原地宇宙成因核素测年中石英样品分离提纯的几组实验对比

原地宇宙成因核素测年方法在地质及地理研究领域应用广泛,测年对象众多。石英因其致密的晶体结构不易被大气成因10Be污染,以及较低的27Al含量的特点而成为宇宙成因核素测年方法中一种理想的测年物质。在分离石英样品10Be和26Al的实验流程中,石英的提纯是其中的一个关键环节。原始的HCl/H2O2和HF/HNO3蚀刻分离提纯石英方法应用广泛、安全可靠,但处理样品周期长、效率较低。因此,在原始流程的基础上,设计了3组实验流程与原始流程进行对比。结果显示,在样品石英纯度较高的基础上,可以通过减少超声波使用时间、增加蚀刻溶液浓度及每步样品处理量的方法,提高样品的处理效率,同时可以用加热磁力搅拌器替代超声波清洗器进行石英样品的HF/HNO3蚀刻提纯     

张掖盆地龙首山山前高氟地下水的形成

氟是人体的必须元素之一,饮水中氟元素过量会导致地氟病。高氟地下水的形成机制一直是水文地球化学研究的一个热门话题。利用在张掖盆地开展1∶5万水文地质调查所获得的大量水位、水质资料,运用水化学和氘氧同位素方法,在较高精度水平上探讨了龙首山前高氟地下水的形成机制。研究结果表明,龙首山前地下水中的F-主要来源于龙首山含氟岩石,通过季节性洪水的方式补给到盆地的第四系含水层中,并与盆地上游来源的低氟地下水发生混合,使龙首山前地下水分为三个条带。     

From intrusion-related to orogenic mineralization: The Wasamac deposit,Abitibi Greenstone Belt,Canada

The Wasamac deposit is an example of Archean greenstone-hosted gold deposit located in the Abitibi Belt, 15 km southwest of Rouyn-Noranda. The deposit is hosted by a second-order ductile shear zone of the Cadillac–Larder Lake Fault Zone (CLLFZ), known as the Francoeur-Wasa Shear Zone (FWSZ). It regionally sits at the boundary between the orogenic gold district of Noranda and the Kirkland Lake gold district dominated by intrusion-related gold systems. This specific location in-between two different gold mineralization environments sets the Wasamac deposit apart as a prime candidate for investigating hydrothermal processes along the CLLFZ. Within the Wasamac deposit, gold distribution is constrained to the altered mylonitized portion of the FWSZ; lode systems are absent. Hydrothermal alteration and associated disseminated mineralization occurs as a replacement of the Blake River Group metavolcanic units. The hydrothermal signature displays two distinct alkaline alteration assemblages: potassic and albitic, each associated with specific gold characteristics. (1) Potassic alteration is characterized by the crystallization of microcline, carbonates and quartz. Within this assemblage gold is associated with porous pyrite enriched in Te-Ag-Au-Mo-Pb-Bi-W, deposited under oxidizing conditions. Such characteristics are widely described in the Kirkland Lake area, and are found in examples of syenite-related mineralization, such as the Beattie and Malartic gold deposits. (2) The albitic alteration assemblage, composed of albite, sericite and carbonates, reflects more reduced hydrothermal conditions with mineralization characterized by free native gold. This hydrothermal event is coeval with the brecciation of early gold-rich pyrite reflecting a structural overprint that controlled late-stage gold characteristics. These alteration and structural features are common in orogenic gold deposits both worldwide and regionally, particularly at the neighbouring Kerr-Addison and Francoeur deposits, and in lode-gold systems such as in the Sigma-Lamaque deposit.The gold mineralization at Wasamac has similar characteristics to both intrusion-related gold systems and structurally controlled orogenic gold deposits. Hydrothermal and structural crosscutting relationships at Wasamac indicate that a structurally controlled hydrothermal event overprinted earlier potassic magmatic-hydrothermal alteration. This observation supports a multistage process of gold concentration during which new gold characteristics, metal anomalies, fluid conditions and alteration assemblages replaced earlier stages of gold enrichment, in places completely obliterating previous signatures. We propose that the Wasamac deposit was originally related to an alkaline intrusion buried at depth beneath the Francoeur-Wasa Shear Zone.     

