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1.
“东川式“层状铜矿40Ar-39Ar成矿年龄测定 总被引：1，自引：0，他引：1
《矿物岩石地球化学通报》2001,20(4):358-359
本文采用40Ar-39真空击碎技术和阶段加热技术,测定了采自落雪矿的"东川式"层状铜矿之两个石英样品的年龄,获得了810～770
Ma的40Ar-39Ar等时线年龄,这些年龄与我们从前获得的脉状铜矿石英的年龄范围一致,再次表明晋宁-澄江期是东川铜矿的主要成矿期. 相似文献
2.
“东川式”层状铜矿~(40)Ar-~(39)Ar成矿年龄测定 总被引：3，自引：0，他引：3
本文采用40 Ar 3 9Ar真空击碎技术和阶段加热技术 ,测定了采自落雪矿的”东川式”层状铜矿之两个石英样品的年龄 ,获得了 810～ 770Ma的40 Ar 3 9Ar等时线年龄 ,这些年龄与我们从前获得的脉状铜矿石英的年龄范围一致 ,再次表明晋宁 澄江期是东川铜矿的主要成矿期。 相似文献
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采用单矿物^40Ar-^39Ar年代学方法，对河南祁雨沟爆破角砾岩型金矿的矿化蚀变矿物进行了高精度的定年研究，矿脉中钾长石的^40Ar-39Ar 年龄表明，祁雨沟金矿的主要成矿阶段发生在115－125Ma期间，成矿作用持续达10Ma。结合产人研究成果分析，区域燕山期花岗岩侵位30Ma之后祁雨沟金矿开始进入主成矿期，此时正是区域伸展构造的发育时期，深部流体活动频繁而强烈。祁雨沟金矿是中国东部金的大规模成矿作用的组成部分。 相似文献
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攀西裂谷带内超基性碱性岩和层状辉长岩^40Ar-^39Ar年龄——以鸡街、大向坪和太和岩体为例 总被引：5，自引：0，他引：5
对分布在攀西古裂谷带内的禄丰县鸡街和大向坪超基性碱性环状杂岩体中霞辉岩，以及西昌太和层状辉长岩等两类岩石进行全岩^40Ar-^39Ar坪年龄测定，结果表明鸡街岩体和大向坪岩体中霞辉岩年龄范围在214～193Ma，相当于晚三叠世，属于印支期。总体上，超基性碱性环状杂岩的侵位时间略晚于含矿辉长岩；太和层状辉长岩^40Ar-^39Ar坪年龄，由于过剩Ar等原因的扰动，使其年龄值远远高于成岩年龄。暗示全岩或辉石单矿物等不适合作为攀西地区层状辉长岩定年的对象。 相似文献
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黑龙江省东宁县金厂金矿是滨太平洋成矿域浅成低温-斑岩成矿系统中极具代表性的特大型金矿床。矿区已发现爆破角砾岩筒型、环状一放射状裂隙充填型、似层状微细脉浸染型和断控构造破碎带蚀变岩型等矿化类型。为确定成矿时间,作者应用高精度单颗粒激光熔蚀氩氩法,选择Ⅻ号破碎带蚀变岩型矿体中多金属硫化物一石英脉中石英和J-9号爆破角砾岩筒型矿体中闪锌矿进行年龄测定。获得Ⅻ号矿体石英40Ar/39Ar等时线年龄为119±5Ma（MSWD：6．3）,J-9号矿体闪锌矿40Ar/39Ar等时线年龄为129±0．8Ma（MSWD=3．7）,限定了成矿作用的上限。结合最新获得的相关成矿地质体精细年代学成果,进一步认定金厂金矿成矿时代为燕山晚期,成矿与同时代闪长玢岩一花岗闪长斑岩关系密切。金厂金矿成岩、成矿环境具备寻找富金斑岩型铜矿的有利条件,与成矿关系密切侵入岩呈岩脉、岩枝状,指示矿区剥蚀程度浅,深部还有发现斑岩型Au（cu）矿化的可能。 相似文献
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砂宝斯金矿床是大兴安岭北部唯一一个大型岩金矿床。本文应用石英真空击碎和阶段加热40Ar/39Ar定年技术,首次获得了砂宝斯金矿床的成矿年龄。石英真空击碎40Ar/39Ar定年方法获得了石英脉中原生包裹体等时线年龄为130.1±1.3 Ma;石英粉末阶段加热40Ar/39Ar定年方法获得石英脉中钾长石微晶的等时线年龄为133.1±3.5 Ma。石英脉中原生包裹体和钾长石微晶的年龄较吻合,~130 Ma代表了含金石英脉的形成年龄。砂宝斯金矿床的成矿时代为早白垩世,形成于蒙古-鄂霍茨克造山带后碰撞阶段的挤压向伸展转换期。 相似文献
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大渡河金矿田是扬子地台西南缘一个重要的金成矿集中区.对其中自金台子和三雕两个金矿床含金石英脉的石英进行了40Ar/39Ar快中子活化法同位素年龄测试,获得坪年龄分别为25.4土0.2 Ma和24.7±0.3Ma,相应的等时线年龄分别为24.1±0.1 Ma和22.9士0.1 Ma,反等时线年龄分别为23.8士0.1 Ma和23.0±0.1Ma.这些年龄数据不仅有力地证明了大渡河金矿形成于喜马拉雅构造期,也为更好地认识扬子地台西南缘金矿形成的地质构造背景、矿床成因及成矿规律,进而指导区域找矿提供了依据. 相似文献
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云南东川播卡-拖布卡地区含金石英脉的^40Ar／^39Ar年龄及其地质意义 总被引：4，自引：0，他引：4
东川播卡-拖布卡地区金矿是云南中部"康滇地轴"中、新元古界昆阳群岩石中发现的第一个金矿,位于接近三江褶皱带的扬子地块西缘.原生金矿化为含金黄铁矿石英脉、细脉、网脉和浸染状石英黄铁矿.四个不同产状的典型含金石英脉的石英的阶段加热40Ar/39Ar年龄谱为马鞍形,坪年龄值范围为59.93±0.21～42.38±0.32 Ma,最小视年龄范围59.30±4.30～41.90±1.8 Ma,与计算坪年龄加热阶段相应数据的40Ar-39Ar等时线年龄范围59.34±0.17～41.25±0.10 Ma,三者基本一致.等时线年龄计算的相关系数大于0.998,40Ar/3 6Ar初始值范围为293.17±1.40～295.2±0.43,与尼尔值一致.石英形成后没有受到后期地质作用.石英样品的坪年龄没有受到过剩氩和氩丢失的影响,可以作为石英和金矿的年龄.金矿形成于新生代第三纪古新世和始新世初的陆内拉张地质构造环境中. 相似文献
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本文采用高精度的^40Ar-^39Ar计时技术，系统地测定了滇西泸水钨锡矿床片麻状花岗岩、锡矿石和钨矿石中的白云母和石英等矿物的年龄，结合野外地质情况和岩矿薄片镜下特征，查明该矿为多期成矿，片麻状花岗岩年龄为163Ma，锡矿145Ma，钨矿有两期，分别为69Ma和39Ma。同时研制了金属超高真空碎样提氩装置，并与MM-1200质谱计系统连接，测定了钨矿石中石英的流体包裹体的^40Ar-^39Ar年龄，为矿床形成年龄测定开辟了新的实验测试途径。 相似文献
