Humic substances,a possible source of environmental goitrogens

The by-products of humic substances (HS), resorcinol, orcinol, phloroglucinol, pyrogallol, 3,4- and 3,5-dihydroxybenzoic acids, and ortho- and meta-phthalic acids, have been tested for antithyroid and goitrogenic activities. By two in vitro assays all compounds, except the phthalic acids, were potent inhibitors of the thyroid peroxidase enzyme, and of thyroidal ¹²⁵I uptake and/or its incorporation into thyroid hormones using thyroid slices. Resorcinol in drinking water was goitrogenic as indicated by in vivo assay in rats. These findings, the identification of resorcinol in the water supply of an endemic goiter district in western Colombia, where increased goiter prevalence is associated with watersheds rich in organic matter, and results of elemental analysis of goitrogenic water extracts from the same district showing a composition similar to that of aquatic HS, suggest that HS degradation by-products may play an important role in the etiology of endemic goiter.     

Estimation of source parameters of Chamoli Earthquake, India

The devastating earthquake (mb = 6.6) at Chamoli, Garhwal Himalaya, which occurred in the morning hours on 29th March 1999, was recorded on Delhi Strong Motion Accelerograph (DSMA) Network operated by the Central Building Research Institute, Roorkee. In this paper the source parameters of this event calculated from the Strong Motion Data are presented. The seismic moment for this event has been found to be of the order of 10²⁵ dyne.cm and the moment magnitude has been calculated in the range of 6.53–6.69 at different stations. The stress drop and source radius for the earthquake are also calculated.     

Lithospheric stress in Mongolia,from earthquake source data

Lithospheric stress in Mongolia has been studied using mechanisms of 84 M_(LH)≥ 4 earthquakes that occurred in the 20 th century and instrumental seismic moments of 17,375 M_(LH)≥2.5 events recorded between 1970 and 2000.The M_(LH)≥ 3.5 earthquakes mostly have strike-slip mechanisms in southern and central Mongolia,with frequent reverse-slip motions in the west and normal slip in the north,especially,in the area of Lake Hovsgol.The principal stresses are,respectively,S_HS_vS_h in the center and in the south;high horizontal compression with S_HS_hS_v in the west;and a heterogeneous stress pattern with S_vS_HS_h in the north.According to seismic moments of M_(LH)=2.5 events,oblique slip generally predominates over the territory,at S_v≈S_HS_h,while frequent strike slip motions in the west record high horizontal compression(S_HS_vS_h).Earthquake mechanisms show the principal horizontal compression S_H to be directed W-E in the east,NE-SW in the central and Gobi-Altay regions,and approximately N-S in the west of Mongolia.The patterns of principal lithospheric stresses in the territory of Mongolia have undergone three events of dramatic change for a few recent decades,and these events were synchronous with three similar events in the Baikal rift system(BRS):in the latest 1960 s,latest 1970 s to earliest 1980 s,and in the latest 1980 s to earliest 1990 s.The seismicity of Mongolia has been controlled by superposition of variable stresses associated with rifting activity pulses in the neighbor BRS on the background of quasi-stationary super-regional compression.     

The Pachuca obsidian source,Hidalgo, Mexico: A geoarchaeological perspective

Sierra Las Navajas, known to archaeologists as “the Pachuca obsidian source,” has been a major source of obsidian to Mesoamerican societies for more than 3000 years, producing a fine green obsidian unique in Middle America. It was the primary source of the obsidian that formed the economic backbone of the major sociopolitical centers of Classic period Teotihuacán, epi‐Classic Toltec Tula, and Aztec Tenochtitlán. In this paper, the obsidian of Sierra Las Navajas is discussed in the following contexts: (1) geologically, because the extraordinary quality of the Pachuca obsidian, its ease of extraction, and its distinctive color and chemistry are a direct result of its geologic emplacement; (2) locally, as the different mining localities within Sierra Las Navajas reflect the varying needs of the cultures working them; and (3) globally, as the obsidians of Las Navajas were used in concert with obsidians from other sources, and were traded great distances across Mesoamerica. © 2004 Wiley Periodicals, Inc.     