地幔橄榄岩捕掳体中尖晶石筛状边的成因

山东的无棣大山和栖霞方山是两个以霞石岩为主的新生代火山,含有大量的地幔橄榄岩捕掳体,橄榄岩捕掳体中的尖晶石常见黑色反应边。在BSE图像上,这些反应边根据结构的不同又可以进一步分为两种:筛状边和均一边。有时两种反应边在同一颗尖晶石中共存并相互过渡。尖晶石捕掳晶和捕掳体中与寄主岩直接接触的尖晶石常发育均一边;发育筛状边的尖晶石则一般不直接与寄主岩接触,但位于捕掳体的边缘。尖晶石的筛状边呈多孔状,为富Cr尖晶石或铬铁矿。筛状边成分上与核部(Cr_2O_3=7.52%~36.75%,Cr#=7.80~44.20,Mg#=44.70~74.48)区别明显,具有高的Cr_2O_3含量(23.42%~65.96%)、Cr#值(78.97~92.49)以及低的Mg#值(17.22~43.02)。另外,筛状边相对其核部(TiO 2=0.00%~0.53%,MnO=0.04%~0.35%)还显示偏高的TiO 2(0.20%~3.60%)和MnO(0.29%~1.93%)。在筛状边附近存在富Al_2O_3(8.00%~17.57%)和MgO(17.89%~26.02%)的玻璃。尖晶石的均一边无孔洞但多发育裂理,成分上与核部突变,并以富TiO 2(20.90%~6.64%)和FeO T(70.79%~53.92%)为特征,最外部为钛磁铁矿。均一边具有明显的成分分带,表现为由内至外TiO 2、FeO T含量逐渐增高,Al_2O_3(0.04%~16.34%)、Cr_2O_3(0.77%~25.69%)和MgO(0.50%~7.16%)含量逐渐降低。尖晶石的两种反应边与寄主岩密切的空间关系说明其成因与寄主岩浆有关。虽然尖晶石筛状边的Cr#值(79.0~92.5)明显高于核部(7.8~44.2),但是其相对核部偏高的TiO 2和MnO含量,以及显著降低的Mg#值均与单纯的部分熔融趋势不吻合。根据尖晶石两种反应边的结构特征、成分特征和相互的空间关系,我们认为筛状边与均一边是岩浆与尖晶石反应不同阶段的产物。当橄榄岩捕掳体被岩浆捕获后,由于成分上的不均衡两者之间将发生溶解反应。反应过程中,尖晶石中不同元素向熔体迁移的速率区别明显,其中Cr是最难熔的元素也是迁移最慢的元素。在反应的初始阶段,由于易溶组份Al、Mg等元素随熔体迁出,尖晶石发育筛状边,并同时伴随Cr#值的显著升高和Mg#值的显著降低。此时,寄主岩浆中的Ti、Mn等元素也部分扩散进入筛状边中的残留尖晶石。如果熔体足够多,反应得以持续进行,筛状边中的Cr最终也将被熔体带走。在反应产生的混合熔体中金属氧化物最早达到饱和并结晶。随着反应的持续进行,结晶出的矿物将继续生长、变粗,并相互连接,直至孔洞消失形成均一边。同时伴随着矿物的不断结晶,溶解界面上的熔体成分也不断变化,从而使均一边具有明显的成分分带。在橄榄岩捕掳体内部,由于渗进捕掳体中的岩浆有限,渗透岩浆与尖晶石之间的反应多限于早期阶段,反应产物为筛状边。在捕掳体边缘,与寄主岩浆直接接触的尖晶石由于参与反应的岩浆量足够多,因此一般产生反应的终端产物———均一边。     

德兴铜矿堆浸场矿石矿物学、Cu伴生元素地球化学特征及意义

德兴铜矿是我国乃至世界著名的低品位多金属岩型铜矿之一。多年来,德兴铜矿在低品位矿石堆浸过程中只对Cu元素进行回收,而对Re、Co、Au、Ag等伴生元素研究甚少。本文采用X射线衍射、扫描电镜与电镜能谱、电子探针以及ICP-MS等方法对德兴铜矿杨桃坞与祝家村堆浸场低品位矿石进行测试分析,研究了低品位矿石矿物组成变化、重要共伴生元素的赋存状态与空间分布规律,并对其进行了综合利用的可行性评价。研究结果表明,Au主要以自然金形式存在,Ag以单质和化合物两种形式存在,Co主要以类质同像形式存在;Re与Mo含量很低,无利用价值;Co元素含量相对较高,均值19 g/t左右,浸出率为73%,因此回收酸性水库中的Co元素可能具有重大经济价值;杨桃坞堆浸场Au平均含量0.10 g/t,几乎无浸出;Ag平均含量0.39 g/t,浸出率较低,可作为一种潜在资源。此外,堆浸场中金红石含量较丰富,平均粒度20μm左右,估算储量达460万吨,有必要对其回收性开展深入研究。     