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Enthalpies of solution in 2PbO· B2O3 at 712°C have been measured for glasses in the systems albite anorthite diopside, NaAlO2-SiO2, Ca0.5AlO2-SiO2 and albite-anorthite-quartz. The systems albite-anorthite and diopside-anorthite show substantial negative enthalpies of mixing, albite-diopside shows significant positive heats of mixing. For compositions up to NaAlO2 = 0.42 (which includes the subsystem albite-silica) the system NaAlO2-SiO2 shows essentially zero heats of mixing. A negative ternary excess heat of mixing is found in the plagioclase-rich portion of the albite-anorthite-diopside system. The join Si4O8-CaAl2Si2O8 shows small but significant heats of mixing. In albite-anorthite-quartz. ternary glasses, the ternary excess enthalpy of mixing is positive.Based on available heat capacity data and appropriate consideration of the glass transition, the enthalpy of the crystal-glass transition (vitrification) is a serious underestimate of the enthalpy of the crystal-liquid transition (fusion) especially when the melting point, Tf, is many hundreds of degrees higher than the glass transition temperature, Tg. On the other hand, the same heat capacity data suggest that the enthalpies of mixing in albite-anorthite-diopside liquids are calculated to be quite similar to those in the glasses. The enthalpies of mixing observed in general support the structural models proposed by Taylor and Brown (1979a, b) and others for the structure of aluminosilicate glasses. 相似文献
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Enthalpies of solution in 2PbO · B2O3 at 981 K have been measured for glasses in the system albite-orthoclase-silica and along the join Na1.6Al1.6Si2.4O8-K1.6Al1.6Si2.4O8. The join KAlSi3O8-Si4O8 shows zero heat of mixing similar to that found previously for NaAlSi3O8-Si4O8 glasses. Albite-orthoclase glasses show negative heats of mixing symmetric about Ab50Or50 (Wn = ? 2.4 ± 0.8 kcal). Negative heats of (Na, K) mixing are also found at Ternary excess enthalpies of mixing in the glassy system Ab-Or-4Q are positive but rarely exceed 1 kcal mol?1.Using earlier studies of the thermodynamic properties of the crystals, the present calorimetric data and the “two-lattice” entropy model, the albite-orthoclase phase diagram is calculated in good agreement with experimental data. Attempts to calculate albite-silica and orthoclase-silica phase diagrams reveal complexities probably related to significant (but unknown) mutual solid solubility between cristobalite and alkali feldspar and to the very small heat and entropy of fusion of SiO2. 相似文献
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An end member of the tourmaline series with a structural formula □(Mg2Al)Al6(BO3)3[Si6O18](OH)4 has been synthesized in the system MgO-Al2O3-B2O3-SiO2-H2O where it represents the only phase with a tourmaline structure. Our experiments provide no evidence for the substitutions Al → Mg + H, Mg → 2H, B + H → Si, and AlAl → MgSi and we were not able to synthesize a phase “Mg-aluminobuergerite” characterized by Mg in the (3a)-site and a strong (OH)-deficiency reported by Rosenberg and Foit (1975). The alkali-free tourmaline has a vacant (3a)-site and is related to dravite by the □ + Al for Na + Mg substitution. It is stable from at least 300°C to about 800°C at low fluid pressures and 100% excess B2O3, and can be synthesized up to a