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对2002年3月20日中国黑龙江省哈尔滨市遭遇的特大沙尘天气沙尘沉降物进行的粒度分析表明，沙尘沉降物属粉质亚砂土，以4～63μm的粉砂为主，占71．18％，〉63μm的砂粒组分占21．7％，〈4μm的粘土组分含量最少，仅占7．13％。粒度为二峰态分布，292～34．7μm粒级的粗粉砂形成第一主峰，含量约占7．4％，420．5-500μm粒级的中砂组分形成第二主峰，含量约占1.29％，而0.69-0．82μm粒级的细粘土组分形成第三主峰，含量约占0．52％。平均粒径Mz为28．4μm，分选系数为181，偏态为0．044，峰态为1．494，粉粘比为7．3。粒度分布显示这次哈尔滨市沙尘沉降物是迄今为止国内有见报道中最粗的，沉降物是不同来源沙尘远距离和近距离搬运的混合体，粗颗粒为低空气流搬运的近源物质。哈尔滨市或周缘邻近区域是这次特大沙尘暴的降尘中心，属大气动力条件较强的中心或近中心地带。哈尔滨城市扩展区域的疏松地表裸土、河床及漫滩细粒冲积物以及市内地表建筑沙土等都可以是哈尔滨市沙尘沉降物的主要物源。因此哈尔滨地区防治沙尘暴工作的重点应放在哈尔滨市周边沙尘源区的治理上。 相似文献
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石居里铜矿床矿石中主要矿石矿物由黄铜矿及黄铁矿等组成。铜含量一般为4％～20％，由于黄铜矿与黄铁矿复杂的嵌布关系，采用传统的老三样(丁黄药、石灰、2#油)浮选(一段磨矿，小于0．074mm占70％左右)精矿粉的铜品位仅达15．03％。造成了一定铜资源的浪费。通过对该类型铜矿石的矿物学组构及特征的研究，经多次试验后采用DY-1捕收剂及两段磨矿流程，即一段粗磨矿(小于200目即0．074mm占70％左右)丢尾，二段粗精矿再磨(小于325目即0．043mm占95％左右)后精选，使铜精矿Cu品位达20．73％，同时使硫回收率由51．26％上升到74．11％。 相似文献
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通过区内505和530等主要矿脉石英红外吸收光谱、热爆裂及热发咣特征的系统研究，总结了该区无矿、贫矿及矿体石英脉评价的石英矿物学标志，表现为：①无矿石英起爆温度为210－330℃，热爆裂曲线无明显峰型；石英热发光总强度大于20000cps，峰值强度大于500cps;②贫金石英脉其石英红外吸收相对光密度DCO2／DH2O值大于1．1；起爆温度为210－280℃，石英热爆裂曲线为明显单峰形态，主爆峰对应温度值为420－440℃；石英热发光总强度介于10000－20000cps之间，峰值强度介于150－300cps之间；③矿体石英脉其石英红外吸收相对光密度DCO2／DH2O值小于1．0；起爆温度100－160℃，热爆曲线为单峰型，主爆峰对应温度为140－180℃；石英热发光总强度值小于10000cps，峰值强度小于150cps。根据本区含金矿脉矿化分带模式及石英红外吸收光谱、热及热发光参数系统变化规律，建立了该区石英脉型金矿床找矿评价的石英矿物学标志模型。 相似文献
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陕西南郑县马元一带发现大型层控型铅锌矿带 总被引：19，自引：2，他引：19
在陕西省南郑县马元地区碑坝穹隆周缘的震旦系灯影组白云岩中发现了长大于60km、宽10-200m的铅锌成矿带。南矿化带长大于20km，宽20-120m，已圈出多条铅锌矿体；中矿化带长大于30km，宽20-200m，地表已发现多条铅锌矿体；北矿化带长大于10km，宽10-100m。主矿体长2560m，平均厚度8．60m，平均锌品位4．14％。初步认为该铅锌矿带属层控型，具有形成超大型矿床的前景。 相似文献
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颗粒级配、孔隙比是决定粗粒土渗透系数的关键因素。收集并整理得到93组粗粒土全级配（d10~d100）、孔隙比数据，采用遗传算法(genetic algorithm，GA)优化的BP(back propagation)神经网络分析和预测粗粒土渗透系数，通过平均影响值法和试验验证，评价各级配粒径对渗透系数的影响大小，探讨孔隙比对粗粒土渗透系数的影响。结果表明:d50为界限粒径，在其他粒径不变，若增大d50及以下粒径，渗透系数就增大，而增大d50以上粒径，渗透系数减小；d50及以下粒径的“细颗粒”对渗透系数的影响大于d50以上粒径的“粗颗粒”；按相对权重，d20、d80、d40属于高敏感度粒径，d10、d50、d100、d70为中敏感度粒径，d30、d90、d60为低敏感度粒径。孔隙比对渗透系数的影响大于任一特征粒径，渗透系数与孔隙比呈正相关关系；相同颗粒级配的粗粒土，随孔隙比变化可使渗透系数产生数量级跨越。采用GA-BP神经网络方法，由全级配和孔隙比能较好地预测粗粒土渗透系数。 相似文献
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可可西里马兰山冰川的近期变化 总被引：5，自引：11，他引：5
位于可可西里地区的马兰山冰帽，冰川覆盖了整个山体，冰川面积达195km^2，属极大陆型冰川，雪线海拔在5340－5540m之间，大多数冰川末端存在小冰期的碛垄，一般可分辨出3道，自小冰期以来，随着气候的变化，马兰山冰帽表现出波动退缩趋势。小冰期时，冰舌末端南坡比现在低20m，北坡低20－40m，由冰川退缩引起的冰川面积的减小相当于现代冰川面积的4．6％，略小于整个羌塘高原地区小冰期以来冰川面积减小的幅度（8％）。近百年来，冰川的退缩量为45－60m左右，而从1970年以来的30a中，马兰山冰川的退缩量为30－50m，平均年退缩量为1－1．7m。虽然小于高原边缘和其它地区冰川退缩幅度，但是退缩速率正在逐渐增大，这将对高原内陆脆弱的生态系统和生态环境产生较大的影响。 相似文献
