Nevada, U.S.A.

Siliceous hot spring deposits from Steamboat Springs, Nevada, U.S.A., record a complex interplay of multiple, changing, primary environmental conditions, fluid overprinting and diagenesis. Consequently these deposits reflect dynamic geologic and geothermal processes. Two surface sinters were examined—the high terrace, and the distal apron-slope, as well as 13.11 m (43 ft) of core material from drill hole SNLG 87-29. The high terrace sinter consists of vitreous and massive-mottled silica horizons, while the distal deposit and core comprise dominantly porous, indurated fragmental sinters. Collectively, the three sinter deposits archive a complete sequence of silica phase diagenetic minerals from opal-A to quartz. X-ray powder diffraction analyses and infrared spectroscopy of the sinters indicate that the distal apron-slope consists of opal-A and opal-A/CT mineralogy; the core yielded opal-A/CT and opal-CT with minor opal-A; and the high terrace constitutes opal-C, moganite, and quartz. Mineralogical maturation of the deposit produced alternating nano–micro–nano-sized silica particle changes. Based on filament diameters of microbial fossils preserved within the sinter, discharging thermal outflows fluctuated between low-temperatures (< 35 °C, coarse filaments) and mid-temperatures ( 35–60 °C, fine filaments). Despite transformation to quartz, primary coarse and fine filaments were preserved in the high terrace sinter. AMS ¹⁴C dating of pollen from three horizons within core SNLG 87-29, from depths of 8.13 to 8.21 m (26′8″ to 26′11″), 10.13 to 10.21 m (33′3″ to 33′6″), and 14.81 to 14.88 m (48′7″ to 48′10″), yielded dates of 8684 ± 64 years, 11,493 ± 70 years and 6283 ±60 years, respectively. In the upper section of the core, the stratigraphically out-of-sequence age likely reflects physical mixing of younger sinter with quartzose sinter fragments derived from the high terrace. Within single horizons, mineralogical and morphological components of the sinter matrix were spatially patchy. Overall, the deposit was modified by sub-surface flow of alkali-chloride thermal fluids depositing a second generation of silica, and periodically, by acidic steam condensate formed during periods when the water table was low. Local faulting produced considerable fracturing of the sinter. Hence, the Steamboat Springs sinter experienced a complex history of primary and secondary hydrothermal, geologic and diagenetic events, and their inter-relationships and effects are locked within the physical, chemical and biological signatures of the deposit.     

搭格架温泉水化学特征及其约束因素研究

搭格架地热区温泉水DJ1-DJ116号样品于2009年采集,阳离子及微量元素含量采用ICP-OES法测试,Cl-含量采用滴定法测试,其余阴离子含量采用紫外-可见光分光光度法测试。通过对温泉水化学指标的分析,研究温泉的水化学特征及约束因素。其温泉水化学类型为HCO3-Na型,平均矿化度为1 524 mg/L,具有较高的Na/Cl值,温泉水演化程度较高,为完全平衡水,热储中的水岩反应达到了平衡状态.温泉水中PO2极低,PCO2较高;大部分温泉水中玉髓、石英和无定形态SiO2三种硅质热液矿物的饱和度指数大于0。K-Na温标计算热储平均平衡温度为251.36℃;泉水中的Na＋、K＋离子活度主要受到钠、钾长石的约束。微量元素组合表现出花岗岩源的特征。总体上搭格架地热区温泉水化学特征受到区域地质背景的约束。     

Ore‐forming Ages and Sulfur Isotope Study of Hydrothermal Deposits in Kamchatka,Russia

In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ³⁴S_CDT of sulfides are ?2.8‰ for the Ametistovoe deposit in Central Koryak, ?1.8‰ to +2.0‰ (av. ?0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and ?0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ³⁴S_CDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of ³²S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition.