中国不同构造单元花岗岩类元素丰度及特征

:依据采自全国范围内750个有代表性的大中型花岗岩类岩体上的767件组合样的实测分析数据,本文计算并提出了天山-兴安造山系、中朝准地台、昆仑-祁连-秦岭造山系、滇藏造山系、扬子准地台、华南-右江造山带、喜马拉雅造山带等中国七大构造单元花岗岩类和不同构造单元碱长花岗岩、正长花岗岩、二长花岗岩中SiO2、Al2O3、Fe2O3、FeO、MgO、CaO、Na2O、K2O、H2O 、CO2、TFe2O3、Ag、As、Au、B、Ba、Be、Bi、Cd、Cl、Co、Cr、Cs、Cu、F、Ga、Ge、Hf、Hg、Li、Mn、Mo、Nb、Ni、P、Pb、Rb、S、Sb、Sc、Se、Sn、Sr、Ta、Th、Ti、Tl、U、V、W、Zn、Zr、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu和Y等近70种化学元素和成分的丰度,探讨了不同构造单元花岗岩类岩石的岩石化学特征和微量元素丰度的特征及其区域分布。     

Geochemical syntheses among the cratonic,off-cratonic and orogenic garnet peridotites and their tectonic implications

Garnet-bearing mantle peridotites, occurring as either xenoliths in volcanic rocks or lenses/massifs in high-pressure and ultrahigh-pressure terrenes within orogens, preserve a record of deep lithospheric mantle processes. The garnet peridotite xenoliths record chemical equilibrium conditions of garnet-bearing mineral assemblage at temperatures (T) ranging from ~700 to 1,400°C and pressures (P) > 1.6–8.9 GPa, corresponding to depths of ~52–270 km. A characteristic mineral paragenesis includes Cr-bearing pyropic garnet (64–86 mol% pyrope; 0–10 wt% Cr₂O₃), Cr-rich diopside (0.5–3.5 wt% Cr₂O₃), Al-poor orthopyroxene (0–5 wt% Al₂O₃), high-Cr spinel (Cr/(Cr + Al) × 100 atomic ratio = 2–86) and olivine (88–94 mol% forsterite). In some cases, partial melting, re-equilibration involving garnet-breakdown, deformation, and mantle metasomatism by kimberlitic and/or carbonatitic melt percolations are documented. Isotope model ages of Archean and Proterozoic are ubiquitous, but Phanerozoic model ages are less common. In contrast, the orogenic peridotites were subjected to ultrahigh-pressure (UHP) metamorphism at temperature ranging from ~700 to 950°C and pressure >3.5–5.0 GPa, corresponding to depths of >110–150 km. The petrologic comparisons between 231 garnet peridotite xenoliths and 198 orogenic garnet peridotites revealed that (1) bulk-rock REE (rare earth element) concentrations in xenoliths are relatively high, (2) clinopyroxene and garnet in orogenic garnet peridotites show a highly fractionated REE pattern and Ce-negative anomaly, respectively, (3) Fo contents of olivines for off-cratonic xenolith are in turn lower than those of orogenic garnet and cratonic xenolith but mg-number of garnet for orogenic is less than that of off-cratonic and on-cratonic xenolith, (4) Al₂O₃, Cr₂O₃, CaO and Cr# of pyroxenes and chemical compositions of whole rocks are very different between these garnet peridotites, (5) orogenic garnet peridotites are characterized by low T and high P, off-cratonic by high T and low P, and cratonic by medium T and high P and (6) garnet peridotite xenoliths are of Archean or Proterozoic origin, whereas most of orogenic garnet peridotites are of Phanerozoic origin. Taking account of tectonic settings, a new orogenic garnet peridotite exhumation model, crust-mantle material mixing process, is proposed. The composition of lithospheric mantle is additionally constrained by comparisons and compiling of the off-cratonic, on-cratonic and orogenic garnet peridotite.     

北山造山带早泥盆世埃达克岩的发现及地质意义

北山造山带位于中亚巨型造山带南缘,是剖析中亚造山带南缘增生构造过程的关键地区之一,古亚洲洋闭合时间存在较大争议,聚焦于泥盆纪古亚洲洋仍在俯冲还是已经闭合.作者在北山造山带南缘黑山头一带首次识别出具典型埃达克岩特征的中酸性侵入体,对其进行了岩石地球化学和锆石U-Pb年代学研究.黑山头岩体中花岗闪长岩LA-ICP-MS锆石...     

Distribution and geochemical features of Hercynian-Indosinian granitoids in southeastern China

The tectonic patterns of the Hercynian-Indosinian cycle in southeastern China can be divided into two types. The first type is the Hercynian-Indosinian eugeosynclinal system, which is situated on the outer side of the Caledonian uplift belts. The second type is the Hercynian-Indosinian fault depression zone or superimposed basin system, which is developed on the basement formed by the Caledonian orogenic movement. There are two genetically different series of granitoids corresponding to two tectonic settings in the Hercynian-Indosinian tectonic regime of southeastern China. Among the transformation-series batholiths one of the largest in the Qinzhou Gulf geosyncline is known as the Darongshan granite (NE-extending) with an outcrop area of about 7000 km². The age of emplacement determined by whole-rock Rb-Sr isochron method ranges from 223 to 263 m.y., corresponding to late Permian, with higher Sr inital ratios (0.7179–0.7274). The granite is chemically rich in K₂O but poor in Na₂O with the atomic Na/K ratio<1.0 and the mole ratio Al₂O₃/(Na₂O + K₂O + CaO) > 1.0. K-feldsparg are usually predominated by medium to maximum microclines with a higher degree of Al-Si ordering characterized by the concentration of Al in T₁ sites of the feldspars (t₁ (o) = 0.57–0.99). Biotites are often rich in Fe but poor in Mg, belonging to Fe-biotite or siderophyllite, with a lower MF value (Mg/(Mg + Fe⁺³ +Fe²⁺ +Mn)), normally <0.4, and a lower Fe₃₊/Fe²⁺ ratio of 0.03-0.02 in their octahedron layers. This fact indicates that the oxidation degree of iron is relatively low in the transformation-series granites as compared with the syntexis-series granitoids. Granitic batholiths of the syntexis series distributed along the fault belts in the Hercynian depressions are usually more mafic, meta-aluminous granodiorites and smaller in size than those of the transformation series, with an outcrop area of 1–200 km₂. The Taiping granodiorite, for instance, is situated on the southern side of the Lower Yangtze River depression. It was emplaced 223 m.y. ago as dated by whole-rock Rb-Sr isochron method, with an initial Sr ratio of 0.706. Petrochemically, it is characterized by Na/K > 1.0 (1.31), mole Al₂O₃/(Na₂O + K₂O + CaO) < 1.0(0.95) and high Fe₂O₃/(Fe₂O₃ + FeO)(0.47), evidently differing from the transformation-series granites. K-feldspars are predominated by orthoclase with a lower degree of Si-Al ordering (t₁ (o) = t₁(m) = 0.30). Biotites are commonly rich in Mg in their octahedron layers (MF = 0.42–0.50) with higher Fe³⁺/Fe²⁺ ratios (0.36-0.51), indicating their formation under higher oxygen fugacity conditions. All this goes to prove that the syntexis-series granitoids were probably derived from mafic igneous or metamorphic source rocks in the lower crust.     

Activity variations attending tungsten skarn formation,Pine Creek,California

An integrated geochemical analysis of the well-exposed Pine Creek, California tungsten skarn deposit has been undertaken to evaluate changes in chemical gradients across various lithologies. Thermodynamic calculations using available experimental and thermodynamic data allow limits to be assigned to the activities of important chemical components in the metasomatic environment. Quantifiable changes in “non-volatile” component activites (CaO, MgO, Al₂O₃, Fe₂O₃, WO₃) and in fugacities (O₂, F₂) have been traced across the system. The activities of Al₂O₃, Fe₂O₃ and WO₃ generally increase from the marble (<10², <10⁻⁶, <10⁻⁵ respectively), through the outer skarn zone and into the massive garnet skarn (10^−1.7±0.3, 10^−3.4±0.4, 10^−4.8±0.1) While CaO and MgO activities decrease for the same traverse from 10⁻⁵ and 10^−2.1±1 respectively, to <10^−5.7 and <10⁻³. Calculated oxygen fugacities are 10^−23.5+1.0 at T=800 K (527° C), about one log unit below QFM, and more reducing than that required by Mt-Py-Po. The high variance of the garnet-pyroxene-quartz assemblages adds sufficient uncertainty to the calculated activities for individual specimens that only the large-scale trends survive the small-scale scatter. None of the chemical variables emerge as major independent or controlling factors for the mineralogy or phase compositions. Changes in the activity of one component may be offset by compensatory changes in another resulting in an environment that, while different from Pine Creek, could still host scheelite mineralization. Mass balance calculations indicate that the exposed endoskarn cannot have supplied the necessary chemical components to convert the country rock to skarn.     