崖城地区渐新统不同沉积相带烃源岩生物标志物组合特征及其烃源意义

基于40余个不同岩性烃源岩及原油饱和烃组分的GC/MS和GC/MS/MS分析资料,揭示了琼东南盆地崖城地区渐新统不同沉积相带烃源岩的生物标志物组合特征,并与崖城油气田原油进行油源精细对比,提出了新的认识。研究结果表明,海岸平原沼泽相煤及碳质泥岩呈姥鲛烷优势(Pr/Ph>5.0),三环萜烷以低碳数化合物为主(C₁₉/C₂₃>3.0),甾烷丰度低(藿烷/甾烷>5.0), C₂₉甾烷优势显著(>60%),指示高等植物为主要的有机源,且沉积于氧化环境。浅海相泥岩中Pr/Ph值大多在1.0~2.5,表征弱还原-弱氧化环境;其三环萜烷以C₂₁或C₂₃为主峰,甾烷呈"V"字型分布,藿烷/甾烷比值小于3.0,具陆源和水生双重有机质生源。煤及碳质泥岩中奥利烷和双杜松烷等陆源标志物均较少,而泥岩中却普遍富含这些化合物,反映了近岸海相沉积有机质的特殊性。因而,在近海盆地地层中奥利烷和双杜松烷丰度并不能代表总体有机质中陆源的输入比例,更可能是指相标志。通过与烃源岩的分子地球化学对比表明,崖城油气田的主体原油兼具煤成烃和泥岩所生油的生物标志物组成,为混源油,来自渐新统不同沉积相带烃源岩。     

The source of fluoride toxicity in Muteh area,Isfahan, Iran

Endemic dental fluorosis has been observed in most inhabitants of three villages of Muteh area, located in northwest of Isfahan province, with mottled enamel related to high levels of fluoride in drinking water (1.8–2.2 ppm). Forty-seven groundwater samples from six villages were collected and fluoride concentrations along with physico-chemical parameters were analyzed. Fluoride concentration in this area varies from 0.2 to 9.2 mg/l with highest fluoride level at Muteh gold mine (Chahkhatun mine). Fluoride concentration positively correlates with pH and HCO₃ ⁻ indicating that alkaline pH provides a suitable condition for leaching of fluoride from surrounding rocks. The district is mainly covered by three lithological units, namely, metamorphic and granite rocks, alluvial sediments, and carbonate rocks. Factor analysis shows that parameters can be classified into four components: electrical conductivity (EC), total dissolved solids (TDS), Cl⁻, Na⁺ and K⁺, pH and F⁻, SO₄ ²⁻and Mg²⁺, HCO₃ ⁻ and Ca₂ ⁺. The groundwaters from the three geological units were compared using Mann–Whitney U test. The order of median fluoride concentration is: metamorphic and granite rocks > alluvial sediments > carbonate rocks. Hence, the fluoride content is most probably related to fluoride-bearing minerals such as amphibole and mica group minerals in metamorphic and granitic rocks. The concentration of fluoride in drinking water wells located near the metamorphic complex in Muteh area is above 2 ppm.     

Palynofacies, palaeoenvironment, and source rocks evaluation of Ratawi Formation, Southern Iraq

Palynological analysis were done on 12 rock samples for Ratawi Formation from Rumailah well 131 and eight samples for the same formation from Zubair well 47, South Iraq, to extract sedimentary organic matters. Microscopic examination led to diagnose large numbers of spores, pollen, dinoflagellates (proximat, cavate, and chorate), foraminifera, melanogen, hylogen, and amorphogen. Three palynological facies were determined on the bases of percentages of sedimentary organic matter and palynomorphs from two sections. Analysis of these palynofacies clarified Ratawi Formation as deposited from environments ranging from delta and lagoon (suboxic–dysoxic) to shelf facies (anoxic near the shore–suboxic) with the presence of some layers deposited from semideep open marine environment (bathyal). Organic geochemical analysis of total organic carbon and Rock Eval pyrolysis were done to determine quantity, quality, and degree of maturation of the kerogen. Poor to medium proportion of total organic carbon of kerogen types II and III within a catagenesis stage are recorded in these rocks, and hence, poor hydrocarbon generation could be suggested for these strata.     

