琼北马鞍岭地区第四纪火山活动期次划分

琼北马鞍岭地区第四纪火山活动具有多期性。据火山作用方式、火山形貌及风化程度、火山喷发产物与沉积地层以及火山机构之间的相互叠置关系 ,结合同位素年龄 ,可分为德义岭、道堂、杨花、雷虎岭、昌道和马鞍岭等 6期 ,其中德义岭期为中更新世 ,道堂和杨花期为晚更新世 ,雷虎岭、昌道和马鞍岭期属全新世。不同期次具有不同的火山活动方式、喷发强度及火山结构类型。德义岭期火山活动以溢流为主 ,火山锥为低缓的熔岩穹丘。杨花期为射气岩浆爆发作用形成的低平火山。雷虎岭与马鞍岭期主要形成由碎屑锥和熔岩流组成的夏威夷式火山 ,熔岩流构造类型以结壳熔岩为主     

长白山天池火山玻璃和长石微观特征研究

研究了长白山天池火山1000年和5000年前2次大喷发产生的浮岩和火山灰的微观特征,通过TEM-EDX和SEM-EDX分析了浮岩中的火山玻璃和长石晶屑的表面特征及风化层厚度。5000年前大喷发浮岩中的火山玻璃风化层平均厚度3·74μm,1000年前大喷发为0·98μm;5000年前大喷发浮岩中的长石表面风化溶蚀度大于1000年前大喷发物中的长石;两次大喷发浮岩中的火山玻璃风化层化学组成与火山玻璃相比富Al和Fe而Si减少。综合上述特征认为,天池火山喷发物中矿物的微观特征的差异与火山喷发年代和喷发环境有关。因此,系统研究天池火山喷发物的微观特征是十分必要的,并且具有一定的应用价值     

镜泊湖全新世火山空降碎屑剖面和喷发历史

镜泊湖全新世火山群 10余座火山分成 5个小的喷发中心位居西南和东北两区 ,每个喷发中心由 2～ 4个火山组成。西南区包括“火山口森林”、“大干泡”、“五道沟”和“迷魂阵”等 4个喷发中心 ,东北区仅“蛤蟆塘”1个喷发中心。火山喷发的产物主要包括熔岩流、溅落堆积和空降堆积 ,火口的锥体主要由溅落堆积的火山渣、火山弹、熔岩饼和薄层熔岩流组成。在“大干泡”和“蛤蟆塘”两处的空降碎屑堆积可达数米厚。镜泊湖全新世火山岩分布面积近 5 0 0km2 ,岩浆主要源自“火山口森林”的1号和 4号火口。文中通过“火山口森林”4号火口空降碎屑实测剖面及其碳化木14 C定年 ,纠正了以往的14 C定年资料 ,认为镜泊湖全新世火山的喷发活动主要在距今 5 2 0 0～ 5 5 0 0a,相继由多次喷发形成 10余座火山。研究认为 ,镜泊湖地区全新世期间不存在以千年计的 3期火山喷发活动     

长白山天文峰剖面全新世火山喷发物长石风化溶蚀特征及地质意义

利用扫描电镜和能谱分析研究了长白山天池火山天文峰剖面全新世喷发物中长石表面风化溶蚀显微形貌和化学组成,结果显示: 天文峰剖面从顶部黑色浮岩向下到暗灰色浮岩中,长石表面发育风化溶蚀不同的显微形貌结构。其特征有,风化初期的溶蚀作用主要在双晶缝、解理缝等结构薄弱部位,形成规模较小的溶孔和溶缝等,随着风化溶蚀程度的增加,已经形成的溶蚀痕迹进一步扩大、合并、相互贯通而形成矩形溶孔或棱柱状溶孔。长石晶体上溶蚀痕迹的扩大受长石晶体各向异性的控制。天文峰剖面火山喷发物时代越早,长石颗粒表面风化溶蚀程度越强,结构越复杂; 火山喷发物时代越晚,长石颗粒表面风化溶蚀程度越弱,结构越简单。即长石表面风化溶蚀程度与火山喷发的时代具有一定的相关性。根据长石颗粒表面的显微形貌结构,认为漫江林场浮岩与天文峰剖面中灰色浮岩应是火山同一次喷发的产物。长石表面风化溶蚀度可以作为判定火山喷发精细序列的一个代用指标。能谱分析显示,较新鲜的长石表面与风化溶蚀的长石化学组成不同。长石风化溶蚀的显微形貌和化学组成反映了它是天然风化、溶解、淋滤,最后又有物质沉淀的自然成因。Fe元素则可能与微生物作用有关。详细研究长石表面的风化溶蚀特征,它将有可能成为从岩石微观方面探讨火山喷发后环境变化和火山喷发期次的一种新方法。     

火山喷发物的显微构造研究及其地质意义

火山喷发物及其显微结构特征记录了喷发之前岩浆体中物理、化学过程的信息,喷发时的爆炸程度、岩浆与地下水的相互关系、在地表的侵位方式(如熔岩流、火山灰空降或火山碎屑流),以及在喷发后期风化特征等有关信息。因此,通过对火山喷发产物的显微构造研究,可以获得许多由宏观研究所无法获得的有关岩浆喷发前、喷发期间和喷发后的作用过程的重     

琼北火山区流体地球化学特征及近期火山喷发危险性评估

琼北火山区地下流体地球化学调查结果显示 ,目前马鞍岭火山附近较大范围内深层地下水仍有一定强度的深源CO2 释放活动 ,火山口附近地下水的Na含量也相对偏高。地球化学异常指示马鞍岭、雷虎岭等火山可能仍属于休眠火山 ,应继续关注。但从整体上看 ,琼北火山区深源流体释放活动的强度较弱 ,因此区内近期尚没有火山喷发活动的危险     

黑龙江省科洛火山群火山地质研究

科洛火山群的新生代火山共有23座,坐落于科洛河两岸,火山岩面积约为350km2,岩性主要为碱性玄武岩.由于地处NE向断陷盆地这一特殊的构造位置,科洛地区的火山活动及展布主要受到区域基底断裂的制约.火山喷发形式总体为中心式,属斯通博利式火山.火山活动可划分为上新世、更新世和全新世3期.上新世在断陷盆地边缘形成了一系列NE向线性展布的中心式溢出型火山,其中部分火山因风化剥蚀而失去了原有的火山地貌特征,仅保留盾形熔岩台地.早更新世火山活动相对平静.中-晚更新世火山活动仍受到NE向基底断裂的控制,但喷发中心、喷发方式及喷发强度均发生改变,火山由碱玄质火山渣锥和熔岩流组成.进入全新世以后南山喷发,其火山结构保存完好,裸露的熔岩台地保留了较好的微地貌特征.该期火山亦由碱玄质火山渣锥和熔岩流构成.在科洛火山群的火山活动过程中,其熔岩流覆盖了早期沉积地层,并对盆地中的河流进行了改造,最终导致该区断陷盆地初始地貌的改变.     

五大连池火山1720-1721年喷发观测记录

存于黑龙江将军衙门档案中的五大连池火山喷发满文史料 (由吴雪娟发现并译成汉文 ) ,详细记载了五大连池火山在 172 0年 1月 14日至 172 1年 3月 18日喷发形成老黑山、172 1年 4月 2 6日至 172 1年 5月 2 8日喷发形成火烧山的全部过程 ,记述了这 2座火山的喷发时间、地点、喷发状态和火山堰塞湖形成以及参加观测的人员情况等各种史实。这是中国历史上迄今为止对火山喷发仅有的一次有组织的观测活动 ,这些记录为火山观测研究提供了珍贵的第一手资料。同时 ,也表明中国是世界上火山观测开展较早的国家之一。以往认为五大连池老黑山、火烧山火山喷发的时间为公元1719— 172 1年 ,实际应为公元 172 0— 172 1年     

海口地区火山活动初步研究

海口地区的马鞍岭-雷虎岭火山群是中国为数不多的几个休眠火山群之一。通过对区域火山活动期次划分、深部岩浆囊探测以及对火山类型、规模、物质组成和溶岩覆盖面积的分析,总结了海口地区火山活动的时、空、强特征。结合对火山区地震、地磁、体应变和地热等观测资料的分析,对火山区深部岩浆活动的状态进行了初步评估。研究认为海口全新世火山区最后一次火山喷发距今约4 000a左右,其现今火山活动已趋于平静,未来的火山活动可能向1605年琼州7.5级大地震震中区迁移     

长白山天池火山碎屑流灾害区划

在回顾总结了国外火山碎屑流灾害分析模型研究历史的基础上,本文选取了Flow3D模型对我国东北地区长白山天池火山未来大喷发可能产生的火山碎屑流进行了灾害区域划分。以长白山天池火山现代地形为依据,设定了11条未来爆炸式火山喷发时产生的火山碎屑流的可能流动线路。模拟结果表明,在喷发柱高度为10km的情况下,灾害区划最大半径为13.7km;在喷发柱高度为20km的情况下,灾害区划最大半径为35.4km;在喷发柱高度为30km的情况下,灾害区划最大半径为57.8km。在此基础上,得出了长白山天池火山未来发生中规模、大规模和超大规模火山喷发时火山碎屑流的覆盖范围,完成了我国第一幅长白山天池火山碎屑流灾害区划图。     

Structure of weathered clastic crust and its petroleum potential

Weathered clastic crust can be subdivided into weathered clay and leached zone in terms of variable weathering of different minerals and mobility of weathered products.On the basis of clastic outcrops and well cores in the Junggar Basin,the dark red Fe-rich weathered clay is formed in an arid environment,whereas the light blue Al-rich weathered clay under humid conditions.According to the geochemical analysis,a new weathering index for weathered clastic crust is built mainly on Fe and Al contents,accurately indicating the weathered clay,sandy leached zone,and muddy leached zone in the Junggar Basin.The breaking pressure of weathered clay is rather large,the same as that of normal muddy cap,effectively to seal oil or gas.The porosity of underlying leached zone is greatly enhanced by weathering and leaching,but its permeability is a function of clay mineral content,i.e.,the higher the clay content,the worse the permeability.Weathered crust provides effective sealing conditions for both top and bottom layers of a petroleum reservoir,and is important in the clastic hydrocarbon exploration.     

REE and (э)Nd of clay fractions in sediments from the eastern Pacific Ocean: Evidence for clay sources

Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and 143Nd/144Nd. Montmorillonite/illite ratio (M/I ratio), total REE contents ((REE), LREE/HREE ratio and cerium anomaly (бCe) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio >1, бCe (0.85, (REE (400 μg/g, LREE/HREE ratio (4, and REE patterns similar to those of pelagic sediments are terrigenous and autogenetic mixed clay fractions and contain more autogenetic montmorillonite. Clay fractions with M/I ratio <1, бCe=0.86 to 1.5, ΣREE=200 to 350 μg/g, LREE/HREE ratio (6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The 143Nd/144Nd ratios or (э)Nd values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to (э)Nd values. Terrigenous clay minerals of type I with the (э)Nd values of -8 to -6 originate mainly from North American fluvial deposits. Those of type II with the (э)Nd values of -9 to -7 are mainly from the East Asia and North American fluvial deposits. Those of type III with (э)Nd values of -6 to -3 could come from the central and eastern Pacific volcanic islands. Those of type IV with (э)Nd values of -13 to -12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific.     

江西九庐公路红土剖面的磁学特征及其反映的风化成土作用

南方第四纪红土是研究古环境变化的重要载体.本文对采自江西九江的九庐公路红土剖面进行了详细的环境磁学研究,拟探讨多项磁参数在提取南方红土古环境信息方面的价值.结果显示,红土剖面上段的弱风化层,磁化率随着成土作用的增强而增大,反映了成土过程中产生的细颗粒亚铁磁性矿物导致的磁化率增加;而在剖面下段强风化的网纹红土层,表现为磁...     

East Asian paleoclimate change in the Weihe Basin(central China)since the middle Eocene revealed by clay mineral analysis

Obtaining a continuous sedimentary record of Cenozoic East Asian paleoclimate change is key to understand the origin, evolution and driving mechanism of the East Asian monsoon and climate change. Based on the continuous Cenozoic fluvial and lacustrine sedimentary sequence in the Weihe Basin, central China, we carried out research on the content and crystal parameters of clay minerals. The paleoclimate change since the middle Eocene was reconstructed accordingly. The results show that smectite and illite are the dominant clay minerals in fluvial-lacustrine sediments of Weihe Basin. The crystallinity of illite,the chemical index of illite, the ratio of smectite to illite and chlorite decrease gradually, which indicates that chemical weathering in the Weihe River watershed stepwise weakened since the middle Eocene, under the background of a semi-arid and semi-humid climate. The formation of palygorskite may be affected by a weak diagenesis. In this case, the content of smectite and the illite crystallinity caused by the weathering in the corresponding period may be actually higher than that of the current,which indicates that the climate in the Weihe Basin region was relatively warm and humid from the middle Eocene to Pliocene.With the decrease of Cenozoic global temperature and the continuous accumulation of sediments, the intensity of chemical weathering in the Weihe Basin gradually weakened, and the East Asian monsoon climate gradually evolved until becoming dry in the Quaternary. Evidence from clay minerals also indicates that the aridification in the Weihe Basin from the late Eocene to the Oligocene may be a response to the global cooling event at the Eocene-Oligocene transition.     

Meteoric 10Be speciation in subglacial sediments of East Antarctica

A sequential chemical extraction procedure was developed and tested to investigate the utility of meteoric ¹⁰Be as a tracer for authigenic mineral formation beneath the East Antarctic Ice Sheet. Subglacial meltwater is widely available under the Antarctic Ice Sheet and dissolved gases within it have the potential to drive chemical weathering processes in the subglacial environment. Meteoric ¹⁰Be is a cosmogenic nuclide with a half-life of 1.39·10⁶ years that is incorporated into glacier ice, therefore its abundance in the subglacial environment in Antarctica is meltwater dependent. It is known to adsorb to fine-grained particles in aqueous solution, precipitate with amorphous oxides/hydroxides, and/or be incorporated into authigenic clay minerals during chemical weathering. The presence of ¹⁰Be in chemical weathering products derived from beneath the ice therefore indicates chemical weathering processes in the subglacial environment. Freshly emerging subglacial sediments from the Mt. Achernar blue ice moraine were subject to chemical extractions where these weathering phases were isolated and ¹⁰Be concentrations therein quantified. Optimization of the phase isolation was developed by examining the effects of each extraction on the sample mineralogy and chemical composition. Experiments on ¹⁰Be desorption revealed that pH 3.2–3.5 was optimal for the extraction of adsorbed ¹⁰Be. Vigorous disaggregation of the samples before grain size separations and acid extractions is crucial due to the incorporation of the nuclide in clay minerals and its preferential absorption to clay-sized particles. ¹⁰Be concentrations of 2–22·10⁷ atoms·g⁻¹ measured in oxides and clay minerals in freshly emerging sediments strongly indicate subglacial chemical weathering in the catchment of the Mt. Achernar moraine. Based on total ¹⁰Be sample concentrations, local basal melt rates, and ¹⁰Be ice concentrations, sediment-meltwater contact in the subglacial environment is on the order of thousands of years per gram of underlying fine sediment. Strong correlation (R = 0.97) between ¹⁰Be and smectite abundance in the sediments supports authigenic clay formation in the subglacial environment. This suggests meteoric ¹⁰Be is a useful tool to characterize subglacial geochemical weathering processes under the Antarctic Ice Sheet.     

Clay mineralogy of the first and second members of the Nenjiang Formation,Songliao Basin: Implications for paleoenvironment in the Late Cretaceous

The first and second members of the Nenjiang Formation (K₂n¹⁺²) in the Songliao Basin, northeast China, are an interval of dark-colored mudstone. Paleoenvironmental studies of these strata are useful for understanding the terrestrial environment under a greenhouse climate and hydrocarbon accumulation in lake basins. In this study, clay mineralogy of the K₂n¹⁺² from four borehole or outcrop sections is investigated to understand terrestrial paleoenvironment during the depositional period in the Late Cretaceous. In the mudstone samples, smectite and illite are the predominant clay minerals, and were derived from weathering of parent rocks in a temperate, sub-humid to sub-arid climate; kaolinite and chlorite are minor clay species. The difference in the clay-mineral assemblages between the eastern and western margins of the basin was primarily controlled by provenance lithology, and the high smectite content in the western basin resulted from alteration of volcanic rocks exposed in the Greater Xing’an Range area. The increasing illite content and ratio of illite/smectite percentages in the upper part of the first member of the Nenjiang Formation indicate paleoenvironmental change. This temporal change in the clay-mineral composition was primarily caused by a regionally cooler and drier paleoclimate, consistent with previous paleoenvironmental reconstructions.     

Hydrothermal alteration and earth surface rock weathering: A basalt example

Geomorphologists have not devoted sufficient attention to the formation of clay minerals by hydrothermal activity. This paper describes the breakdown of freshly-quarried basalt by cyclic wetting and drying. Breakdown is attributed to the swelling of hydrothermally-derived smectite, and it is argued that the effects of endogenic processes can exert a significant control upon weathering behaviour under earth surface conditions.     

Geochemistry and mineralogy of the Late Permian coals from the Songzao Coalfield, Chongqing, southwestern China

