应用X射线衍射-激光拉曼光谱-电子探针等分析测试技术研究旬阳朱砂玉的矿物学特征

近年来外观形似鸡血石的红色朱砂玉备受关注,其中吉林、贵州、青海等地这种红色岩石已有矿物成分、岩性等相关方面的研究。本文利用常规宝石常数测定手段、偏光显微镜、X射线粉晶衍射仪、激光拉曼光谱仪、电子探针等分析测试技术,对陕西旬阳朱砂玉的矿物学和宝石学特征进行了研究。结果表明,该产地朱砂玉的矿物成分以石英、辰砂为主,含有少量的方解石、白云石、重晶石、黄铁矿;其中主要矿物成分辰砂的颜色随铁含量的增加而逐渐加深;矿物结构以碎屑结构、粒状变晶结构、穿插交代结构为主。根据矿物成分以及矿床成因的研究分析,初步认为陕西旬阳朱砂玉属于沉积-热液-强烈改造型矿床。该地区的朱砂玉与鸡血石的相似之处在于矿物的主要成分都含有辰砂,致使外观品质上具有一定的相似性,但具体矿床成因以及矿物成分有着明显的差别:旬阳朱砂玉产于沉积-热液-强烈改造型矿床中,其“地”主要矿物成分为石英岩,“血”为辰砂;而浙江昌化和内蒙古巴林鸡血石均产于中生代交代蚀变酸性火山岩的次级断裂小构造中,其“地”主要为地开石、高岭石、叶腊石,“血”为辰砂。此次研究采用多种分析测试手段为旬阳朱砂玉与鸡血石的鉴别提供了可靠的依据。     

Fluid Inclusion and Stable Isotope Studies at Don Sixto,a Precious Metal Low Sulfidation Deposit in Mendoza Province,Argentina

The Don Sixto mining area in Mendoza province, central‐western Argentina, contains an epithermal low sulfidation Au–Ag deposit. It is a small deposit (～4 km²), with a gold resource of 36 t. In Don Sixto, ore minerals are disseminated in the hydrothermal quartz veins and hydrothermally altered volcanic‐pyroclastic rock units of Permian–Triassic age. On the basis of the texture, ore mineral paragenesis and cross cutting relationship of gangue minerals, seven stages of mineralization were recognized and described. The first six stages are characterized by quartz veins with minor amounts of base metal minerals and the last stage is represented by fluorite veins with minimal quantities of base metal minerals; the precious metal mineralization is mainly related to the fourth stage. The hydrothermal veins exhibit mainly massive, crustiform and comb infilling textures; the presence of bladed quartz replacement textures and quartz veins with adularia crystals are indicative of boiling processes in the system. Fluid inclusion and complementary stable isotope studies were performed in quartz, fluorite, and pyrite samples from the vein systems. The microthermometric data were obtained from primary, biphasic (liquid‐vapor) fluid inclusion assemblages in quartz and fluorite. The maximum values for salinity and homogenization temperature (T_h) came from the stage IV where quartz with petrographic evidence of boiling has average values of 4.96 wt% NaCl_equiv. and 286.9°C respectively. The lower values are related to the last stage of mineralization, where the fluid inclusions in fluorite have average salinities of 1.05 wt% NaCl_equiv. and average homogenization temperatures of 173.1°C. The oxygen and sulfur isotopic fractionation was analyzed in quartz and pyrite. The calculated isotopic fractionation for oxygen in the hydrothermal fluid is in the range of δ¹⁸O_H2O = ?6.92 up to ?3.08‰, which indicates dominance of a meteoric source for the water, while sulfur reaches δ³⁴S_H2S = 1.09‰, which could be reflecting a possible magmatic, or even a mixed source.     