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天然锰钾矿去除水体中苯胺的影响因素及其机制的研究表明，酸度是影响苯胺降解反应的主要因素，温度、振荡速度、矿物用量、矿物粒径及电介质浓度都不同程度地影响苯胺的降解；当介质pH值为3．0时，160～200目锰钾矿用量为10g／L、反应温度为25℃、振荡速度为200r／min、反应4h可以使50mL浓度为20mg／L的苯胺去除95％，达到工业废水一级排放标准；天然锰钾矿在酸性条件下具有强氧化性。可以使苯胺逐步降解为无机物质。以上结果都说明天然锰钾矿降解苯胺废水是一种经济有效的方法。 相似文献
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Ustinov Victor N. Mosigi Benjamin Kukui Irina M. Nikolaeva Evelina V. Campbell James A. H. Stegnitskiy Yury B. Antashchuk Michael G. 《Mineralogy and Petrology》2018,112(2):775-783
This paper presents the results of an investigation into the structure of eolian kimberlite indicator minerals (KIMs) haloes present within Quaternary Kalahari Group sediments (up to 20 m thick) overlying the Late Cretaceous kimberlites in the Orapa field in North-East Botswana. A database of more than 8000 samples shows that kimberlites create a general mineralogical blanket of KIMs of various distances of transportation from primary sources in the Orapa area. Models of the reflection and dispersion patterns of KIMs derived from kimberlite pipes including AK10/ AK22/AK23 have been revealed based on 200 selected heavy mineral samples collected during diamond prospecting activities in Botswana from 2014 to 2017. Short distance eolian haloes situated close to kimberlite bodies cover gentle slopes within plains up to 500 × 1000 m in size. They have regularly have oval or conical shapes and are characterized by the presence mainly of unabraded or only slightly abraded KIMs. A sharp reduction of their concentration from hundreds and thousands of grains / 20 l immediately above kimberlites toto 10 grains/20 l at a distance of only 100–200 m from the pipes is a standard feature of these haloes. The variation of concentration, morphology and abrasion of specific KIMs with increasing distance from the primary sources has been investigated and presented herein. Sample volumes recommended for pipes present within a similar setting as those studied, with different depth of sedimentary cover are as follows: up to 10–20 m cover at 20–50 l, 20–30 m cover at 50–100 l and 30–80 m cover at 250 l. It is important to appreciate that the discovery of even single grains of unabraded or slightly abraded KIMs in eolian haloes are of high prospecting significance in this area. The results of the research can be applied to in diamond prospecting programs in various regions with similar environments.