地貌演化、源-汇过程与盆地分析

地球表面的地貌演化和源-汇系统的研究是当前地球科学领域颇为关注的重要课题。围绕这些课题的研究促进了多学科的广泛交叉和合作,对沉积盆地的深入研究和发展趋势产生了深刻的影响。盆地整体地貌的演化是盆地地球动力学背景演化的直接响应。盆地内的隆-坳格局、古隆起-古斜坡地貌、同沉积构造活动形成的构造古地貌等,是盆地古地貌研究的重要内容。从陆到洋的源-汇系统由物源区、冲积-滨海平原、浅海陆架、大陆斜坡及深海等多个区域性的地貌带所组成。物源的性质与母岩组成、构造及气候作用密切相关,揭示塑造山地地貌和产生物源的构造作用和气候变量是一项长期探索的课题。陆架斜坡至深海区是从陆到洋的源-汇系统的最终沉积区,其研究长期受到高度关注。大型内陆湖盆存在的源-汇系统,包括物源区、冲积平原、滨-浅湖、最后为深湖的多级地貌单元。构造活动的内陆碎屑湖盆中以近且多方向物源、构造差异活动明显、汇水盆地小、沉积物类型对气候变化响应敏感等为特征。依据物源区、沟谷(水道)及沉积体系类型划分的源-汇体系类型的研究,包括盆内古隆起形成的局部的源-汇过程,对盆地的沉积充填过程和沉积分布具有重要意义。基于高分辨率三维地震数据的地震地貌或地震沉积学分析,为地下沉积体系的沉积地貌和沉积过程的研究提供了最重要的手段。     

Upper mantle source for some hawaiites,mugearites and benmoreites

Chemical analyses of over seventy lavas or dykes containing spinel lherzolite inclusions of high pressure mineralogy, show that most host magmas are of alkali olivine basalt or basanite composition with relatively rare olivine nephelinites, and olivine melilitites. The 100 Mg/Mg+Fe⁺⁺ ratios of host magmas display a strong maximum at about Mg₇₀ consistent with partial melting of source peridotite with olivine of Fo_88–90. In contrast to these primary magmas, there occur some host magmas with 100 Mg/Mg+Fe⁺⁺<60 and with chemical compositions resembling those of classical hawaiite, mugearite, and nepheline benmoreite magmas. It is inferred that these magmas have been produced by crystal fractionation, within the upper mantle, of parental basanites or alkali olivine basalts. The presence of kaersutitic hornblende xenocrysts accompanying the lherzolite inclusions, and the nature of the chemical variation between associated basanites and nepheline benmoreites suggests that crystal fractionation has been dominated by kaersutitic hornblende, together with olivine and, in some cases, probably clinopyroxene. The mantle-derived nepheline benmoreite magmas also show similarities to some plutonic nepheline syenites.     

Simulated impacts of artificial groundwater recharge and discharge on the source area and source volume of an Atlantic Coastal Plain stream, Delaware, USA

A numerical groundwater-flow model was used to characterize the source area and volume of Phillips Branch, a baseflow-dominated stream incising a highly permeable unconfined aquifer on the low relief Delmarva Peninsula, USA. Particle-tracking analyses indicate that the source area (5.51 km²) is ～20% smaller than the topographically defined watershed (6.85 km²), and recharge entering ～37% of the surface watershed does not discharge to Phillips Branch. Groundwater residence time within the source volume ranges from a few days to almost 100 years, with 95% of the volume “flushing” within 50 years. Artificial discharge from groundwater pumping alters the shape of the source area and reduces baseflow due to the interception of stream flow paths, but has limited impacts on the residence time of groundwater discharged as baseflow. In contrast, artificial recharge from land-based wastewater disposal substantially reduces the source area, lowers the range in residence time due to the elimination of older flow paths to the stream, and leads to increased discharge to adjacent surface-water bodies. This research suggests that, in this and similar hydrogeologic settings, the “watershed” approach to water-resource management may be limited, particularly where anthropogenic stresses alter the transport of soluble contaminants through highly permeable unconfined aquifers.     