LNAPL 污染土壤介电性质的实验研究——-以石英砂为例

为研究轻非水相液体污染土壤的介电性质,在实验室条件下,利用石英砂( 粒径0. 106 ～ 0. 212 mm) 、柴油和水的混合物模拟LNAPL 污染土壤,采用开口同轴探头法利用高频电磁波( 200 MHz ～ 3 GHz) 在污染土壤中的反射获得介电常数,并分析土壤中油水体积含量变化与相对介电常数的变化规律。实验结果表明: 非饱和状态下石英砂的相对介电常数随着体积含水量和含油量的增大而增大,达到饱和状态后体积含油量的增加对相对介电常的影响不明显; 被污染的非饱和状态的砂样在放置过程中,相对介电常数随着放置时间的延长呈现先增大最后趋于稳定的变化趋势。     

桂西北地区石英斑岩脉白云母40Ar/39Ar 年龄及其地质意义

华南西部右江褶皱带内部燕山晚期岩浆岩主要为成群分布的基性- 超基性岩墙群和超酸性岩脉带。本文对桂西北巴
马-凤山-凌云一带的石英斑岩脉进行了斑晶白云母40Ar/39Ar 法测年,获得凤山弄黄北东向岩脉的40Ar/39Ar 坪年龄为（95.59
±0.68）Ma,相应的等时线年龄为（95.0±1.0）Ma;巴马北西向岩脉的坪年龄为（96.54±0.70）Ma,相应的等时线年龄为
（95.91±1.1）Ma。上述年龄代表了岩脉的侵位年龄。这些年龄数据进一步证明右江褶皱带及其周缘燕山期岩浆活动集中于
80~100 Ma 之间,暗示该区晚白垩世发生了大规模的岩石圈伸展减薄事件。华南西部晚白垩世花岗质岩浆活动与大规模的
锡多金属成矿有关,因此桂西北地区石英斑岩集中出露的地方是否具有寻找深部锡多金属矿的前景值得关注。同时,该期
岩浆活动是否与以卡林型金矿为代表的低温热液矿床有成因上的联系尚需更多矿床地质和年代学资料的证实。     

西秦岭金厂石英闪长岩的岩浆混合成因：岩相学和锆石U-Pb年代学证据及其构造意义

位于西秦岭南部的金厂石英闪长岩岩体内含有大量镁铁质暗色微粒包体,包体大多呈浑圆状和水滴状,部分呈不规则拉长状,与寄主岩的接触界线截然或呈渐变过渡关系。石英闪长岩中的磷灰石呈短柱状,而包体中的磷灰石则呈细长针状,反映基性岩浆的快速冷凝结晶。石英闪长岩中的斜长石发育振荡环带,核部的斜长石An低,而边部斜长石An先急剧上升,复又下降;核部与边部之间存在明显的间断,同时斜长石边部包裹有暗色矿物,指示其形成时可能有更基性的岩浆注入。寄主岩中的角闪石大多为普通角闪石和镁普通角闪石,属SiO2饱和型,而包体中角闪石一部分为镁普通角闪石,属SiO2饱和型,一部分为韭闪石、韭闪石质普通角闪石,属SiO2不饱和类型。包体中的角闪石自核部到边部,Al2O3与TiO2含量急剧下降,说明核部和幔部相对于边部形成于更高温的环境。寄主岩中黑云母部分为铁质黑云母,部分为镁质黑云母,而包体中黑云母均为镁质黑云母,在∑FeO/(∑FeO+MgO)对MgO图解上寄主岩与包体中黑云母均落入壳-幔混源区。寄主岩和包体中的锆石均为典型的岩浆锆石,LA-ICP-MS锆石U-Pb定年表明它们的形成年龄分别为212±2Ma及215±1Ma(2σ),在误差范围内基本一致,证明二者同时形成。综合以上岩相学和年代学证据认为,金厂石英闪长岩和镁铁质暗色微粒包体是幔源基性岩浆和壳源酸性岩浆混合作用的产物,形成于秦岭造山带中三叠世造山后伸展环境。结合区域上的研究结果认为,中—晚三叠世时期的幔源岩浆底侵和下地壳部分熔融在西秦岭广泛存在。     

Occurrence and significance of a quartz–amphibole schist xenolith within a mafic microgranular enclave in the Xiangshan volcanic-intrusive complex,SE China