泥旦沟金矿堆浸试验研究

泥旦沟金矿采用堆浸工艺,对低品位矿石进行提金试验。试验矿石品位2.25g/t,规模4795t。金的浸出率67.74％,单位矿石利润66.8元/t,经济临界品位降至1.23g/t,矿山服务年限得到有效延长。     

Calculation of <Superscript>17</Superscript>O NMR shieldings in molecular models for crystalline MO,M=Mg,Ca, Sr,and in models for alkaline earth silicates

¹⁷O NMR shieldings are calculated for the central O in the molecular model OM₆(OH)₁₂ ^–2, for crystalline alkaline earth oxides, MO, where M=Mg, Ca, and Sr, using both Hartree–Fock and hybrid Hartree–Fock density-functional theory. Agreement of calculated and experimental NMR shifts of CaO and SrO compared to MgO is good, but only if the basis set on the M atoms has sufficient tight d polarization functions. Preliminary results are also presented for nonbridging O in the silicate Si(OH)₃O^– anion, perturbed by alkaline earth cations, giving trends which agree qualitatively with experiment.     

GEOGRAPHICAL ENVIRONMENTAL CHARACTERISTICS OF ENDEMIC FLUOROSIS IN CHINA

Endemic fluorosis is given rise to by human intake of excess fluorine from environment by way of food chain. In China it is one of the extensively prevalent endemic diseases and its distribution shows clearly regional characteristics. In macroscopic sight, three large fluorosis zones may be divided: (1) The arid and semi-arid plains in the north of China. These regions have a dry climate, making fluorine accumulation in the Quaternary deposits. Thus, the drinking water with high content of fluorine is the main cause of the disease formation. (2) The Yunnan-Guizhou Plateau. In the region, rocks and soils rich in fluorine bring about fluorine excess in crop food. This plays an important role in the disease formation. (3) Southeast hills. The hot spring with high content of fluorine leads to fluorosis.The fluorine absorbed by people from the environment is firstly from the drinking water and secondly from the crop food originating from soil. The fluorine in the air can be accumulated in crop leaves to make     

Petrogenetic processes in the ultramafic, alkaline and carbonatitic magmatism in the Kola Alkaline Province: A review

Igneous rocks of the Devonian Kola Alkaline Carbonatite Province (KACP) in NW Russia and eastern Finland can be classified into four groups: (a) primitive mantle-derived silica-undersaturated silicate magmas; (b) evolved alkaline and nepheline syenites; (c) cumulate rocks; (d) carbonatites and phoscorites, some of which may also be cumulates. There is no obvious age difference between these various groups, so all of the magma-types were formed at the same time in a relatively restricted area and must therefore be petrogenetically related. Both sodic and potassic varieties of primitive silicate magmas are present. On major element variation diagrams, the cumulate rocks plot as simple mixtures of their constituent minerals (olivine, clinopyroxene, calcite, etc). There are complete compositional trends between carbonatites, phoscorites and silicate cumulates, which suggests that many carbonatites and phoscorites are also cumulates. CaO / Al₂O₃ ratios for ultramafic and mafic silicate rocks in dykes and pipes range up to 5, indicating a very small degree of melting of a carbonated mantle at depth. Damkjernites appear to be transitional to carbonatites. Trace element modelling indicates that all the mafic silicate magmas are related to small degrees of melting of a metasomatised garnet peridotite source. Similarities of the REE patterns and initial Sr and Nd isotope compositions for ultramafic alkaline silicate rocks and carbonatites indicate that there is a strong relationship between the two magma-types. There is also a strong petrogenetic link between carbonatites, kimberlites and alkaline ultramafic lamprophyres. Fractional crystallisation of olivine, diopside, melilite and nepheline gave rise to the evolved nepheline syenites, and formed the ultramafic cumulates. All magmas in the KACP appear to have originated in a single event, possibly triggered by the arrival of hot material (mantle plume?) beneath the Archaean/Proterozoic lithosphere of the northern Baltic Shield that had been recently metasomatised. Melting of the carbonated garnet peridotite mantle formed a spectrum of magmas including carbonatite, damkjernite, melilitite, melanephelinite and ultramafic lamprophyre. Pockets of phlogopite metasomatised lithospheric mantle also melted to form potassic magmas including kimberlite. Depth of melting, degree of melting and presence of metasomatic phases are probably the major factors controlling the precise composition of the primary melts formed.