青藏高原盐湖硼酸盐形成问题

目前已知世界上硼酸盐沉积的类型有四种:1)与泉华沉积有关.2)与火山活动有关.3)与古盐矿床有关.4)与盐湖有关的。后者实际上也往往与温泉和火山活动有着密切的联系。世界上盐湖中的硼酸盐主要分布在美国西部的加里福尼亚州和内华达州、南美西部安底斯高原的东侧(其中包括智利、秘鲁、阿根廷和玻利维亚等)和我国的青藏高原。我国青藏高原盐湖的硼酸盐无论在资源储量方面或在矿物种类方面都比其它地区丰富得多。     

Hydrochemical Dynamic Characteristics and Evolution of Underground Brine in the Mahai Salt Lake of the Qaidam Basin Qinghai-Tibet Plateau

The mineral rock salts present in the Mahai Salt Lake of the Qaidam basin exhibit high solubilities in water. In addition, the multicomponent underground brine exhibits a high salinity and is easily precipitated. In the natural state, brine transport in the brine layer is extremely slow, and the brine is in a relatively stable chemical equilibrium state with the rock salt media. However, during mining, both the seepage and the chemical fields fluctuate significantly, thereby disrupting the equilibrium and leading to variations in the chemical composition and dynamic characteristics of the brine. Therefore, we selected underground brine from the Mahai Salt Lake, collecting a total of 183 brine samples over three stages of mining (i.e., the early stage of underground brine extraction, the initial stage of mining, and the later stage of mining). Using a range of analytical techniques, the chemical dynamics of the underground brine water and its evolution were systematically studied. We found that evaporation and enrichment were the main mechanisms of underground brine evolution in the Mahai Salt Lake, with cation exchange and mineral dissolution/precipitation being key factors in determining the dynamic characteristics and evolution of the brine.     

Gypsum as a monitor of the paleo-limnological–hydrological conditions in Lake Lisan and the Dead Sea

The isotopic composition and mass balances of sources and sinks of sulfur are used to constrain the limnological–hydrological evolution of the last glacial Lake Lisan (70–14 ka BP) and the Holocene Dead Sea. Lake Lisan deposited large amounts of primary gypsum during discrete episodes of lake level decline. This gypsum, which appears in massive or laminated forms, displays δ³⁴S values in the range of 14–28‰. In addition, Lake Lisan’s deposits (the Lisan Formation) contain thinly laminated and disseminated gypsum as well as native sulfur which display significantly lower δ³⁴S values (−26 to 1‰ and −20 to −10‰, respectively). The calculated bulk isotopic compositions of sulfur in the sources and sinks of Lake Lisan lacustrine system are similar (δ³⁴S ≈ 10‰), indicating that freshwater sulfate was the main source of sulfur to the lake. The large range in δ³⁴S found within the Lisan Formation (−26 to +28‰) is the result of bacterial sulfate reduction (BSR) within the anoxic lower water body (the monimolimnion) and bottom sediments of the lake.

Precipitation of primary gypsum from the Ca-chloride solution of Lake Lisan is limited by sulfate concentration, which could not exceed 3000 mg/l. The Upper Gypsum Unit, deposited before ca. 17–15 ka, is the thickest gypsum unit in the section and displays the highest δ³⁴S values (25–28‰). Yet, our calculations indicate that no more than a third of this Unit could have precipitated directly from the water column. This implies that during the lake level decline that instigated the precipitation of the Upper Gypsum Unit, significant amounts of dissolved sulfate had to reach the lake from external sources. We propose a mechanism that operated during cycles of high-low stands of the lakes that occupied the Dead Sea basin during the late Pleistocene. During high-stand intervals (i.e., Marine Isotopic Stages 2 and 4), lake brine underwent BSR and infiltrated the lake’s margins and adjacent strata. As lake level dropped, these brines, carrying ³⁴S-enriched sulfate, were flushed back to the shrinking lake and replenished the water column with sulfate, thereby promoting massive gypsum precipitation.