pressure of 20 kbars. At higher temperatures the tourmaline decomposes into grandidierite or a boron-bearing phase possibly related to mullite (“B-mullite”), quartz, and unidentified solid phases, or the tourmaline melts incongruently into corundum + liquid, depending on pressure. In the absence of excess B2O3 tourmaline stability is lowered by about 60°C. Tourmaline may coexist with the other MgO-Al2O3-B2O3-SiO2-H2O phases forsterite, enstatite, chlorite, talc, quartz, grandidierite, corundum, spinel, “B-mullite,” cordierite, and sinhalite depending on the prevailing PTX-conditions.The (3a)-vacant tourmaline has the space group R3m with , , and . However, these values vary at room temperature with the pressure-temperature conditions of synthesis by , , and , probably as a result of MgAl order/disorder relations in the octahedral positions. Despite these variations intensity calculations support the assumed structural formula. Refractive indices are no = 1.631(2), nE = 1.610(2), Δn = 0.021. The infrared spectrum is intermediate between those of dravite and elbaite. The common alkali and calcium deficiencies of natural tourmalines may at least partly be explained by miscibilities towards (3a)-vacant end members. The apparent absence of (3a)-vacant tourmaline in nature is probably due to the lack of fluids that carry boron but no Na or Ca. 相似文献
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Richard L. Hervig Derry Scott Alexandra Navrotsky 《Geochimica et cosmochimica acta》1985,49(7):1497-1501
Enthalpies of solution in 2PbO · B2O3 at 974 K have been measured for glasses along the joins Ca2Si2O6 (Wo)-Mg2Si2O6 (En) and Mg2Si2O6-MgAl2SiO6 (MgTs). Heats of mixing are symmetric and negative for Wo-En with WH = ?31.0 ± 3.6 kJ mol?. Negative heats of mixing were also found for the En-MgTs glasses (WH = ?33.4 ± 3.7 kJ mol?).Enthalpies of vitrification of pyroxenes and pyroxenoids generally increase with decreasing alumina content and with decreasing basicity of the divalent cation.Heats of mixing along several glassy joins show systematic trends. When only non-tetrahedral cations mix (outside the aluminosilicate framework), small exothermic heats of mixing are seen. When both nontetrahedral and framework cations mix (on separate sublattices, presumably), the enthalpies of mixing are substantially more negative. Maximum enthalpy stabilization near compositions with Al/Si ≈ 1 is suggested. 相似文献
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Five hundred eighty-five viscosity measurements on 40 melt compositions from the ternary system CaMgSi2O6 (Di)-CaAl2Si2O8 (An)-NaAlSi3O8 (Ab) have been compiled to create an experimental database spanning a wide range of temperatures (660-2175°C). The melts within this ternary system show near-Arrhenian to strongly non-Arrhenian properties, and in this regard are comparable to natural melts. The database is used to produce a chemical model for the compositional and temperature dependence of melt viscosity in the Di-An-Ab system. We use the Vogel-Fulcher-Tammann equation (VFT: log η = A + B/(T − C)) to account for the temperature dependence of melt viscosity. We also assume that all silicate melts converge to a common