From the green color of eskolaite to the red color of ruby: an X-ray absorption spectroscopy study

The best known cause for colors in insulating minerals is due to transition metal ions as impurities. As an example, Cr³⁺ is responsible for the red color of ruby (α-Al₂O₃:Cr³⁺) and the green color of eskolaite (α-Cr₂O₃). Using X-ray absorption measurements, we connect the colors of the Cr _x Al_2−x O₃ series with the structural and electronic local environment around Cr. UV–VIS electronic parameters, such as the crystal field and the Racah parameter B, are related to those deduced from the analysis of the isotropic and XMCD spectra at the Cr L_2,3-edges in Cr_0.07Al_1.93O₃ and eskolaite. The Cr–O bond lengths are extracted by EXAFS at the Cr K-edge in the whole Cr _x Al_2−x O₃ (0.07≤x< 2) solid solution series. The variation of the mean Cr–O distance between Cr_0.07Al_1.93O₃ and α-Cr₂O₃ is evaluated to be 0.01₅ Å (≈1%). The variation of the crystal field in the Cr _x Al_2−x O₃ series is discussed in relation with the variation of the averaged Cr–O distances.     

Interaction of model F-bearing silicic melt with chloride fluid,uraninite, and columbite at 750°C and 1000–2000 bar and its implications for estimation of the ore-forming capability of the upper crustal magma chamber beneath the Strel’tsovka caldera,eastern Transbaikalia

The experimental study of an F-bearing silicic melt—U, Nb, Ta minerals—chloride-fluoride fluid system is focused on ascertaining the origin of uranium deposits spatially related to intraplate silicic volcanism. The first series of experiments on uranium solubility in silicic melts close in composition to ore-bearing rhyolite of the unique Strel’tsovka Mo-U ore field has been performed in order to determine more precisely the ore genesis. As starting solid phases, model homogeneous glass of the chemical composition (wt %) 72.18 SiO₂, 12.19 Al₂O₃, 1.02 FeO, 0.20 MgO, 0.33 CaO, 4.78 Na₂O, 3.82 K₂O, 1.44 Li₂O, and 2.4 F (LiF, NaF, KF, CaF₂, MgF₂); synthetic UO₂ and UO₃·0.33H₂O; and natural columbite were used. The starting solutions contained 1.0 m Cl and 10⁻² m F. The runs were conducted in a gas vessel at a pressure of 1000 bar and in a high-pressure hydrothermal vessel at 2000 bar. The O₂ (H₂) fugacity was set by Ni-NiO, Co-CoO, Fe₃O₄-Fe₂O₃, and Cu-Cu₂O buffers. The equilibrium between melt and solution for major elements is reached during the first day, whereas 5–7 days are required for ore elements (U, Nb, Ta) to come into equilibrium. The solubility of Nb and especially Ta in Cl-F solutions equilibrated with F-bearing melt is extremely low. The solubility of U is much higher (10⁻⁴−10⁻⁵ mol/kg H₂O). The energy dispersive spectroscopy of run products allowed us to establish that columbite dissolved incongruently with formation of U- and F-bearing pyrochlores. The performed experiments have shown that a silicic melt close to the rhyolitic magma of the Strel’tsovka caldera in composition is not able to generate postmagmatic ore-forming solutions containing more than 10⁻⁶−10⁻⁵ mol U/kg H₂O under the relatively low pressure necessary for the existence of the first type of fluid. The amount of uranium that could have precipitated from this fluid in the zone of ore deposition is estimated at 216–9000 t. This estimate is two orders of magnitude lower than the total uranium resources of the deposits localized in the Strel’tsovka caldera. Thus, the upper crustal silicic magma chamber hardly was a source of uranium for Mo-U deposits of the Strel’tsovka ore field.     