The Xiangshan volcanic-intrusive complex is composed of rhyolitic crystal tuffs, welded tuffs, rhyodacite, porphyroclastic rhyolitic lava, subvolcanic rocks such as granite porphyry, and late quartz monzonitic porphyry and lamprophyre dikes. We report the first occurrence of a quartz–amphibole schist (QAS) xenolith enclosed within a mafic microgranular enclave (MME) in the Xiangshan volcanic-intrusive complex. The mineralogy of this xenolith consists of amphibole, biotite, quartz, and minor plagioclase. Petrographic and mineral composition studies indicate that the protolith of this xenolith likely originated from the metamorphic basement beneath Xiangshan. The amphibole (actinolite and magnesiohorblende) has been partially replaced by orthopyroxene at 800–1000°C and by diopside at <700°C, according to mineral thermometers; this replacement process may have taken place after the xenolith was trapped by the mafic magma host (now an MME). Studies of the QAS xenolith provide new information on the emplacement history of the mafic magma. The peak metamorphic temperature for amphibole replaced by pyroxene is higher than the crystallization temperature of the subvolcanic magma, which indicates that the heat of pyroxene formation must have been provided by the engulfing mafic melt. This magma must have emplaced to crustal level and trapped the QAS as a xenolith and then injected into the felsic magma. We suggested that the hybridization processes for the major elements of the pristine mafic magma may have been contaminated by crustal rocks to form its present composition of MME before mafic magma injection. However, the hybridization process appears not to have been formed via a single-stage process because various types of MMEs are presented in the Mesozoic magmatic rocks of SE China.     

石英砂表面铁胶膜的形成——温度和老化时间的影响

以石英砂为载体,在pH值为7和铁摩尔比R为0.1的条件下合成了石英砂表面针铁矿胶膜,并探讨了不同温度和老化时间对针铁矿胶膜形成的影响,以揭示铁胶膜的形成机理。利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对合成胶膜样品分别进行矿物成分和形态的分析。研究结果表明:当石英砂添加量为10 g、老化时间为25 d时,随着温度由30、50、70增加到90℃,胶膜中针铁矿的XRD峰强度明显增强,SEM图像中针铁矿的结晶程度逐渐增强,晶形逐渐变大;当石英砂添加量为10 g、老化温度为60℃时,随着老化时间的延长,胶膜中针铁矿的XRD峰强度先逐渐增强,矿物晶形也先逐渐增大(前18 d),18 d左右时矿物的晶形较大且较均一,18 d之后XRD峰强度逐渐减弱并趋于稳定,晶形又逐渐变小。     

论石英双晶的复杂性

石英双晶的复杂性远远超出了人们的想象。首先介绍了石英的11种双晶律,然后介绍测试鉴定石英双晶律的各种方法及存在的局限性,综述了近年来石英双晶与温压条件关系、晶格结构匹配理论方面的研究成果,最后结合我们近期用EBSD对岩石中石英双晶的观察、测试结果,指出存在的问题及今后的研究方向。     

LA-ICP-MS Zircon U-Pb Geochronology of Quartz Porphyry from the Niutougou Gold Deposit in Songxian County,Henan Province

The Niutougou gold deposit,located in the center of the Xiong’ershan gold district,western Henan Province,is a large gold deposit with many quartz porphyries found in the area.Based on the field geological investigation of quartz porphyry of Niutougou gold deposit and by using the cathodoluminescence(CL) images analysis and in situ LA-ICP-MS U-Pb isotope dating method of zircons,the inner structure,trace element compositions and U-Pb age of the zircons separated from quartz porphyry were analyzed and determined.Cathodoluminescence(CL) images of zircons show clear magmatic zonations.Trace element analyses of zircons reveal that all zircons show high concentrations of Th,U,and HREE,and the REE patterns of depletion in LREE,with a positive Ce anomaly.Zircon LA-ICP-MS U-Pb dating results show that the quartz porphyry in the Niutougou gold deposit was formed at 159.71±0.99 Ma(about 160 Ma),belonging to the product of magmatic activity in late Middle Jurassic.Combined with the geological characteristics of the Niutougou gold deposit,the formation age of the quartz porphyry and the analysis of the formation age of the granite body exposed in the Niutougou gold deposit,the study suggests that the metallogenic epoch of the Niutougou gold deposit may be Yanshanian in age.     

河北某氧化石英脉型金矿石全泥氰化浸出试验研究

河北省某金矿为氧化石英脉型金矿石,矿石中的金粒微细,平均粒径为0.011 3mm,包裹于黄铁矿、褐铁矿、石英中的金占64.68%,有一部分呈微细粒包裹在土状褐铁矿中,对这种细粒分散的含金氧化矿石采用全泥氰化浸金工艺。将原矿磨矿细度确定为-200目含量占85%,加入石灰对金矿石进行碱预处理,再加入氰化钠浸金,取得了浸出率为96.89%,吸附率为99.55%的试验结果。