Sulfur,chlorine, and fluorine degassing and atmospheric loading by the 1783–1784 AD Laki (Skaftár Fires) eruption in Iceland

 The 1783–1784 Laki tholeiitic basalt fissure eruption in Iceland was one of the greatest atmospheric pollution events of the past 250 years, with widespread effects in the northern hemisphere. The degassing history and volatile budget of this event are determined by measurements of pre-eruption and residual contents of sulfur, chlorine, and fluorine in the products of all phases of the eruption. In fissure eruptions such as Laki, degassing occurs in two stages: by explosive activity or lava fountaining at the vents, and from the lava as it flows away from the vents. Using the measured sulfur concentrations in glass inclusions in phenocrysts and in groundmass glasses of quenched eruption products, we calculate that the total accumulative atmospheric mass loading of sulfur dioxide was 122 Mt over a period of 8 months. This volatile release is sufficient to have generated ∼250 Mt of H₂SO₄ aerosols, an amount which agrees with an independent estimate of the Laki aerosol yield based on atmospheric turbidity measurements. Most of this volatile mass (∼60 wt.%) was released during the first 1.5 months of activity. The measured chlorine and fluorine concentrations in the samples indicate that the atmospheric loading of hydrochloric acid and hydrofluoric acid was ∼7.0 and 15.0 Mt, respectively. Furthermore, ∼75% of the volatile mass dissolved by the Laki magma was released at the vents and carried by eruption columns to altitudes between 6 and 13 km. The high degree of degassing at the vents is attributed to development of a separated two-phase flow in the upper magma conduit, and implies that high-discharge basaltic eruptions such as Laki are able to loft huge quantities of gas to altitudes where the resulting aerosols can reside for months or even 1–2 years. The atmospheric volatile contribution due to subsequent degassing of the Laki lava flow is only 18 wt.% of the total dissolved in the magma, and these emissions were confined to the lowest regions of the troposphere and therefore important only over Iceland. This study indicates that determination of the amount of sulfur degassed from the Laki magma batch by measurements of sulfur in the volcanic products (the petrologic method) yields a result which is sufficient to account for the mass of aerosols estimated by other methods. Received: 30 May 1995 / Accepted: 19 April 1996     

An ash fall within the Loch Lomond stadial

Cores recovered from the Witch Ground Basin (central North Sea) and the northern Rockall Trough, near the Wyville-Thomson Ridge have been found to contain volcanic glass shards. These have been correlated with the Vedde Ash Bed of western Norway, which has an age of 10600± 60yr BP, and with North Atlantic ash zone 1. This is the first time that this important chronostratigraphic marker has been identified on the UK continental shelf and it is suggested that it might also be present in northern Scotland. If so, it would be a useful tool in the correlation of terrestrial, lacustrine and marine sequences of the Loch Lomond Stadial.     

不同成因类型石英与石英玻璃气泡缺陷间关系探讨

对不同成因类型石英的气液包体含量与石英玻璃气泡缺陷间的关系进行了对比研究，总结了一些规律，对石英玻璃工业原料的地质找矿具有一定的指导意义。     

The Morphological and Optical Properties of Volcanic Glass: A Tool to Assess Density-induced Vertical Migration of Tephra in Sediment Cores

Volcanic ash layers in sediment cores are valuable geochronological markers in paleolimnological research. The composition of volcanic glass is related to identifiable, chronologically distinctive volcanic eruptions. Consequently, tephra layers provide time horizons allowing regional-scale correlations for lake sediments. Volcanic glass is often present in samples routinely prepared by paleolimnologists such as diatom slides and thin sections. Knowledge of the morphological and optical properties of volcanic glass allows for its identification. This is essential for the identification of ash layers that are not macroscopically visible or to track their vertical migration in soft organic sediments. The purposes of this note are to: (1) describe how the morphological (i.e., shape, vesicularity) and optical (i.e., refractive index and birefringence) properties can be used to identify volcanic glass in preparations from lake sediments; and (2) show how the quantification of volcanic glass from diatom slides is used to quantify the density-induced displacement of a 4.5 cm-thick Mazama ash-layer through organic sediments and to approximate its timing of initial deposition.     