北祁连造山带西段车路沟岩体U-Pb年代学、地球化学特征及岩石成因

车路沟岩体位于北祁连造山带最西端,岩石类型以英云闪长玢岩和闪长玢岩为主。本次对英云闪长玢岩进行U-Pb年代学研究,获得加权平均年龄为(462.1±3.8)Ma,表明岩体形成于中奥陶世。岩石地球化学分析结果显示,英云闪长玢岩中SiO_2含量60.37%～66.73%,Al_2O_3含量15.65%～16.45%,Na_2O/K_2O值7.47～9.96,A/CNK为0.90～1.00,属中酸性岩系列,显示相对富钠、低钾的特征, A/CNK=0.90～1.00,属于准铝质低钾钙碱性系列;稀土总量较低(33.40×10~(-6)～39.27×10~(-6)),LREE/HREE值为3.95～6.51,在稀土元素配分图解上呈现出右倾特征;δEu值1.23～1.49之间,呈现Eu呈正异常特征;在微量元素原始地幔标准化图解上,显示富集Ba、Sr,亏损Nb、Ti、Yb高场强元素的特征。对车路沟岩体地质、地球化学特征与产出背景的全面分析,认为其为奥陶纪祁连洋持续向华北板块俯冲,诱使俯冲洋壳部分熔融形成的埃达克岩。     

Hydrothermal synthesis of pumpellyite–okhotskite series minerals

Summary ?Hydrothermal experiments to synthesize pumpellyite group minerals of the pumpellyite–okhotskite series and to investigate their stability have been carried out at 200, 300 and 400 MPa P _fluid and 250–500 °C by using cold-seal pressure vessels and solid buffers of MnO₂–Mn₂O₃, Cu₂O–CuO and Cu₂O–Cu buffer assemblages. Okhotskite and pumpellyite rich in the okhotskite component crystallized from an oxide mixture starting material of Ca₄MgMn³⁺ ₃Al₂Si₆O_24.5-oxide+excess H₂O at P _fluid of 200, 300 and 400 MPa and temperatures of 300 and 400 °C. However, a single phase of okhotskite was not produced, and associated piemontite, hausmannite, wollastonite, clinopyroxene, corundum, braunite–neltnerite solid solution and alleghanyite also formed. Mn-pumpellyite of the okhotskite–pumpellyite join occurs as aggregates of needle crystals, rounded grains or flaky crystals. Chemical compositions are variable and range from pumpellyite-(Mn²⁺) to okhotskite: 31–36 SiO₂, 13–21 Al₂O₃, 12–25 total Mn₂O₃, 0.6–4 MgO and 20–24 wt.% CaO. Reconnaissance experiments using a starting material of synthetic Ca₂Mn³⁺Al₂Si₃O₁₂(OH)-piemontite at 300 MPa and temperatures of 250, 300, 400 and 500 °C indicate that Mn-rich pumpellyite can crystallize from piemontite at lower temperatures than the stability field of piemontite. The Mn-rich pumpellyite was accompanied by garnet, wollastonite and alleghanyite. The chemical compositions of the Mn-pumpellyites are 32–36 SiO₂, 18–27 Al₂O₃, 8–18 total Mn₂O₃ and 20–23 wt.% CaO. This study shows that the stability fields of piemontite, piemontite+Mn-pumpellyite, and Mn-pumpellyite range in this order with decreasing temperature under high fO₂ conditions. The maximum stability temperature of Mn-rich pumpellyite lies between 400 and 500 °C at 200–400 MPa in high fO₂ conditions. Received March 3, 2000; revised version accepted December 28, 2001     

The structure of sodium tetrasilicate glass from neutron diffraction, reverse Monte Carlo simulations and Raman spectroscopy

The reverse Monte Carlo (RMC) method was used for modelling the three-dimensional structure of sodium tetrasilicate glass (Na₂Si₄O₉, NS4). Neutron diffraction data over a large momentum transfer range and nuclear magnetic resonance results (Q-species distribution) as well as chemical bonding considerations have been used to constrain the RMC simulations. Very good agreement with the experimental structure factor was achieved. The three-dimensional model is analysed in terms of partial pair distribution functions, bond-angle distributions, short-range order (SRO) clusters and ring statistics. The average Si–O–Si bridging angle is different for the different Qⁱ–Q^j units. The effect of different Q species on the network connectivity is analysed by comparison with statistical SRO distributions. While the Q² species are randomly distributed, a high preference for the formation of Q⁴–Q⁴ units in three-membered rings is found. This explains why during the initial stages of hydration of NS4 glass, Si–OH groups are preferentially formed by breaking Q⁴–Q⁴ linkages. The RMC model also provides an independent test for the assignment of bands in the Si–O stretching region of the Raman spectrum. It is shown that the bands at about 1050 and 1100 cm⁻¹ are probably due to Q³ units surrounded by different numbers of Q⁴ units. Received: 7 April 1997 / Revised, accepted: 5 July 1997     