viscosity at high temperature. Thus, A is independent of composition, and all compositional dependence resides in the parameters B and C. The best estimate for A is −5.06, which implies a high-temperature limit to viscosity of 10-5.06 Pa s. The compositional dependence of B and C is expressed by 12 coefficients (bi=1,2.6, cj=1,2..6) representing linear (e.g., bi=1:3) and higher order, nonlinear (e.g., bi=4:6) contributions. Our results suggest a near-linear compositional dependence for B (<10% nonlinear) and C (<7% nonlinear). We use the model to predict model VFT functions and to demonstrate the systematic variations in viscosity due to changes in melt composition. Despite the near linear compositional dependence of B and C, the model reproduces the pronounced nonlinearities shown by the original data, including the crossing of VFT functions for different melt compositions. We also calculate values of Tg for melts across the Di-An-Ab ternary system and show that intermediate melt compositions have Tg values that are depressed by up to 100°C relative to the end-members Di-An-Ab. Our non-Arrhenian viscosity model accurately reproduces the original database, allows for continuous variations in rheological properties, and has a demonstrated capacity for extrapolation beyond the original data. 相似文献
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Guy L. Hovis 《Geochimica et cosmochimica acta》1984,48(3):523-525
Glasses in the systems NaAlSi3O8-KAlSi3O8 and NaAlSi3O8-Si4O8 have been studied by means of hydrofluoric acid solution calorimetry at 50°C. Results indicate small negative enthalpies of mixing in the former system and small positive departures from ideality in the latter. 相似文献
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R.C. Newton T.V. Charlu P.A.M. Anderson O.J. Kleppa 《Geochimica et cosmochimica acta》1979,43(1):55-60
Enthalpies of solution of synthetic clinopyroxenes on the join CaMgSi2O6-Mg2Si2O6 have been measured in a melt of composition Pb2B2O5 at 970 K. Most of the measurements were made on samples crystallized at 1600°–1700°C and 30 kbar pressure, which covered the range 0–78 mole per cent Mg2Si2O6, and whose X-ray patterns could be satisfactorily indexed on the diopside (C2/c) structure. For the reaction: Mg2Si2O6→-Mg2Si2O6 enstatite diopside the present data, in conjunction with previous and new measurements on Mg2Si2O6 enstatite, determine ΔH° ~ 2 kcal and WH (regular solution parameter) ~ 7 kcal. These values are in good agreement with those deduced by Saxena and Nehru (1975) from a study of high temperature, high pressure phase equilibrium data under the assumption that the excess entropy of mixing is small, but, in light of the recent theoretical treatment of Navrotsky and Loucks (1977, Phys. Chem. Min.1, 109–127), the meanings of these parameters may be ambiguous.Heat of solution measurements on Ca-rich binary diopsides made by annealing glasses at 1358°C in air gave slighter higher values than the higher temperature high pressure samples. This may be evidence for some (Ca, Mg) disorder of the sort postulated by Navrotsky and Loucks (1977, Phys. Chem. Min.1, 109–127), although no differences in heat of solution dependent on synthesis temperature in the range 1350°–1700°C could be found in stoichiometric CaMgSi2O6. 相似文献