相似文献12.
南京周家山下蜀黄土石英颗粒特征及其物源意义 总被引：1，自引：1，他引：0
下蜀黄土的成因和物源一直是学术界研究的热点。对南京周家山下蜀黄土的石英粒度和石英表面微结构进行分析,结果显示:粉砂粒级石英颗粒（5~50 μm）占绝对优势;<20 μm组分平均含量为42.76%,<30 μm组分平均含量为62.98%;粒度分布曲线和累积曲线总体具有颗粒偏细,呈正偏态,分选较差,峰形尖锐,双峰曲线不对称的特征;粒级-标准偏差曲线呈“双峰”分布,两个明显的标准偏差峰值分别出现在7.962 1 μm和39.905 2 μm。石英颗粒表面形态主要以次棱角状为主;表面机械结构具有丰富的蝶形坑、曲脊、贝壳状断口,部分表面出现平行节理面、V形坑;不同粒级组分表面形态和机械结构特征存在差异。分析表明,南京周家山下蜀黄土属典型风成成因堆积物,是多源区物质高度混合搬运堆积的结果。 相似文献
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Mary K. Butwin Melissa A. Pfeffer Sibylle von Löwis Eivind W. N. Støren Eniko Bali Throstur Thorsteinsson 《Sedimentology》2020,67(6):3067-3087
The volcanic origin, primarily basaltic, of most of the surface material in Iceland influences its physical properties and appearance. Size distributions, shape analyses and melting experiments were made for surface material collected in high-erosion dust source areas and fresh volcanic ash deposits to determine whether they differ from one another and from dust from other major dust sources. The major differences found between Icelandic dust and dust from other major dust sources in the world, such as the Sahara, are in the particle shapes, lower density and darker colour. Icelandic dust particles greater than 20 μm retain volcanic morphological properties that are also found in fresh volcanic ash. Dust and fresh volcanic ash particles less than 20 μm are crystalline and blocky in nature, similar to the dust from other global source regions. The finer grained (<20 μm) Icelandic particles will have similar suspension and transport behaviours and be similarly hazardous to health and infrastructure as non-Icelandic dust. The coarser particles (>20 μm) will have different suspension and transport behaviours than other dusts due to the volcanic morphology. Icelandic surface material has between 5% and 30% glassy particles compared to fresh volcanic ash which has more than 50% glassy particles. Glassy particles were observed to melt at a lower temperature than the mineral grains; and, as a result, volcanic ash is found to be more threatening to aircraft engines than the typical dust from Iceland. Icelandic dust was observed to be blocky, or plate-like in the respirable size fraction, suggesting similar health hazards as dust from other regions. 相似文献
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《International Geology Review》2012,54(12):1446-1461
ABSTRACTMeta-pelitic rocks with interlayers of meta-psammites within the inner thermal aureole of the Alvand plutonic complex (Sanandaj-Sirjan Zone (SaSZ), western Iran) underwent partial melting; generating various types of migmatites. The mesosome of the Hamedan migmatites is classified into two groups: (1) cordierite-rich and Al-silicate-poor mesosomes and (2) cordierite-poor, Al-silicate-rich groups. Leucosomes are also variable, ranging from plagioclase-rich to K-feldspar-rich leucosomes. Mineral-chemical studies and thermobarometric estimations indicate temperature and pressure of 640–700°C and 3–5 kbar, respectively, for the formation of mesosomes. U–Pb zircon geochronology on 214 grains from the mesosome of migmatites indicates ages of 160–180 Ma (ca ~170 Ma) for zircon metamorphic rims and variable ages of 190–2590 Ma for the inherited detrital zircon cores. Inherited core ages show various age populations, but age populations at 200–600 Ma are more frequent. The age populations of the detrital zircons clarify that the provenance of the younger zircon grains (200–500 Ma) was more likely the Iranian plate, whereas the older grains (600 Ma to >2.5 Ga) may be sourced from both northern Gondwana (such as Arabian-Nubian Shield) and the neighbouring, old cratons like as Africa. We suggest that magmatic activities, especially mafic plutonism at ~167 Ma, are the main triggers for the heat source of metamorphism, partial melting, and migmatization. In contrast to a presumed idea for a Cretaceous regional metamorphic event in the NW parts of the SaSZ, this study attests that the metamorphism should be older and can be associated with Jurassic magmatic pulses. 