华北克拉通新太古代板块俯冲作用:来自山西云中山地区变质高镁火成岩组合的证据

在华北克拉通中部的山西云中山地区,新太古代花岗闪长质片麻岩中存在一些超镁铁质岩-镁铁质岩块及由斜长角闪岩、角闪变粒岩、石英岩和石榴夕线黑云片岩等岩石类型构成的变质表壳岩残片,其中的超镁铁质-镁铁质岩、斜长角闪岩和角闪变粒岩构成一套高镁火成岩组合。超镁铁质岩已变质为橄榄绿泥阳起片岩等岩石类型,呈变余斑状结构,橄榄石斑晶仍有保存;岩石SiO_2含量为39.22%～44.99%,Al_2O_3为8.82%～13.47%,Mg O为19.24%～22.13%,Na_2O+K_2O=0.71%～1.11%,CaO为5.75%～8.42%;Al_2O_3/TiO_2=14.8～17.4,CaO/Al_2O_3=0.60～0.84;化学成分上与科马提岩有一定的相似性。与之紧密伴生的斜长角闪岩也具有高镁特征,Mg O含量为11.28%～15.09%,铝、硅和碱质均偏低,具正铕异常,显示堆晶辉长岩的特征。非高镁斜长角闪岩有相对高的铝、硅和碱质,其原岩应为钙碱性玄武岩。角闪变粒岩样品的SiO_2含量为54.21%～55.71%,Al_2O_3为14.24%～15.49%,Mg O为6.26%～8.28%,Fe OT/Mg O=1.11～1.58,高钠低钾,Na_2O+K_2O=3.7%～4.78%,Na_2O/K_2O=5.15%～13.13,Mg#=53.0～61.5,属于高镁安山岩。由超镁铁质质岩-斜长角闪岩-角闪变粒岩构成的变质高镁火山岩组合具有钙碱性系列趋势。超镁铁质岩稀土元素含量总量较低,具有轻稀土富集和重稀土亏损的稀土型式;斜长角闪岩与超镁铁质岩比较,除富集大离子亲石元素和Cr、Ni明显较低外,具有相似的微量元素图谱形态。三种岩石类型在微量元素蛛网图上均显示出Ta、Nb、Ti负异常和Pb正异常。野外产状和岩石地球化学特征表明超镁铁质岩和高镁斜长角闪岩属于阿拉斯加型杂岩体,角闪变粒岩属于赞岐岩质高镁安山岩。在Zr/Nb-Nb/Th和Nb/Y-Zr/Y构造环境判别图解上显示出与俯冲相关的演化趋势,在Hf-Th-Ta、Nb/La-(La/Sm)N和Th/Yb-Nb/Yb图解上也落在岛弧钙碱性岩石区域。以上特征表明高镁火成岩组合形成于与板块俯冲相关的岛弧构造背景。野外地质关系和锆石U-Pb年龄限定高镁火成岩组合形成时代在～2.5Ga。云中山地区阿拉斯加型镁铁质-超镁铁质杂岩与赞岐岩质高镁安山岩共生,表明该地区存在新太古代的板块俯冲作用,为太古宙存在板块构造机制提供了新证据。     

Chemical composition and species attribution of tourmalines from a rare-metal pegmatite vein with scapolite, Sangilen Upland, Tuva

A detailed study of the chemical composition and substitutions in calcium tourmalines from a scapolite-bearing rare-metal pegmatite vein from the Sol’bel’der River basin has shown that their species attribution is determined by occupancy of octahedral site Y. The composition of the yellow tourmaline most abundant in the central part of the pegmatite bodyis rather constant and characterized by the ideal formula Ca(Mg₂Li)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃F. Variations in the chemical composition of zonal tourmaline crystals from the contact part of the pegmatite are controlled by abrupt change in the chemical medium during their formation. The yellow cores of these crystals are close in composition to tourmaline from the central part of the pegmatite vein. The Mg content abruptly decreases toward the crystal margin: Mg²⁺ → Fe²⁺, 2Mg²⁺ → Li⁺ + Al³⁺, and Mg²⁺ + OH → Al³⁺ + O²⁻. The composition of dark green marginal zones in tourmaline is characterized by the ideal formula Ca(Al_1.5Li_1.5)Al₆(Si₆O₁₈)(BO₃)₃ (OH₂O)(F). The results indicate specific formation conditions of pegmatite. The crystallochemical formulas of the studied tourmalines allow us to regard them as new mineral species in the tourmaline group.     