The Holocene Dead Sea precipitated relatively small amounts of primary gypsum, mainly in the form of thin laminae. δ³⁴S values of these laminae and disseminated gypsum are relatively constant (15 ± 0.7‰) and are close to present-day lake composition. This reflects the lower supply of freshwater to the lake and the limited BSR activity during the arid Holocene time and possibly during former arid interglacials in the Levant.     

A Brine Evolution Model and Mineralogy of Chemical Sediments in a Volcanic Crater,Lake Kitagata,Uganda

Lake Kitagata, Uganda, is a hypersaline crater lake with Na–SO₄–Cl–HCO₃–CO₃ chemistry, high pH and relatively small amounts of SiO₂. EQL/EVP, a brine evaporation equilibrium model (Risacher and Clement 2001), was used to model the major ion chemistry of the evolving brine and the order and masses of chemically precipitated sediments. Chemical sediments in a 1.6-m-long sediment core from Lake Kitagata occur as primary chemical mud (calcite, magadiite [NaSi₇O₁₃(OH)₃·3H₂O], burkeite [Na₆(CO₃)(SO₄)₂]) and as diagenetic intrasediment growths (mirabilite (Na₂SO₄·10H₂O)). Predicted mineral assemblages formed by evaporative concentration were compared with those observed in salt crusts along the shoreline and in the core from the lake center. Most simulations match closely with observed natural assemblages. The dominant inflow water, groundwater, plays a significant role in driving the chemical evolution of Lake Kitagata water and mineral precipitation sequences. Simulated evaporation of Lake Kitagata waters cannot, however, explain the large masses of magadiite found in cores and the formation of burkeite earlier in the evaporation sequence than predicted. The masses and timing of formation of magadiite and burkeite may be explained by past groundwater inflow with higher alkalinity and SiO₂ concentrations than exist today.     

西藏扎布耶碳酸盐型盐湖卤水相化学研究

中国盐湖资源丰富,且水化学类型齐全。西藏扎布耶盐湖位于西藏高原腹地,该湖卤水水化学类型为碳酸盐型,已处于盐湖演化晚期,是一个固液共存的盐湖矿床,具有很好的工业开发价值。笔者分别在15℃、25℃下对该卤水进行了等温蒸发实验,研究了在此两个温度下卤水中各元素富集行为和盐类矿物析出规律。并通过讨论其与国内外碳酸盐型和硫酸盐型锂盐湖的卤水蒸发路径和矿物析出异同,指出扎布耶盐湖具有其独特的卤水蒸发析盐路径。在本实验中低温有利于卤水中锂的富集,而高温有利于硼的富集,碳酸锂和钾盐交叉析出,低温时钾的矿物主要为钾石盐,高温时主要为钾芒硝,高温有利于获得高品位的碳酸锂混盐。     

Marine-like potash evaporite formation on a continental playa: case study from Chott el Djerid, southern Tunisia

An exceptional flood in January 1990 led to the formation of a large ephemeral lake on the Chott el Djerid, a salt playa in southern Tunisia. Repeated observations made during 1990 show that the ephemeral lake underwent four evolutionary stages: (1) initial flooding, (2) evaporative concentration of lake waters, (3) the movement of concentrated brine pools over the playa surface as a result of wind action, and (4) total desiccation of the lake by September 1990. During all four stages the brine chemistry of the lake was monitored. Water inflow into the Chott el Djerid basin was found to have a consistent Ca-SO₄-Cl-rich and HCO₃-CO₃-poor chemistry, reflecting the recycling of homogeneous assemblages of Cretaceous, Mio—Pliocene and Quaternary evaporites within the catchment. As the ephemeral lake shrank, these waters produced an Na-Mg-K-Cl-SO₄ brine which was similar to modern sea water. Mineral saturation data show that, during the desiccation of the lake, saturation with respect to both gypsum and halite was achieved and that the most concentrated brines were ultimately saturated with respect to potash phases. After the desiccation of the lake the main mineral phases found on the Chott included gypsum and halite. In addition, ephemeral deposits of carnallite (observed as carnallitite,3KMgCl_3·6H₂0 + NaCl) were found. This assemblage is that which would be expected to form if the waters had undergone salt norm evaporation at 1 bar pressure at 25°C (SNORM) in the evaporation model proposed by Jones and Bodine (1987). The nature of both the brine chemistry and evaporite mineralogy provides a new and rare example of marine-like potash-bearing evaporites being formed in a contemporary continental playa.     

Quaternary geochemical evolution of the salars of Uyuni and Coipasa, Central Altiplano, Bolivia

The central trough of the Bolivian Altiplano is occupied by two wide salt crusts: the salar of Uyuni, which is probably the largest salt pan in the world (10,000 km²) and the salar of Coipasa (2,500 km²). Both crusts are essentially made of porous halite filled with an interstitial brine very rich in Li, K, Mg, B (up to 4.7 g/l Li, 4.3 g/l B, 30 g/l K and 75 g/l Mg). Lithium reserves are the highest known in the world, around 9 × 10⁶ tons. Potassium, magnesium and boron reserves in brines are also important (around 194 × 10⁶ tons K, 8 × 10⁶ tons B and 211 × 10⁶ tons Mg).

The crusts are the remnant of saline Lake Tauca (13,000–10,000 yr BP). Its salinity was estimated approximately at 80 g/l. Its paleochemistry was derived in two ways: (1) by dissolving the present amounts of all chemical components in the former lake volume, and (2) by simulating the evaporation of the major inflows to the basin. The resulting chemical compositions are quite different. The dissolution-derived one is 5 to 50 times less concentrated in Li, K, Mg, B than the evaporation-simulated ones. However all compositions present the same Na and Cl contents. This suggests either a removal of bittern salts or an enrichment of the former lake water in Na and Cl.

The most probable interpretation is that Lake Tauca redissolved a salt crust akin to that existing today. Several older lakes have been detected on the Altiplano. Nevertheless, such an explanation only pushes the problem back. It is likely that the anomaly was transferred from one lake to an other. Three hypotheses may be put forward: (1) bittern seepage through bottom sediments, (2) uptake of the missing components by minerals, and (3) leaching of ancient evaporites from the catchment area at the beginning of the lacustrine history of the basin. The excess halite could have been recycled from lake to lake. This latter process seems to be the most effective to explain the large excess of Na and Cl over the bittern solutes — Li, K, Mg and B. The occurrence of almost pure Na/1bCl saline springs flowing out from a gypsum diapir in the northern Altiplano gives substantial support to this hypothesis.     

Jointing of two tunnel shields using artificial underground freezing

Freezing was used in the jointing section of two shields (diameter 3.14 m) which ran across at right angles and at 25-m depth under the crossing of main roads for the construction of a 2.4-m diameter sewer tunnel. The object of freezing was to create a frozen barrier to prevent the inflow of water and fine sand into the area to be excavated.

Thirty-five freeze pipes (length about 7 m) were placed from one shield conically in the direction of the flank of another shield with freeze pipes attached to its inside wall. The cooling unit was placed on unoccupied land at about 60 m distant from the jointing section and the freeze pipes were connected with the cooling unit by supply and return pipelines.

The cooling unit had a cooling capacity of 79,000 kcal/h at an evaporation temperature of −27°C and a condensation temperature of +40°C. Freezing was continued for 180 days and the CaCl₂ brine temperature was −25 to −30°C. These works were accomplished without the sinking of shaft and the use of injection, in complete safety with no traffic restriction on the road surface.     

思茅盆地石盐矿物的原位元素含量特征对成矿模式的启示

思茅盆地江城含盐带勐野井地区在“二层楼”钾盐成矿理论的指导下,逐步在侏罗系钾盐资源调查中取得重要成果,但盆地内其他含盐带研究程度薄弱。本文以整董含盐带的磨黑L2井勐野井组(K₁m)盐岩样品为研究对象,通过显微镜观察、扫描电镜能谱分析、石盐矿物元素含量电子探针微区原位测试方法的建立,精细研究了样品岩相学、石盐矿物学及元素含量特征。同时,测试了江城含盐带勐野井地区MK-1井花开左组(J₂h)石盐样品。对比研究两个井样品中石盐矿物微量元素K和Br含量及10³Br/Cl值(质量分数比)特征,结合研究区地质演化,取得以下认识。L2井K₁m(含)泥砾盐岩中石盐矿物发育两类产状:一类是胶结碎屑颗粒的主体石盐,具塑性流变特征;另一类是析出在碎屑中被盐类或黏土矿物碎屑包裹的石盐,两类包裹体特征指示均属次生成因。电子探针测得L2井K₁m的主体石盐、碎屑包裹和勐野井MK-1井J₂h含钾盐层石盐的K含量分别为≤0.09%、≤0.18%和≤0.13%,Br含量分别为≤60×10^-6、70×10^-6~410×10^-6和70×10^-6~500×10^-6,10³Br/Cl值分别为≤0.10、0.12~0.71和0.12~0.85,主体石盐显著低于后二者,处于陆源或海陆混合源石盐阶段或重结晶石盐阶段,而后二者数值接近,大多处在海源石盐阶段,小部分处在海源母液结晶钾石盐阶段和光卤石阶段。推断磨黑L2井碎屑包裹的石盐属深部古盐体刺穿贯入的证据,可能的成矿模式为深部中侏罗统海相古盐体受盐底辟作用迁移到浅层下白垩统勐野井组后,部分被盆地内侧向迁移来的中侏罗世残留海水、盆地周缘汇入的陆源水以及深部热液的共同溶蚀淋滤和混染改造形成新的卤水,部分以固体古石盐砾保留下来,在早白垩世晚期新母液卤水蒸发成盐过程中被形成的盐类和陆源碎屑矿物包裹,后期在母液结晶的主体石盐胶结下沉积成岩和成矿。以上认识完善了“二层楼”成矿理论在整董含盐带的勘探实践。     

Exchange of Na and K between water vapor and feldspar phases at high temperature and low vapor pressure

In order to determine whether gas (steam) containing a small amount of dissolved alkali chloride is effective in promoting base exchange of Na⁺ and K⁺ among alkali feldspars and coexisting brine or brine plus solid salt, experiments were carried out at 400–700°C and steam densities ranging down to less than 0.05. For bulk compositions rich in potassium, the low pressure results are close to previous high-pressure results in composition of the fluid and coexisting solid phase. However, when the bulk composition is more sodic, alkali feldspars are relatively richer in potassium at low pressure than at high pressure. This behaviour corresponds to enrichment of potassium in the gas phase relative to coexisting brine and precipitation of solid NaCl when the brine plus gas composition becomes moderately sodic.

The gas phase is very effective in promoting base exchange between coexisting alkali feldspars at high temperature and low water pressure. This suggests that those igneous rocks which contain coexisting alkali feldspars out of chemical equilibrium either remained very dry during the high-temperature part of their cooling history or that the pore fluid was a gas containing very little potassium relative to sodium.     

