Silica mobility and fluid movement during metamorphism of the Connemara schists, Ireland

Quartz veins are developed in a wide range of metasediment types in the upper amphibolite facies rocks of Connemara, and attest to considerable migration of silica. Contrary to common assumptions, there is clear evidence that these veins do not primarily result from movement of fluid to regions of lower P–T down the regional geothermal gradient. Under amphibolite facies conditions, a dilute chloride fluid moving down temperature has the potential to alter 60g of plagioclase to muscovite for each gram of vein quartz precipitated, while cooling over the temperature interval from 650 to 500° C. The absence of significant metasomatic effects in the vein walls effectively precludes a simple origin from such through-flowing, externally derived fluids. The oxygen isotopic composition of matrix quartz shows considerable differences between different rock types (quartzite, pelite and marble), with a range of δ¹⁸O_SMOW from c.+ 11.5% (quartzite) to + 18.5% (marble). In each rock type, vein quartz compositions closely match those of the matrix quartz. These results demonstrate the importance of local segregation processes in the formation of veins, and suggest that fluid convection cells were not developed during metamorphism on a scale larger than the individual sedimentary formations, if at all. Both oxygen isotope data and the absence of metasomatism indicate that veins form primarily by segregation of quartz from the host lithologies, with only a relatively minor component of through flow of externally derived fluid. Veins are clearly not the major pathways of metamorphic dewatering. It is proposed that abundant veins in the predominantly pelitic Ballynakill Formation formed during peak metamorphic D3 folding because the formation was embrittled by high fluid pressures but was capped by impermeable marble. Hence the pelitic formation fractured repeatedly and the pore fluid drained through the fractures to form veins, while irreversible loss through the rest of the succession was a much less important process. In the central mountains of Connemara, rather pure, unreactive quartzites are cut by widely spaced, laterally extensive quartz veins that are axial planar to D3 folds. These veins may mark pathways whereby metamorphic fluid made its way through the massive impermeable quartzite from lower parts of the nappe pile, but here too, oxygen isotope data indicate considerable segregation of locally derived quartz, reflecting the importance of pumping of fluid between wail rocks and fractures relative to the component of through flow.     

湘黔地区震旦纪菌藻硅质岩特征及形成机理探讨

湘黔地区震旦纪菌藻硅质岩化学成分纯净,硅质矿物含量95%以上,几乎都为泥晶—微晶石英,石英结晶度平均为6.35。岩石具菌藻生物结构,以纹层状构造为主。其中丰富的菌藻生物化石,按形态可划分为三种类型。岩石属原生沉积成因,二氧化硅的聚沉一方面通过菌藻有机体的硅化作用,另一方面是菌藻生物化学作用引起微环境变化而导致二氧化硅的聚沉。     

湘西南石英脉型金矿矿物流体包裹体pH值和Eh值的估算

以湘西南石英脉型金矿床为例,研究ｐ Ｈ、Ｅｈ 估算值的结果表明利用围岩蚀变反应方程以及采用碱金属离子、卤素元素离子估算ｐＨ 值是不完善的。本文根据热力学原则（ 相平衡、电价中和） 提出了矿物流体包裹体成分体系计算ｐＨ 估算值的方法,并且讨论了测试包裹体时气体成分外逸是影响ｐＨ 和Ｅｈ 估算值的主要因素之一。     

Oxygen isotope compositions of quartz grains (4–16 μm) from Chinese eolian deposits and their implications for provenance

Oxygen isotope compositions were measured in quartz grains extracted from a 7.0 Ma red clay-loess sequence at Lingtai and six late Pleistocene loess sediments (Malan loess). Results show that the changes in oxygen isotope compositions of Malan loess are basically controlled by the geochemical characteristics of the source materials, while the effect of weathering process after dust deposition could be minor. The oxygen isotope distribution of quartz grains from red clay at Lingtai is similar to that of the overlying loess-paleosol sequence, thus indicating that the red clay at Lingtai has the same eolian origin as the loess-paleosol deposits. Furthermore, the oscillations of the isotope compositions in 4–16 μm-sized quartz grains may reflect the changes, to some extent, of the climatic systems of the source region.     