Ore fluid geochemistry of the Jinlongshan Carlintype gold ore belt in Shaanxi Province, China

THEJINLONGSHANGOLDOREBELTINZHEN’ANCOUN TY,SOUTHERNSHAANXIPROVINCE,ISLOCATEDINTHEWEST ERNQINLINGGOLDPROVINCE(NO.16INFIG.1;CHEN YANJINGETAL.,2004).ITWASDISCOVEREDINTHEDEVO NIANSTRATAINTHELATE1980S).ITSGEOLOGICALSETTING ANDMETALLOGENICEVOLUTIONARESIMILARTOT…     

Thermodynamics of arsenates,selenites, and sulfates in the oxidation zone of sulfide ores: I. Thermodynamic constants at ambient conditions

Understanding and deciphering processes proceeding near the surface are among the urgent tasks of contemporary mineralogy and geochemistry, which are especially important for resolving ecological challenges and developing principles of rational environmental management. The paper presents systematized data published on thermodynamics of minerals (arsenates, sulfates, selenites, and selenates), which are formed in the weathering zone of sulfide ores, and determines approaches to quantitative physicochemical modeling of their formation conditions. Diagrams of phase and chemical equilibria (Eh-pH, diagrams of solubility) of the subsystems of the model system Fe-Cu-Zn-Pb-Co-Ni-As-Se-S-H₂O (Fe²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Pb²⁺, Ni²⁺, Co²⁺, H⁺//SeO₃²⁻, SeO₄²⁻, AsO₄³⁻, SO₄²⁻, OH⁻-H₂O) are used as a thermodynamic basis for modeling mineral-forming processes in the weathering zone of ore deposits. Seventy-two arsenates, about 70 sulfates, and 7 selenites and selenates have been identified in the framework of this system. The available published values of standard thermodynamic functions of the formation of minerals and chemical compounds are given, as well as the Pitzer equation parameters to describe the sulfate systems, which are substantially specific due to the high solubility of their components.     

阿尔金造山带青白口纪片麻状花岗岩的厘定及对Rodinia超大陆汇聚时限的制约

阿尔金造山带新元古代花岗岩的研究对探讨该地区Rodinia超大陆汇聚阶段构造演化过程具有重要意义。本文对在亚干布阳一带新厘定的青白口纪片麻状花岗岩开展了详细的岩石学、年代学和岩石地球化学研究。锆石LA-ICP-MS U-Pb年代学证据显示片麻状花岗岩结晶年龄分别为(883.0±3.3)Ma和(883.1±3.3)Ma,说明其侵位于青白口纪。地球化学结果显示,常量元素具有富硅、铝、钾和低钠、镁、钙和钛的特点,具钙碱性-高钾钙碱性、过铝质花岗岩特征。岩石轻稀土分馏较强而重稀土分馏较弱,具有明显的负Eu异常,总体呈右倾的"V"型稀土分配模式。岩石富集Rb、Th、LREE等大离子亲石元素,中等亏损Ba,强烈亏损Nb、Sr、P、Hf、Ti等高场强元素,总体特征显示了典型的壳源花岗岩的特征,其源于地壳变质砂岩部分熔融,形成于同碰撞晚期构造环境,属Rodinia超大陆汇聚阶段的产物。综合研究表明,阿尔金地区新元古代早期同碰撞型岩体的形成时代集中在871～945 Ma,限定了Rodinia超大陆汇聚时限,且在空间上构成了一条重要的岩浆岩带,是对Rodinia超大陆碰撞汇聚作用的响应。     

Florencite-(Sm)—(Sm,Nd)Al3(PO4)2(OH)6: A new mineral species of the alunite-jarosite group from the subpolar urals