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Charles A. Geiger Edgar Dachs Gilberto Artioli 《Geochimica et cosmochimica acta》2010,74(18):5202-5215
Armenite, ideal formula BaCa2Al6Si9O30·2H2O, and its dehydrated analog BaCa2Al6Si9O30 and epididymite, ideal formula Na2Be2Si6O15·H2O, and its dehydrated analog Na2Be2Si6O15 were studied by low-temperature relaxation calorimetry between 5 and 300 K to determine the heat capacity, Cp, behavior of their confined H2O. Differential thermal analysis and thermogravimetry measurements, FTIR spectroscopy, electron microprobe analysis and powder Rietveld refinements were undertaken to characterize the phases and the local environment around the H2O molecule.The determined structural formula for armenite is Ba0.88(0.01)Ca1.99(0.02)Na0.04(0.01)Al5.89(0.03)Si9.12(0.02)O30·2H2O and for epididymite Na1.88(0.03)K0.05(0.004)Na0.01(0.004)Be2.02(0.008)Si6.00(0.01)O15·H2O. The infrared (IR) spectra give information on the nature of the H2O molecules in the natural phases via their H2O stretching and bending vibrations, which in the case of epididymite only could be assigned. The powder X-ray diffraction data show that armenite and its dehydrated analog have similar structures, whereas in the case of epididymite there are structural differences between the natural and dehydrated phases. This is also reflected in the lattice IR mode behavior, as observed for the natural phases and the H2O-free phases. The standard entropy at 298 K for armenite is S° = 795.7 ± 6.2 J/mol K and its dehydrated analog is S° = 737.0 ± 6.2 J/mol K. For epididymite S° = 425.7 ± 4.1 J/mol K was obtained and its dehydrated analog has S° = 372.5 ± 5.0 J/mol K. The heat capacity and entropy of dehydration at 298 K are Δ = 3.4 J/mol K and ΔSrxn = 319.1 J/mol K and Δ = −14.3 J/mol K and ΔSrxn = 135.7 J/mol K for armenite and epididymite, respectively. The H2O molecules in both phases appear to be ordered. They are held in place via an ion-dipole interaction between the H2O molecule and a Ca cation in the case of armenite and a Na cation in epididymite and through hydrogen-bonding between the H2O molecule and oxygen atoms of the respective silicate frameworks. Of the three different H2O phases ice, liquid water and steam, the Cp behavior of confined H2O in both armenite and epididymite is most similar to that of ice, but there are differences between the two silicates and from the Cp behavior of ice. Hydrogen-bonding behavior and its relation to the entropy of confined H2O at 298 K is analyzed for various microporous silicates.The entropy of confined H2O at 298 K in various silicates increases approximately linearly with increasing average wavenumber of the OH-stretching vibrations. The interpretation is that decreased hydrogen-bonding strength between a H2O molecule and the silicate framework, as well as weak ion-dipole interactions, results in increased entropy of H2O. This results in increased amplitudes of external H2O vibrations, especially translations of the molecule, and they contribute strongly to the entropy of confined H2O at T < 298 K. 相似文献