罗布泊盐湖富钾卤水成因再探讨——碎屑层卤水蒸发实验分析

罗布泊盐湖钙芒硝岩孔隙中蕴藏有超大型规模的卤水钾矿,富钾卤水成因一直备受关注。罗北凹地从统一的罗布泊大湖区中分隔出来后,成盐过程中其湖水仍以南部大湖的补给为主,罗北凹地卤水化学演化与"大耳朵"湖水密切相关。"大耳朵"湖区含石膏碎屑层普遍储藏有卤水,应该是罗北凹地盐湖的"源卤水",钾离子(ρ(K~+)为3.12 g/L左右)已初步富集,平均矿化度为198.83 g/L。为了查明该卤水的化学演化趋势及析盐序列,笔者于2009年、2010年两次采集了大量卤水样品,分别进行室内等温蒸发和自然蒸发实验。蒸发实验结果表明:随着卤水浓缩首先析出(硬)石膏,随后析出大量石盐,最后出现少量钾石盐和光卤石,与EQL/EVP卤水蒸发模型模拟结果相似。将碎屑层卤水蒸发过程中化学组成变化与罗北凹地卤水进行对比,结果显示罗布泊古湖水蒸发至石膏沉积之后,在罗北凹地水化学组成明显发生变化,没有大量石盐沉积,而以钙芒硝沉积为主。推测应是受到深部"富钙水"的持续补给,而"大耳朵"湖起到"预备盆地"的作用,罗布泊古湖水经"大耳朵"湖蒸发浓缩后,钾离子得到初步富集,在流入罗北凹地后与深部"富钙"水混合,强烈蒸发浓缩,大量钙芒硝矿物析出,最后形成富钾卤水。     

Brine substitute liquids for soil freezing at very low temperatures

The strength of a frozen soil increases with decreasing temperature. Furthermore, the speed it takes to form a frozen wall increases on lowering the temperature of the freezing liquid.

With the traditional freezing systems using brine it is difficult to work with temperatures below −30°C. To go lower than this limit, it is necessary to substitute the brine by using freezing liquids that maintain good hydraulic and thermal characteristics at much lower temperatures.

Different organic liquids have been tested and good results have been obtained with some aromatic hydrocarbon mixes from the terpene family.

As a result of the research, for practical purposes a by-product ofa distilling citrus fruit skins has been selected. This liquid solidifies at −100°C approx. and maintains a low viscosity rate below −30°C.

The present paper describes the thermal and hydraulic properties of this product as a function of the temperature concerned and compares them to the same properties of classic brines of CaCl₂.     

川东北普光地区深层富钾卤水钾资源提取研究

四川盆地地下卤水资源丰富,尤其川东北地区地下卤水富含高品质钾资源。本项目以四川普光地区富钾卤水为研究对象,根据卤水组成,采用模拟计算并结合实验验证的方法,研究了高温蒸发时,氯化钠、氯化钾、光卤石、硼酸等矿物的析出阶段及特点。研究结果表明,当蒸失水率约80%时,体系中约85%的NaCl析出,同时KCl达到饱和,继续蒸发可获取钾石盐。控制总蒸失水率94%~95%时分离,体系中大于80%的钾可在这一阶段析出,且湿基中KCl品位可高达约45%;析出钾石盐后的卤水降至室温可获得NaCl、KCl、KCl·MgCl₂·6H₂O及H₃BO₃的混合物,硼的析出率可达到约80%。同时,研究表明,将蒸失水率约80%时分离石盐后的卤水直接降温可以获得湿基品位约高达70%的钾石盐矿,钾析出率约50%。综合对比分析,提出两条以钾资源开发为主的工艺路线:其一为“高温蒸发析氯化钠-高温蒸发析氯化钾-冷却析钾硼混盐”,通过加工获得KCl及H₃BO₃产品;其二为“高温蒸发析氯化钠-冷却析钾”,通过加工获得高端KCl产品。     

Mantle fluid evolution—a tale of one diamond

Microinclusions analyzed in a coated diamond from the Diavik mine in Canada comprise peridotitic minerals and fluids. The fluids span a wide compositional range between a carbonatitic melt and brine. The diamond is concentrically zoned. The brine microinclusions reside in an inner growth zone and their endmember composition is K₁₉Na₂₅Ca₅Mg₈Fe₃Ba₂Si₄Cl₃₂ (mol%). The carbonatitic melt is found in an outer layer and its endmember composition is K₁₁Na₂₁Ca₁₁Mg₂₆Fe₇Ba₂Si₁₀Al₃P₂Cl₅. The transition in inclusion chemistry is accompanied by a change in the carbon isotopic composition of the diamond from −8.5‰ in the inner zone to −12.1‰ in the outer zone. We suggest that this transition reflects mixing between already evolved brine and a freshly introduced carbonatitic melt of different isotopic composition.