吐哈盆地南缘彩霞山东石英闪长岩岩株锆石SHRIMP U-Pb测年

彩霞山东石英闪长岩岩株的锆石SHRIMP U-Pb年龄为267.8Ma±1.6Ma,结合克孜尔塔格岩体的同位素年龄综合分析,此年龄值介于王瑜等所研究剪切作用控制的克孜尔塔格岩体右行剪切年龄276～254Ma之间,表明该石英闪长岩岩株的侵位年龄比克孜尔塔格复式岩体晚,为中二叠世早期.     

高纯球形-准球形亚微米晶质SiO2材料的制备与表征

以天然粉石英为基本原料,通过氢氟酸与盐酸混合酸溶蚀技术和机械强力搅拌处理,制备了高纯球形-准球形亚微米晶质SiO2材料。XRD,SEM表征结果表明,制备的高纯球形亚微米晶质SiO2材料为纯结晶SiO2相,粒子呈球形-准球形,球化-准球化率达80%～90%,粒径一般为300 nm～800 nm;其化学组成为:w(SiO2)99.90%,w(Al2O3)192×10-6,w(Fe2O3)33×10-6,w(Mg)1×10-6,w(Ca)2×10-6,w(Cl-)20×10-6。     

Chronology of an oyster reef on the coast of Bohai Bay, China: Constraints from optical dating using different luminescence signals from fine quartz and polymineral fine grains of coastal sediments

Fossil oyster reefs are indicators of past sea levels, and their formation is usually dated by means of radiocarbon. However, radiocarbon dating of the shells from coastal areas may be complicated by the varying sources of carbon. Here we applied optical dating methods to date the samples from above and below a fossil oyster bed in a section on the coast of Bohai Bay, China. The optical ages of the sediments were used to constrain the oyster bed. Single-aliquot regenerative-dose procedures using the OSL signal from fine grain quartz, the IRSL and post-IR OSL signals from polymineral fine grains were employed to determine equivalent dose (D_e). The behaviors of the different luminescence signals from quartz and polymineral grains during D_e measurements were examined. The results showed that the quartz OSL signal is more reliable than the polymineral IRSL and post-IR OSL signals with respect to dating for these coastal samples. The optical ages indicated that the oyster reef formed between ca. 6.2 and 5.0 ka.     

内蒙古大青山北石兰哈达石英闪长岩构造环境讨论

内蒙古大青山北石兰哈达地区的晚古生代黑云石英闪长岩,1∶20万区域地质调查时将其置于华力西中期第二次侵入体(δο42(2)),现经岩石学、地球化学、同位素年代学研究,认为该石英闪长岩为早二叠世岩浆活动的产物。岩石具高铝、高钾、高钙的特点,A/CNK<1.1,σ在2.05～2.83之间,为高钾钙碱性岩,属I型花岗岩类,产于碰撞后的抬升构造环境。岩石稀土总量偏低,LREE富集,δEu=0.8～1.0,稀土曲线呈右倾平滑型,其物质来源很可能是源于软流圈的玄武质岩浆与元古宙地壳物质混合作用的结果。     

JMD型滤池双层滤料的净水试验及比较

大量的试验数据表明石英砂和陶粒组成的双层滤料，其净水处理性能明显好于石英砂和无烟煤双层滤料以及单层石英砂滤料，特别是出水浊度、微絮凝作用，反冲洗周期、藻类的去除、絮凝剂的使用量等指标上具有明显优势，陶粒做为一种新的水处理滤料，正被应用于净水和污水处理。     

粉石英在蓄电池胶壳中的应用

本文着重介绍了粉石英的工艺矿物特性以及其在蓄电池胶壳中的应用效果,证明了粉石英用作蓄电池胶壳的填料,能够改善混炼工艺、提高产品质量、增加填充量、降低生产成本,是一种理想的橡胶填料。