The earthquake of March 4, 1977, its recording peculiarities and source parameters

A detailed analysis of recording peculiarities at seismic stations of the Uniform System of Seismic Observations (USSO) is presented a complicated nature of the source being shown. Consideration is given to parameters of the earthquake source, including the seismic moment and the length of the rupture.Comparison of magnitudes M_LH and M_PV indicates an anomalous attenuation in surface waves, itis is 3–4 times weaker than it had been noticed in case of other intermediate-depth Carpathian earthquakes.On the basis of comparison of the logarithm of the ratio of P-wave spectra at different epicentral distances (30° –70° ), the fac tor characterizing the absorption of P wave is found to remain practically unchanged.Average value of the seismic moment is estimated to be 2.6 × 10²⁷ dyne × cm, the most reasonable length of the rupture 58 km, and its focus 100 –130 km. The source parameters of the earthquake in question are compared with those of the earthquake of November 10, 1940.     

Serpentinites as a possible source of the Adola placer gold,Sidamo, Ethiopia

It is proposed that the Adola placer gold was derived, ultimately, from the ultrabasic rocks which are now represented by serpentinites and talc-schists. During the process of serpentinisation the ultrabasic rocks expelled abundant silica and available gold, which were deposited as gold-quartz veins in the overlying brittle basalts. Erosion of these basalts, now amphibolites has resulted in concentration of the gold as placers in the overlying conglomerates and soils.     

Hydrocarbon source potential of the Proterozoic Sirban Limestone Formation,NW Himalaya,Jammu

The Proterozoic Sirban Limestone Formation (SLFm) crops out as detached allochthons in the northwest Himalaya (Jammu region, India) and has its coeval equivalents laterally disposed in the west in Salt Range, in the northwest in Abbotabad (Pakistan) and in southeast in Himachal Pradesh (India). The oil and gas occurrences have been reported from the Proterozoic successions globally and the hydrocarbon potential of the SLFm cannot be ruled out.The interbedded shales and algal laminated dolostones within the SLFm have yielded microflora comparable to those reported in the North African Neoproterozoic sandstones and the Late Proterozoic carbonates of the giant oil and gas fields of the Siberian Platform. The SLFm contains a rich and diverse biota comprising ~ 10% of the rock volume in thin section. The rich organic assemblage justified a hydrocarbon source potential analysis of the SLFm, tested in this study by Rock Eval (RE) pyrolysis.RE pyrolysis yielded a total organic carbon (TOC) content of 0.02 to 1 wt. % with very low Hydrogen Index (HI) values for the shales and TOC content averaging 0.02 wt. % for the dolostones. The organically lean shales and dolostones exhibit T_max values indicative of immature to post mature stage. But, since these values are for the samples with complex thermal and tectonic history the results may be unreliable. The highly altered organic matter and kerogen present in the SLFm had the potential to generate hydrocarbons and presently indicates no significant source potential. This study is important for understanding the hydrocarbon occurrences in the SLFm particularly in light of the recent oil and gas discoveries from the coeval Proterozoic successions.     

Petrology,geochemistry and source characteristics of the Burpala alkaline massif,North Baikal

The Burpala alkaline massif contains rocks with more than 50 minerals rich in Zr,Nb,Ti,Th,Be and rare earth elements(REE).The rocks vary in composition from shonkinite,melanocratic syenite,nepheline and alkali syenites to alaskite and alkali granite and contain up to 10%LILE and HSFE,3.6%of REE and varying amounts of other trace elements(4%Zr,0.5%Y,0.5%Nb,0.5%Th and 0.1%U).Geological and geochemical data suggest that all the rocks in the Burpala massif were derived from alkaline magma enriched in rare earth elements.The extreme products of magma fractionation are REE rich pegmatites,apatite-fiuorite bearing rocks and carbonatites.The Sr and Nd isotope data suggest that the source of primary melt is enriched mantle(EM-Ⅱ).We correlate the massif to mantle plume impact on the active margin of the Siberian continent.     