Florencite-(Sm), a new mineral species of the florencite subgroup, was found in association with xenotime-(Y) in quartz veins of the Maldynyrd Range of the Subpolar Urals as thin zones within rhombohedral crystals of florencite-(Ce) with faceting by { 01[`1]1}\{ 01\bar 11\} and { 10[`1]2}\{ 10\bar 12\} . The thickness of particular florencite-(Sm) zones is 0.01–0.1 mm, and the total thickness of a series of such zones is 1–3 mm. Florencite-(Sm) is colorless and pale pink or pale yellow with white streaks; its Mohs hardness is 5.5–6.0. Its measured and calculated densities are 3.70 and 3.743 g/cm³, respectively. The mineral is transparent, nonpleochroic, and uniaxial (positive), and ω = 1.704(2) and ɛ = 1.713(2). The electron beam’s fluorescence spectrum was 592 nm (intense green luminescence of Sm³⁺) and 558 nm (yellow luminescence of Nd³⁺). The chemical composition was as follows (microprobe, average of 2 WDS, wt %): 0.62 La₂O₃, 3.29 Ce₂O₃, 1.05 Pr₂O₃, 10.31 Nd₂O₃, 12.62 Sm₂O₃, 0.41 Eu₂O₃, 2.30 Gd₂O₃, 0.13 Dy₂O₃, 0.71 SrO, 0.35 CaO, 29.89 Al₂O₃, 26.14 P₂O₅, 0.85 SO₃, 0.09 SiO₂, 88.76 in total; 10.74 H₂O (meas.). The empirical formula based on 14 oxygen atoms is (Sm_0.38Nd_0.32Gd_0.07Ce_0.10Pr_0.03La_0.02Eu_0.01Sr_0.04Ca_0.03)1.0Al_3.04(P_1.91S_0.05Si_0.01)_1.97O₁₄H_5.92. The idealized formula is (Sm,Nd)Al₃(PO₄)₂(OH)₆. Mineral is trigonal, space group R3m, a = 6.972(4), c = 16.182(7) ?, V = 681.2 ?³, Z = 3. The XRD pattern is as follows: dln (I) (hkl): 2.925 (10) (113), 1.881 (6) (303), 2.161 (5) (107), 5.65 (4) (101), and 3.479 (4) (110). The IR spectrum: 466, 510, 621, 1036, 1105, 1223, 2957, and 3374 cm⁻¹.     

Kyanoxalite,a new cancrinite-group mineral species with extraframework oxalate anion from the Lovozero alkaline pluton,Kola Peninsula

Kyanoxalite, a new member of the cancrinite group, has been identified in hydrothermally altered hyperalkaline rocks and pegmatites of the Lovozero alkaline pluton, Kola Peninsula, Russia. It was found at Mount Karnasurt (holotype) in association with nepheline, aegirine, sodalite, nosean, albite, lomonosovite, murmanite, fluorapatite, loparite, and natrolite and at Mt. Alluaiv. Kyanoxalite is transparent, ranging in color from bright light blue, greenish light blue and grayish light blue to colorless. The new mineral is brittle, with a perfect cleavage parallel to (100). Mohs hardness is 5–5.5. The measured and calculated densitiesare 2.30(1) and 2.327 g/cm³, respectively. Kyanoxalite is uniaxial, negative, ω = 1.794(1), ɛ = 1.491(1). It is pleochroic from colorless along E to light blue along O. The IR spectrum indicates the presence of oxalate anions C₂O₄²⁻ and water molecules in the absence of CO₃²⁻ Oxalate ions are confirmed by anion chromatography. The chemical composition (electron microprobe; water was determined by a modified Penfield method and carbon was determined by selective sorption from annealing products) is as follows, wt %: 19.70 Na₂O, 1.92 K₂O, 0.17 CaO, 27.41 Al₂O₃, 38.68 SiO₂, 0.64 P₂O₅, 1.05 SO₃, 3.23 C₂O₃, 8.42 H₂O; the total is 101.18. The empirical formula (Z = 1) is (Na_6.45K_0.41Ca_0.03)_Σ6.89(Si_6.53Al_5.46O₂₄)[(C₂O₄)_0.455(SO₄)_0.13(PO₄)_0.09(OH)_0.01]_Σ0.68 · 4.74H₂O. The idealized formula is Na₇(Al₅₋₆Si₆₋₇O₂₄)(C₂O₄)_0.5−1 · 5H₂O. Kyanoxalite is hexagonal, the space group is P6₃, a = 12.744(8), c = 5.213(6) -ray powder diffraction pattern are as follows, [d, [A] (I, %)(hkl)]: 6.39(44) (110), 4.73 (92) (101), 3.679 (72) (300), 3.264 (100) (211, 121), 2.760 (29) (400), 2.618 (36) (002), 2.216, (29) (302, 330). According to the X-ray single crystal study (R = 0.033), two independent C₂O₄ groups statistically occupy the sites on the axis 6₃. The new mineral is the first natural silicate with an additional organic anion and is the most hydrated member of the cancrinite group. Its name reflects the color (κɛανgoΣς is light blue in Greek) and the species-forming role of oxalate anions. The holotype is deposited at the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, registration no. 3735/1.     

