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21.
L. Valenzuela-Vásquez J. Ramírez-Hernández J. Reyes-López A. Sol-Uribe O. Lázaro-Mancilla 《Environmental Geology》2006,51(1):17-27
Anomalous high fluoride concentration up to 7.59 mg/dm3 is found in groundwater from “La Victoria” area. This water is used to supply drinking water to Hermosillo City, Sonora. Geochemistry of groundwater, relationship between physicochemical parameters, hydrogeology and geologic setting were correlated to define the origin and the geochemical mechanisms of groundwater fluorine enrichment. High fluoride concentration is associated with high bicarbonates, pH and temperature, and it decreases toward the west and south of the area. Fluoride is in negative correlation to calcium concentration. Sodium sulphate facies of regional deep water flow are related to high fluoride concentration. High electric resistivity rocks associated with granites from the Sierra Bachoco basement might be the deep source of fluoride. Outcropping of Sierra Bachoco in the west causes upward regional flow. Groundwater of longer residence time can be pumped there. The anomalous area is restricted to “La Victoria” because calcareous paleozoic rocks outcrop to the south. 相似文献
22.
用质子诱发γ－射线发射技术（ＰＩＧＥ）测量了甘肃、青海、宁夏和内蒙古四省区的６０个古动物骨骼和牙齿化石中的氟含量，得到与地质年代有较明显的相关性的结果，为氟含量测定地质年代提供了一组较系统的数据，显示出该方法有较大的应用前景。如果考虑围岩对化石氟含量的影响等因素，有可能得到更满意的结果。 相似文献
23.
Apatite is a cumulate phase in the upper parts of some mafic layered intrusions and anorthositic complexes. We investigated the effect of pressure and fluorine on apatite saturation in mafic magmas to better understand under which conditions this mineral crystallizes. Apatite saturation gives information about the formation of silicate rocks, and is of interest in explaining the formation of apatite–oxide-rich rocks (e.g. nelsonites comprising approximately, one-third apatite and two-third Fe–Ti oxide). Two models of formation are proposed for this rock type: crystal fractionation followed by accumulation of apatite and Fe–Ti oxides and liquid immiscibility. New experiments carried out with mafic compositions at 500 MPa confirm that the most important variables on phosphate saturation are SiO2 and CaO. Fluorine addition leads to apatite saturation at lower SiO2 and higher CaO concentrations. Comparison of our results with those of previous experimental studies on liquid–liquid immiscibility at upper-to-mid-crustal conditions allows us to investigate the relative importance of apatite saturation versus liquid–liquid immiscibility in the petrogenesis of nelsonites and similar rocks. The liquid line of descent of three natural examples studied (the Sept-Îles intrusive suite, the anorthositic Complex of the Lac-St-Jean and the Skaergaard layered intrusion) do not cross the liquid–liquid immiscibility field before they reach apatite saturation. Thus, the apatite–oxide-rich rock associated with these three intrusive suites are best explained by crystal fractionation followed by accumulation of apatite and Fe–Ti oxides. 相似文献
24.
B,As, and F contamination of river water due to wastewater discharge of the Yangbajing geothermal power plant,Tibet, China 总被引：5，自引：0，他引：5
Thermal waters from the Yangbajing geothermal field, Tibet, contain high concentrations of B, As, and F, up to 119, 5.7 and
19.6 mg/L, respectively. In this paper, the distribution of B, As, and F in the aquatic environment at Yangbajing was surveyed.
The results show that most river water samples collected downstream of the Zangbo River have comparatively higher concentrations
of B, As, and F (up to 3.82, 0.27 and 1.85 mg/L, respectively), indicating that the wastewater discharge of the geothermal
power plant at Yangbajing has resulted in B, As, and F contamination in the river. Although the concentrations of B, As, and
F of the Zangbo river waters decline downstream of the wastewater discharge site due to dilution effect and sorption onto
bottom sediments, the sample from the conjunction of the Zangbo River and the Yangbajing River has higher contents of B, As,
and F as compared with their predicted values obtained using our regression analysis models. The differences between actual
and calculated contents of B, As, and F can be attributed to the contribution from upstream of the Yangbajing River. Water
quality deterioration of the river has induced health problems among dwellers living in and downstream of Yangbajing. Effective
measures, such as decontamination of wastewater and reinjection into the geothermal field, should be taken to protect the
environment at Yangbajing. 相似文献
25.