The compositional range found in diamond ON-DVK-294 is the widest ever recorded in a single diamond. It closes the gap between brine found in cloudy octahedral diamonds from South Africa and carbonatitic melt analyzed in cubic diamonds from Zaire and Botswana. Thus, all microinclusions analyzed to date fall along two arrays connecting the carbonatitic melt composition to either a hydrous-silicic endmember or to a brine endmember. This connection suggests that many diamonds are formed from fluids derived form a mantle source not significantly influenced by local heterogeneities.     

Crystal chemistry of suspended matter in a tropical hydrosystem, Nyong basin (Cameroon, Africa)

Suspended matter (SM) from the Nyong basin (Cameroon, Africa), a tropical watershed, was collected by tangential flow ultrafiltration to separate particulate (>0.45 μm) and colloidal (<0.45 μm; >20 kDa) fractions. In this basin, two distinctive systems in a selected small catchment (Nsimi–Zoétélé) of the Nyong river basin have been considered: (i) colourless water (groundwater and spring) with a low suspended load (<3 mg/l) and a low total organic carbon content (TOC<1 mg/l) and (ii) coloured water (Mengong brook and Nyong river), which is organic rich (TOC>10 mg/l) and contains higher amounts of SM (10–20 mg/l) than the colourless water. Freeze-dried samples of SM have been analysed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR), and visible diffuse reflectance spectroscopy (DRS).

Colourless water mainly contains mineral phases, such as poorly ordered kaolinite, plus quartz and goethite in the particulate fraction, and euhedral kaolinite plus amorphous iron oxyhydroxides in the colloidal fraction. In contrast, the SM in coloured water is mainly organic in nature. The mineral phases in the particulate fraction are similar to those from clear water, but with additional phytoliths and diatom frustules composed of biogenic opal. In the colloidal fraction, complexation of Fe³⁺ and Mn²⁺ with organic matter is evidenced by EPR, together with significant occurrence of Fe oxyhydroxides associated with organic matter.

The sites of Al, Si, Fe, Mn in colloidal fractions derived from spectroscopic analyses are discussed with reference to chemical analyses performed by inductively coupled plasma mass spectrometry. Most of the observed solid phases or species correspond to those expected from published thermodynamic calculations for the same hydrosystem, except the colloidal iron oxyhydroxides in the coloured water. The presence of such iron phases is emphasised since they are expected to have large sorption capacities for numerous trace elements.

The crystal chemistry of SM is used to discuss the origin of the mineral particles transported from the soil to the main rivers in terms of mechanical and chemical erosion processes.     

CO2 production in tar sand reservoirs under in situ steam temperatures: Reactive calcite dissolution

Recovery of highly viscous oil from some of the deeper oil sand deposits of northern Alberta, Canada, is made possible through injection of heat by steam or hot water flooding of the reservoirs. The rise in temperature lowers the viscosity of the bitumen allowing it to be produced. The increase in temperature accelerates the reactions between the matrix and pore minerals of the formation and can produce reaction products which can significantly alter the permeability of the reservoir. If carbonate minerals are present in the reservoir, inorganic CO₂ may also be a reaction product.

The Grand Rapids reservoir consists of relatively clean quartz sand containing 7 wt.% kaolinite, 1 wt.% calcite and a trace of smectite. Core floods of this sand by a neutral NaCl brine at 265°C, 8.2-MPa overburden pressure, 6.0-MPa fluid pressure and a flow velocity of 0.4 pore volumes per hour were used to determine the potential for hydrothermal reactions between clays and carbonate minerals in a natural reservoir sand. Reaction progress was followed by continuous sampling of the production fluids. The produced water was analyzed and the phase chemistry was calculated back to the run conditions using the computer code SOLMNEQF.