钦-杭结合带南段新元古代俯冲作用:来自粤西贵子混杂岩变基性岩年代学和地球化学的证据

新元古代以来,扬子地块和华夏地块拼贴形成钦-杭结合带。粤西贵子混杂岩为揭示钦-杭结合带南段地质演化提供了一个重要的窗口。贵子混杂岩构造岩块为强烈变形-变质的变基性岩、深海硅质岩,基质为石英岩、云母片岩以及具鲍马序列富锰质硅泥质岩等。对混杂岩中变基性岩年代学和元素地球化学分析显示,锆石U-Pb年龄为948±11Ma,除少部分属低钾(拉斑)外,其余均为钙碱性系列,CIPW标准矿物成分属石英拉斑玄武岩-橄榄拉斑玄武岩组合。变基性岩具有高TiO_2(平均1.85%)、P_2O_5(平均0.21%)的特点;无Eu异常或轻微负异常,配分曲线右倾(球粒陨石标准化(La/Yb)N=2.65~3.89),大离子亲石元素(Rb、Ba、Th、U)富集,高场强元素(Nb、Zr、Hf)轻微亏损,表现为洋壳消减作用下岛弧岩浆岩特征。高的Nb(7.56×10~(-6)~16.11×10~(-6),均大于7×10~(-6))、Nb/U(18.39~25.65)、(Nb/La)N(0.76~0.94,原始地幔标准化)显示为岛弧环境富Nb玄武岩。本研究认为,云开地块出露的这套构造混杂岩,是新元古代古华南洋俯冲在钦-杭结合带南段的记录,可为该带的南东边界提供线索。     

Systematics of calcium partitioning between olivine and silicate melt: implications for melt structure and calcium content of magmatic olivines

A systematic characterization of the chemical factors that control calcium partitioning between olivine and melt in a magmatic environment was undertaken using experiments performed on compositionally simple systems (CaO-MgO-SiO₂, CaO-MgO-Al₂O₃-SiO₂, CaO-MgO-Al₂O₃-SiO₂-Cr₂O₃, CaO-MgO-Al₂O₃-SiO₂-TiO₂, CaO-MgO-Al₂O₃-SiO₂-Na₂O, CaO-MgO-Al₂O₃-SiO₂-FeO, CaO-MgO-Al₂O₃-SiO₂-FeO-Na₂O) over a wide range of temperature (1050–1530 °C) at one bar pressure. The calcium concentration of olivines is shown to be dependent not only on the forsterite content of the olivine but to a large extent on melt composition. For a fixed CaO content of the melt, these results show that the CaO concentration of olivine is strongly sensitive to the amount of alumina, alkali and ferrous iron present in the coexisting melt. Oxygen fugacity and temperature are not found directly to affect Ca partitioning. It is thus proposed that the systematic variations of the calcium content of olivine may be used as an “in-situ chemical potentiometer” of the lime activity of the melt. Based upon these data in synthetic systems, an empirical model describing Ca partitioning between olivine and melt is developed. When applied to natural olivines this model reproduces their Ca content, where melt composition is known, to within ±10% relative. The model may therefore be used to predict changes in melt composition during olivine crystallization and/or to assess whether an olivine is in equilibrium with its host magma. Finally, the wide range of Ca partitioning observed at fixed crystal composition confirms that minor element partitioning between crystal and melt cannot be predicted from the physical characteristics of the crystal alone, and that the non-ideality of the melt has to be taken into account. Received: 12 June 1998 / Accepted: 1 February 1999