西北干旱区水中氟的分布规律及环境特征 总被引：20，自引：1，他引：19
西北干旱区天然水休事广泛分布以ＮａＦ和ＫＦ为主的氟特质。随干旱区内陆水系的产生、径流消亡,从山区至册前细土平原,Ｆ－的迁移分布具有显著的淋溶－径流 、径流－蒸发 与溶滤－蒸发浓缩富集３个水文化学分带;在白来者纱及第四系下更新统以来湖相沉积的湖盆洼地以及沙漠边缘地区,地下水中Ｆ－相对富集,且具有深部地下水Ｆ－含量大于浅层地下水及地表水的垂直分带性;Ｆ－的富集与贫化与水化学特征关系密切,一般情况下,低Ｓ 相似文献
26.
A systematic analysis of micas contained in effusive, pyroclastic and hypabyssal rocks of the Alban Hills Volcanic District (AHVD) (Central Italy) was made in order to characterise minerals of pyroclastic units for tephrostratigraphy and to obtain as much information as possible on the activity of volatiles in this magmatic system. The phlogopite shows a large range of F contents (between 0.50 and 7.50 wt%) that make it possible to discriminate different AHVD lithologies; in particular, micas of lava groundmass are characterised by extremely high F (up to 7.50 wt%) and Ba (up to 9.70 wt%) contents, seldom or never found in other magmatic ultrapotassic rocks. Moreover, the micas of pyroclastics, ultramafic cumulates and holocrystalline inclusions made up of leucite, clinopyroxene and phlogopite (hereafter italites) show Mg/(Mg+Fe) values between 0.65 and 0.90 that are not correlated with F contents. The variations in F contents observed in the AHVD micas do not appear to be due to a “temperature” effect or pressure changes, but they may be due to variations in the H2O and CO2 activities in the magma chamber. They make it possible to differentiate three crystallisation environments in the AHVD magmatic system. The first one had elevated CO2 activity and formed the italites near the carbonate contact; these rocks represent, at least those enriched in clinopyroxene without skarn-minerals, the hypabyssal crystallisation of the AHVD magmas at the periphery of magma chamber. The second one, characterised by a higher water activity, is represented by the micas of the ultramafic cumulates and pyroclastic scorias, and is located in the inner part of magma chamber. The third environment, the groundmass of the lavas, it is not related with the previous ones and is characterised by the absence of water and by a high F activity. In general, our results suggest that the compositional variations observed in the micas (Al, Si, Ti, Ba) reflect different H2O activities (inversely correlated with F activity) in the magma chamber. 相似文献
27.
茶园生态系统氟的生物地球化学循环 总被引：1，自引：0，他引：1
根据近年作者及相关研究成果,提出一般茶园（非F污染区,非高F地质背景区）生态系统F的生物地球化学循环模型,估算茶园生态系统各子系统F的库容和库之间的F流量,分析茶园生态系统F的生物地球化学特征．结果表明：1）茶园生态系统F的惰性库：调节库：活动库为239：4：1,活动库占总库容的比例高达0．41％,其比例是非常高的;2... 相似文献
28.
29.
N. V. Ramamohana Rao N. Rao K. Surya Prakash Rao R. D. Schuiling 《Environmental Geology》1993,21(1-2):84-89
Geochemical and hydrochemical studies were conducted in Nalgonda District (A.P.), to explore the causes of high fluorine in waters, causing a widespread incidence of fluorosis in the local population. Samples of granitic rocks, soils, stream sediments, and waters were analyzed for F and other salient chemical parameters. Samples from the area of Hyderabad city were analyzed for comparison. The F content of waters in areas with endemic fluorosis ranges from 0.4 to 20 mg/l. The low calcium content of rocks and soils, and the presence of high levels of sodium bicarbonate in soils and waters are important factors favoring high levels of F in waters. 相似文献
30.
东疆星星峡地区白石头泉高铷氟花岗岩的特征和成因 总被引：6，自引：4，他引：6
新疆哈密白石头泉高铷氟花岗岩体自中心往顶部可分为：淡色花岗岩、天河石花岗岩、黄玉天河石花岗岩和黄玉石英钠长岩等岩相。各岩相之间在矿物成分和结构构造上有着系统的变化。岩体的岩浆可能来自于挤压背景下富含泥质的地槽沉积物的超变质和部分熔融。其成岩作用包括了熔体中的直接结晶和岩浆晚期－期后热液的交代两个过程。高含量的氟对于岩浆的演化起着重要作用。 相似文献