Mineralogy and geochemistry of the four main workable coal seams (No.6, No.7, No.8, and No.11) of Late Permian age from the Songzao Coalfield, Chongqing, Southwest China, were examined using in- ductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), cold-vapor absorption spectrometry (CV-AAS), ion-selective electrode (ISE), scanning electron mi- croscopy equipped with an energy-dispersive X-ray spectrometer (SEM-EDX), and X-ray diffraction analysis (XRD). The results showed that the main workable No.8 Coal that accounts for about 60% of the total coal reserves in the Songzao Coalfield was not enriched in hazardous trace elements. The No.11 Coal has high concentrations of alkaline elements, Be (9.14 μg/g), Sc (12.9 μg/g), Ti (9508 μg/g), Mn (397 μg/g), Co (23.7 μg/g), Cu (108 μg/g), Zn (123 μg/g), Ga (32 μg/g), Zr (1304 μg/g), Nb (169 μg/g), Hf (32.7 μg/g), Ta (11.4 μg/g), W (24.8 μg/g), Hg (0.28 μg/g), Pb (28.1 μg/g), Th (24.1 μg/g), and rare earth elements (509.62 μg/g). The concentration of Nb and Ta in the No. 11 Coal is higher than the industrial grade, and their potential utilization should be further studied. Besides pyrite, quartz, calcite, and clay minerals, trace minerals including chalcopyrite, marcasite, siderite, albite, mixed-layer clay minerals of illite and smectite, monazite, apatite, anatase, chlorite, and gypsum were found in the No.11 Coal. It should be noted that alabandite of hydrothermal origin and anatase occurring as cement were identi- fied in coal. In addition, the clayey microbands derived from alkaline volcanic ashes were identified in the coal. The dominant compositions of these clayey microbands were mixed-layer clay minerals of illite and smectite, which were interlayered with organic bands. The modes of occurrence of alkaline volcanic ash bands indicate that the volcanic activities were characterized by the multiple eruptions, short time interval and small scale for each eruption during peat accumulation. The alkaline volcanic ashes were the dominant factors for the enrichment of alkaline elements, Nb, Ta, Zr, Hf, and rare earth elements, and the sulfide minerals are the main carriers of Ga, Cu, and Hg in the No. 11 Coal.     

Volcanic soil formation in Calabria (southern Italy): The Cecita Lake geosol in the late Quaternary geomorphological evolution of the Sila uplands

This paper focuses on the main morphological, physical, chemical and mineralogical features of an andic-like soil, widely outcropping in the Sila upland plateau of Calabria (southern Italy), and its potential role in tephrostratigraphy. A multidisciplinary and multiscale approach allowed identification of this soil as a “masked” distal archive of volcanic products, developed on granite rocks and sediments with a coeval pyroclastic input during pedogenesis. The study demonstrates that the contribution of volcanic parent materials can be successfully hypothesized and assessed even in the absence, limited extent or poor preservation of primary eruptive products. The soil has an Andisol-like appearance, despite laboratory data that do not match the entire suite of diagnostic criteria for the Andisol taxonomic order. Geomorphological, stratigraphic and pedologic results, coupled with tephrostratigraphic and radiometric data, concur to suggest a Late Pleistocene(?) to Holocene age of the Andisol-like soil. In particular, the rhyolitic chemical composition of small-sized glass fragments (identified by SEM–EDS analyses) indicates soil genesis contributed by volcanic ash, probably sourced from Aeolian Arc explosive activity spanning the last 30 ka. Accordingly, the evidence of limited relict clay illuviation and the specific type of pedogenesis allowing the development of andic properties (in turn related to the neoformation of clay minerals from the weathering of volcanic glass) are consistent with a climatic shift from a seasonally-contrasted to a constantly humid pedoenvironment. This change can be ascribed to the Lateglacial(?) or Early–Middle Holocene to Late Holocene transition. Calibrated AMS ¹⁴C dates performed on charcoal fragments sampled from three representative soil profiles, provide Late Holocene ages (3136 ± 19, 343 ± 16 and 92 ± 24 yr BP), in accord with archaeological finds. On the basis of the consistent stratigraphic position, lateral continuity and wide extent, the soil can be considered a good pedostratigraphic marker in the Sila highlands and is informally defined as the “Cecita Lake geosol”. It supplies valuable time constraints for the underlying (occasionally overlying) deposits and/or soils. Moreover, it allows regional-scale morphostratigraphic correlations and detailed reconstruction of Late Pleistocene–Holocene geomorphic events in Calabria, a very suitable region for distal tephra deposition in the central Mediterranean peri-volcanic area. The effects of high-energy volcanic eruptions are interfingered with or superimposed by other geomorphic processes and climatic or anthropogenic signals.     

火山岩风化壳地层型油气藏评价预测方法研究——以新疆北部石炭系为例

针对火山岩风化壳地层型油气藏强非均质性,评价预测难度大,勘探成功率低等难题,本文采用重磁电剥层处理、沿层延拓信号增强反演方法有效顶测区域火山岩分布;建立风化淋滤剥蚀后不同岩石组合的不完整火山机构和形态识别模式,利用相干体和振幅分析等方法有效识别火山岩目标;在建立单次火山喷发岩石序列及储层分布模式基础上,开发了基于次生溶...