宜万铁路马鹿箐隧道岩溶突水来源分析

马鹿箐隧道是宜万铁路22座长、特长隧道之一,全长7 879m,最大埋深600m。2006年1月21日发生特大突水事故,最大突水量达30×104m3/h,造成重大损失。为查明突水来源,在突水区附近约5km2范围内采集不同类型的水样21个,淤泥样2个,采用水文地球化学方法对这些水样进行水化学分析和同位素分析,还对淤泥和部分水样做了14C测年。通过对比样品分析结果,运用水文地球化学理论和同位素水文地质方法,认为突水来源为年代较老的溶洞封存水。     

广州市花都区地下水应急水源地研究

广州市花都区地下水资源较丰富,根据地下水的赋存条件,地下水类型划分为松散岩类孔隙水、碳酸盐岩裂隙岩溶水、红层孔隙裂隙水、层状岩类裂隙水及块状岩类裂隙水。其中供水意义较大的地下水类型为松散岩类孔隙水和碳酸盐岩裂隙溶洞水。依据应急水源地圈定依据,圈定四处地下水应急水源地,对潜在供水能力、水质及地下水开采风险进行评价。结果显示:各应急水源地地下水水质总体良好,经相应处理后可满足应急供水水质需求,地地下水开采风险主要有地质灾害风险、地下水污染风险及开采技术风险。应急状态下,各水源地地下水总允许开采资源为72 119.13 m^3/d,可满足花都区63.86%常住人口的应急供水。     

新疆伊宁盆地石炭系阿克沙克组烃源岩特征

从纵向展布、有机质丰度、类型及热演化特征等方面分析了新疆伊宁盆地下石炭统阿克沙克组烃源岩特征。石炭系阿克沙克组烃源岩分布集中,厚度较大,阿克沙克剖面累计厚度达202.1m,总有机碳(TOC)含量平均为1.19%;干酪根类型为Ⅱ1型;镜质体反射率(Ro)平均为1.56%,表明干酪根演化进入高成熟阶段。综合评价认为,下石炭统阿克沙克组具有较好的生烃条件,伊宁盆地石炭系具有良好的油气资源前景。     

Geology,geochemistry, and source characteristics of Neoproterozoic arc-related clastic metasediments,Central Eastern Desert,Egypt

The present work concerns two occurrences of Neoproterozoic volcaniclastic metasediments in the Central Eastern Desert (CED) of Egypt namely Alam occurrence and Atalla occurrence. They are mainly composed of bedded successions of feldspathic and feldspathic-lithic metagreywackes, arkosic metagreywackes, metasiltstones, and subordinate metaconglomerates. The rocks have been subjected mainly to various ductile deformational events (D₁ and D₂) due to NE–SW compression and later deformation (D₃). The D₁ deformation is synchronous with greenschist facies metamorphism (M₁). The Alam metagreywackes show oceanic arc tectonic setting. The greywackes have clasts of quartz, feldspar, and metamorphic amphibole after pyroxene and show variable abundances of Cr, Ni, and V. Their provenance components are mainly of evolved felsic and mafic (bimodal) island arcs. The rocks are suggested to be deposited in a localized “intra-arc basin.” The metagreywackes of Atalla show tectonic setting affinity similar to continental sland arc or active continental margin. Their geochemical characteristics reflect the presence of felsic rocks as the main sources, together with minor inputs of intermediate rocks and reworked mineral grains of quartz and feldspar. They are deposited in a localized “retro-arc basins” of an active continental margin. The whole sequences of both Atalla and Alam sediments have been subjected to deformation and contemporaneous regional metamorphism during arc-arc or arc-continent collision. Newproterozoic clastic metasedimentary rocks in the CED appear to have been deposited in arc-related basins, including interarc or back-arc basins, intra-arc basins, and retro-arc basin of active continental margin.