相似文献
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Rajesh K. Srivastava M. Jayananda Gulab C. Gautam Amiya K. Samal 《Mineralogy and Petrology》2014,108(5):695-711
The Archean eastern Dharwar craton is transacted by at least four major Proterozoic mafic dyke swarms. We present geochemical data for the ~2.21–2.22 Ga N-S to NNW-SSE trending Kunigal mafic dyke swarm of the eastern Dharwar craton to address its petrogenesis and formation of large igneous province as well as spatial link to supercontinent history. It has a strike span of about 200 km; one dyke of this swarm runs ~300 km along the western margin of the Closepet granite. Texture and mineral compositions classify them as dolerite and olivine dolerite. They show compositions of high-iron tholeiites, high-magnesian tholeiites or picrites. Geochemical characteristics of the sampled dykes suggest their co-genetic nature and show variation from primitive (Mg#; as high as ~76) to evolved (differentiated) nature. Although geochemical characteristics indicate possibility of minor crustal contamination, they show their derivation from an uncontaminated mantle melt. These mafic dykes are probably evolved from a sub-alkaline basaltic magma generated by ~20 % batch melting of a depleted lherzolite mantle source and about 15–30 % olivine fractionation. Paleoproterozoic (~2.21–2.22 Ga) mafic magmatism is recognized globally as dyke swarms or gabbroic sill complexes in the Superior, Slave, North Atlantic, Fennoscandian and Pilbara cratons. Possible Paleoproterozoic Dharwar–Superior–North-Atlantic–Slave correlations are constrained with implications for the configuration of supercraton Superia. 相似文献
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中国东南部晚中生代俯冲带探索 总被引：38，自引：5，他引：33
根据岩浆弧位置变化追溯俯冲板块的俯冲角度变化的原理计算了１８０－８５Ｍａ时段内,古太平洋板块向欧亚大陆俯冲的俯冲角变化（从大约１０°增大至约８０°）,讨论了导致俯冲板块俯冲角变化的原因和由此引起的岩浆活动的时空变化,以及它对中国东南部地质构造的影响。 相似文献
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The provenance of Cretaceous sandstones in the Banda Arc islands differs from west to east. Sandstones in Sumba and West Timor contain significant amounts of feldspar (K-feldspar and plagioclase) and lithic fragments, suggesting a recycled to magmatic arc origin. In comparison, East Timor and Tanimbar sandstones are quartz rich, and suggest a recycled origin and/or continental affinity. Heavy mineral assemblages in Sumba and West Timor indicate metamorphic and minor acidic igneous sources and include a mixture of rounded and angular zircon and tourmaline grains. In East Timor, Babar and Tanimbar, an ultimate origin from a mainly acid igneous and minor metamorphic source is interpreted, containing a mixture of rounded and angular zircon and tourmaline grains.Detrital zircon ages in all sandstones range from Archean to Mesozoic, but variations in age populations indicate local differences in source areas. Sumba and West Timor are characterised by zircon age peaks at 80–100 Ma, 200–240 Ma, 550 Ma, 1.2 Ga, 1.5 Ga and 1.8 Ma. East Timor and Tanimbar