Mass-balance considerations on produced total inorganic carbon (TIC) show that calcite broke down very quickly, the maximum in CO₂ production occurring after only one pore volume of fluid had passed through the core. The Ca released from the breakdown of calcite was incorporated in the formation of smectite as was shown by post-run clay mineral analysis by the following unbalanced chemical reaction:

calcite+kaolinite+H₄Si04Ca-smectite+H₂0+CO₂

Silica was supplied by the dissolution of quartz. Silica concentrations analyzed in the production fluid were depressed from those predicted by previously published quartz rate equations because of the rapid rate of smectite synthesis.

These observations were used to formulate the following model for the passage of the first pore volume of NaCl brine through the core. Initially calcite is present throughout the core. As the brine enters the inlet of the core, it equilibrates with calcite. The brine remains in equilibrium with calcite throughout the core as quartz and kaolinite react to form smectite. This model was tested with the computer code PATH.UBC using CO₂ production as a measure of the progress variable ξ. A best fit was achieved to the produced fluid chemistry by varying relative dissolution rates of kaolinite and quatz and varying the suppression of precipitation of certain minerals.     

柴达木盆地大柴旦硼矿床地质特征及成矿机理

大柴旦盐湖因蕴藏固体和液体硼矿资源成为柴达木盆地诸多盐湖中最早被关注和开发的盐湖之一。不仅如此,大柴旦盐湖还沉积有全球少有分布的特色柱硼镁石矿床。此种特色硼矿床的成矿环境和形成机理目前尚未得到应有的关注和研究。本研究基于大柴旦盐湖因开采硼矿而揭露出来的湖中高分辨率的天然沉积剖面DCD-2和DCD03,利用岩性地层学、沉积学、矿物学、地球化学以及AMS 14 C年代学等多指标研究方法,深入探讨了更具特色的湖底柱硼镁石矿层以及其他硼矿层的成矿环境和成矿机理,丰富和完善了盐湖硼矿床成因理论。研究结果显示,大柴旦湖底柱硼镁石矿层(第一硼矿层)形成年代始于BC 1790a左右。湖底柱硼镁石含量为35%,B2O3含量约为3%~16%,属于中低品位硼矿层;而湖滨钠硼解石和水方硼石含量分别为82%和35%,B2O3平均含量约为3%~9%,属于低品位硼矿层。硼矿形成前的较长时期内,大柴旦盐湖是以碎屑沉积为主的非盐湖相沉积环境,此后快速进入硫酸盐型盐湖阶段和湖底柱硼镁石矿层形成阶段。湖底柱硼镁石以及湖滨钠硼解石和水方硼石是在特定水文地球化学条件和湖泊环境下形成,在湖区的不同地带,由于不同的成矿作用和成矿机理形成了不同的硼酸盐矿物或硼矿床。大柴旦盐湖硼酸盐矿床的形成受控于硼自身内在地球化学特性及其外在控制条件,是内外条件耦合的结果。在固体硼酸盐整个形成过程中,盐湖卤水都呈现弱碱性—碱性,这是盐湖硼酸盐沉积形成的先决条件。文章提出了盐湖固体硼酸盐的具体形成机理并确定大柴旦盐湖硼矿床为高山-深盆-浅水成矿模式。     

Partitioning of boron among melt, brine and vapor in the system haplogranite–H2O–NaCl at 800 °C and 100 MPa