Tephra glass chemistry provides storage and discharge details of five magma reservoirs which fed the 75 ka Youngest Toba Tuff eruption,northern Sumatra

The Youngest Toba Tuff contains five distinct glass populations, identified from Ba, Sr and Y compositions, termed PI (lowest Ba) – PV (highest Ba), representing five compositionally distinct pre-eruptive magma batches that fed the eruption. The PI–PV compositions display systematic changes, with higher FeO, CaO, MgO, TiO₂ and lower incompatible element concentrations in the low-SiO₂ PIV/PV, than the high-SiO₂ PI–PIII compositions. Glass shard abundances indicate PIV and PV were the least voluminous magma batches, and PI and PIII the most voluminous. Pressure estimates using rhyolite-MELTS indicate PV magma equilibrated at ~6 km, and PI magma at ~3.8 km. Glass population proportions in distal tephra and proximal (caldera-wall) material describe an eruption which commenced by emptying the deepest PIV and PV reservoirs, this being preferentially deposited in a narrow band across southern India (possibly due to jet-stream and/or plinian eruption transport), and as abundant pumice clasts in the lowermost proximal ignimbrites. Later, shallower magma reservoirs erupted, with PI being the most abundant as the eruption ended, sourcing the majority of distal ash from co-ignimbrite clouds (PI- and PIII-dominant), where associated ignimbrites isolated earlier (PIV- and PV-rich) deposits. This study shows how analysis of tephra glass compositional data can yield pre-eruption magma volume estimates, and enable aspects of magma storage conditions and eruption dynamics to be described.     

安阳市霞石正长岩开发利用方向与前景

霞石正长岩是安阳市的优势特色矿产，是发展新型节能节碱玻璃、陶瓷的原料，高起点、高投入地作好霞石正长岩的开发利用，是适应当前经济社会发展要求的正确选择，也是发展包括安阳在内的河南省玻璃和陶瓷工业的重要途径，其开发利用前景广阔。建议安阳市霞石正长岩生产规模设计为20万吨精矿／年。     

龙凤山气田易漏失井固井工艺技术研究与应用

龙凤山气田属于典型的裂缝性储层,钻井过程中漏失问题突出。该气田地层压力系数低、气层活跃、井壁稳定性差,固井难度较大。针对本区块特点,强化固井工艺措施,做好钻完井过程的防漏、承压堵漏工作,优选完井方法,采用变排量顶替工艺技术,开展低密度水泥浆体系优选研究,合理设计浆柱结构,有效地解决了固井过程中的漏失和候凝期间气窜等问题,保证了固井质量,实现了油层的有效封固,现场应用效果良好。     

高温熔融研制安山岩玻璃标准物质初探

地质标准玻璃物质在激光剥蚀等离子体质谱技术应用中发挥着重要的作用,目前国内对于地质标准玻璃物质合成方法研究还较少,一定程度上限制了该技术的高精度应用。本文对国家一级安山岩粉末标准物质(GSR-2)采用高温熔融法合成安山岩玻璃标准物质(GSR-2G),探讨了熔融温度、时间、淬火方式对安山岩玻璃均一性的影响。实验确定了在熔融温度1300℃、熔融时间4 h的最佳条件下,采用液氮淬火合成的安山岩玻璃标准物质GSR-2G均一性较好,可作为微区分析的内部标准物质。利用193 nm ArF准分子激光剥蚀-四极杆等离子体质谱(LA-Q-ICPMS)分析合成的GSR-2G中35个微量元素和10个主量元素,精密度(RSD)均优于10%。GSR-2G的7Li～238U共35个微量元素,化学法分析测定值与LA-Q-ICPMS测定值的相对偏差优于10%;23Na～56Fe共10个主量元素,电子探针分析测定值与LA-Q-ICPMS测定值一致。利用LA-Q-ICPMS法分析GSR-2G中40个元素,获得的平均测定值可作为初步参考值。     

X射线荧光光谱法测定锰矿石中主次成分

采用玻璃熔片法制样,建立测定锰矿石中TMn、TFe、SiO2、Al2O3、CaO、MgO、K2O、TiO2、P2O5等主次成分的X射线荧光光谱分析方法。确定了仪器最佳参数,采用系列标样建立了校准曲线。对稀释比、熔样时间等进行了探讨,结果表明,试样和熔剂的质量比以1﹕30、熔样时间以10min为好,所得试样在熔剂中的分散度(浓度)适当,可同时适合试样中高、低含量组分的测定。采用熔融法分解试样的方法有效地消除了试样的粒度效应,精确度几准确度试验表明,荧光玻璃熔片法能满足锰矿石中各元素的分析要求。