contain 80–100 Ma, 160–200 Ma, 240–280 Ma, 550 Ma and 1.5 Ga zircon peaks. Most populations are also common in Triassic and Jurassic formations along the Outer Banda Arc and in many other areas of SE Asia. However, the abundance of Jurassic and Cretaceous populations was unexpected. We interpret Cretaceous sandstones from Sumba, Timor and Tanimbar to have been deposited in SE Sundaland. Syn-sedimentary Cretaceous (68–140 Ma) sources are suggested to include the Schwaner Mountains in SW Borneo and Sumba. Material derived mainly from older recycled sediments that had their main sources in the Bird's Head, Western and Central Australia, and local sources close to Timor. 相似文献
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低温热年代技术已经广泛应用于造山带的剥露作用和古地形演化的研究。本文对黄陵隆起进行了裂变径迹和(U-Th)/He热年代学研究,分析计算其隆升剥露速率和厚度,恢复黄陵隆起中新生代古地形。依据岩石样品冷却历史计算出的剥露速率以及剥露厚度结果,综合黄陵隆起现今地形起伏,均衡回弹作用以及古海平面变化情况,获得了黄陵隆起早侏罗世、早白垩世、晚白垩世、晚始新世以及现今5个时期的古地形变化情况。结果表明黄陵隆起地形表现为持续降低的趋势,并存在两期剧烈的隆升剥露阶段。分析认为,白垩纪(140~80 Ma±),黄陵隆起的快速隆升剥露作用与秦岭大别造山带大规模的挤压作用密切相关,晚始新世以来(40~0 Ma)黄陵隆起的快速抬升剥露作用则是对喜山期构造运动的响应。 相似文献
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Waleed Abdelmoghny Metwaly Ogila 《Environmental Earth Sciences》2016,75(24):1493
Expansive soils are considered as a potential natural hazard if they are not adequately treated. Expansive soils have high potential for shrinking and swelling under changing moisture conditions and cause extensive damages to engineering infrastructures. This study is concerned with the suitability of natural ornamental limestone dust to reduce the swelling characteristics of high expansive soils. The results are revealed that the swelling pressure and percent of heave are greatly decreased with increasing the inserted core diameters and mixing percentages of limestone dust. The average reduction percent values of swelling pressure and percent of heave are increased from 2.21% to 43.09% and from 2.56% to 45.64%, respectively, for treated soil samples with increase in limestone dust core diameters from 5 mm to 20 mm (1% to 16% of total soil area). The average reduction percent values of swelling pressure and heave percent are increased from 10.29% to 70.73% and from 22.29% to 82.90%, respectively, for treated soil samples with increase in limestone dust mixing percentages from 10% to 30%. The results are revealed that the enhancement in swelling characteristics of high expansive soils that are treated by ornamental limestone dust is mostly attributed to the replacement of high expansive fine clay particles by non-expansive and non-plastic coarse limestone dust particles, and to the presence of a considerable amount of free lime in limestone dust (4.97% as [Ca(OH)2]) that is responsible for converting the high expansive soils to less expansive soils by pozzolanic reaction. The mixing treatment method is more suitable for surficial and shallow foundation high expansive soil beds, while the compacted limestone dust piles “inserted limestone dust core method” are more suitable for deep foundation high expansive soil beds. 相似文献
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内蒙古黄岗夕卡岩型锡铁矿床辉钼矿Re-Os年龄及其地质意义 总被引：25，自引：6，他引：19
内蒙古黄岗大型夕卡岩型锡铁矿床位于大兴安岭南段黄岗梁-乌兰浩特锡铅锌铜多金属成矿带。本文利用辉钼矿Re-Os同位素定年方法对黄岗夕卡岩型矿体中5件辉钼矿样品进行了成矿年代测定,获得辉钼矿Re-Os模式年龄为134.6±2.0～136.5±1.9Ma,加权平均年龄为135.31±0.85Ma。辉钼矿Re含量高,显示有地幔物质体参与了成矿过程。大兴安岭地区成矿作用以中生代燕山期成矿为主,存在140～130Ma左右、180～160Ma左右的两次成矿爆发期,其中140～130Ma左右主要出现在岩石圈伸展减薄背景下,与燕山晚期侵入的小岩体有关的锡铅锌铜银多金属矿床;180～160Ma左右主要出现与燕山早期西伯利亚与华北板块后碰撞造山有关的钼铅锌铜金多金属矿床。黄岗锡铁矿床是在古太平洋板块俯冲大陆边缘弧后伸展环境下,发生的大规模成矿作用的产物。 相似文献