Fluid-saturated experiments were conducted to investigate the partitioning of boron among haplogranitic melt, aqueous vapor and brine at 800 °C and 100 MPa. Experiments were carried out in cold-seal pressure vessels for 1 to 21 days, and utilized powdered synthetic subaluminous haplogranite glass doped with 1000 ppm B (crystalline H₃BO₃) and variable amounts of NaCl and H₂O at a fluid/haplogranite mass RATIO=1:1. Run-product glasses were analyzed for boron concentration by secondary ion mass spectrometry (SIMS) and for major elements and chlorine by electron microprobe. The composition of the coexisting fluid was calculated by mass balance. Boron partition coefficients between aqueous vapor and hydrous granitic melt range from 3.1 to 6.3, and demonstrate a clear preference of boron for the vapor over the hydrous melt. Partition coefficients between brine and hydrous granitic melt vary from 0.45 to 1.1, suggesting that boron has no preference for the brine or the melt. The bulk fluid–melt partition coefficients for low-salinity and high-salinity experiments are D_B^(vapor/melt)=4.6±1.3 and D_B^(brine/melt)=0.91±0.49, respectively. The corresponding vapor–brine partition coefficient is 5.0±3.1, demonstrating that boron partitions preferentially into the vapor over the brine at the conditions of this study. The preferential incorporation of boron in the aqueous vapor is controlled by borate speciation and solution mechanism. The dominant borate species in aqueous fluids, H₃BO₃^o, is highly soluble in aqueous vapor (X_B2O3=0.187); however, B₂O₃ is immiscible in NaCl liquid. Consequently, concentrations of boron in aqueous vapor are significantly higher than in the coexisting brine. Furthermore, Na–B complexing in the melt at high chlorine fluid contents stabilizes boron in the melt thereby contributing to the non-preferential partitioning of boron between brine and melt. The commonly observed association of tourmalinization (boron metasomatism), brecciation and ore deposition in nature is consistent with the preferential partitioning of boron into aqueous vapor of magmatic-hydrothermal systems predicted by this study.     

The duisburg method of metro-construction, a successful application of the gap freezing method

Between March 1977 and August 1979 contract No.4 of the Stadtbahnbau (Metro-construction) in Duisburg was executed, making successful use of gap freezing.

The gap freezing was necessary because the Metro-tunnel is crossed by a groundwater stream (flow velocity up to 15 m/d) and it had to be assured that open cut construction of the tunnel was possible and that the original situation could be reinstated as far as possible after completion.

The Duisburg building ground also made a special construction method necessary. Ground strata: from surface to 2–4 m, civilisation deposits; from ˜ 4 m to ≈ 25–28 m below surface, glacial sand and gravel deposits, containing stones with a diameter > 20 cm and even boulders of 1 m³ and more; from approximately 28 m below surface, layers of Tertiary clay and silt; the groundwater table is ˜ 8 m below the surface, the stream flowing within the sand and gravel deposits from SE to NW (towards the Rhine).

Installing a groundwater barrier, for instance by erecting a continuous diaphragm wall enclosure, was already ruled out in early design stages as was the use of driven steelpiles.

At the inception of the design in 1974, it was decided first to carry out a measuring scheme to establish the groundwater flow velocity. This was followed by a large scale (1:1) trial freezing to ascertain the feasibility of the gap-freezing method.

When these experiments were scientifically valued it was established, that the risk involved was acceptable. The contract documents were prepared prescribing a combination of “cover and cut” with gap-freezing, which is tentatively called the “Duisburg method of Metro-construction”.

During the construction a large scale measuring and scientific research programme was carried out.     

新疆罗布泊盐湖氢氧锶硫同位素地球化学及钾矿成矿物质来源

罗布泊罗北凹地第四系上部盐层中蕴藏丰富的卤水,卤水中则富含钾（ＫＣｌ平均品位为１．４０％）。文章通过对罗布泊卤水氢、氧、锶及硫同位素等分析及与塔里木盆地（河流）、柴达木盆地等地区对比研究,确定了罗布泊富钾卤水源于地表水,可能主要是塔里木盆地南北缘河流水;卤水中的硫钾等物质组分主要来源于南天山、塔里木盆地西北、西南部中新生代石膏钙芒硝石盐矿床或地层及其古代地层卤水。由于第四纪期间塔里木盆地西部抬升。