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Reactive surface area is one of the key parameters for studying the kinetics of mineral dissolution. The common practice in experimental kinetics is to normalize the dissolution rate to the surface area measured by the BET method. The relationship between BET surface area and the reactive surface area is not trivial in minerals such as smectites, which possess both internal and external surface areas, and in which the dissolution is controlled by the chemical attack on the edge surface. The present study examines two proxies for the reactive surface area of the Clay Mineral Society reference smectite SAz-1: BET surface area and the edge surface area measured using AFM.Since smectites are very microporous, their BET surface area is strongly influenced by the degassing procedure. It is demonstrated that outgassing the smectite powder at 135°C in a 15 mL min−1 N2 gas flow for at least 24 hours minimizes contribution from micropores to less than 11% of the BET surface area.Following dissolution experiments in solutions with a low electrolyte concentration, the BET surface area increased from 34 ± 2 m2 g−1 in raw SAz-1 to 127 ± 13 m2 g−1 in SAz-1 sample recovered from dissolution experiments. This increase in BET surface area is explained by a decrease in the average size of the smectite aggregates, and by an increase in microporosity due to the depletion in the major interlayer cation, i.e., Ca2+. As the BET surface area of the raw smectite sample includes considerably less microporosity compared to the BET surface area of the smectite recovered from dissolution experiments, the former is a better approximation of the external surface area of the dried sample powder.AFM measurements show that there is no correlation between the specific external surface area of the sample and its specific edge surface area. This observation is explained by the platy morphology of the smectite particle in which the specific external surface area depends linearly on the height reciprocal, whereas the specific edge surface area is independent of the particles height and depends linearly on the sum of the reciprocals of the length of the axes. Therefore, there is no reason to expect a correlation between the BET and the edge surface area. Our results show that the edge surface area (4.9 ± 0.7 m2 g−1) of the smectite particles cannot be predicted based on its external surface area (136 ± 20 m2 g−1). Therefore, the BET surface area cannot serve as a proxy for the reactive surface area. We suggest using AFM measurements of the specific edge surface area as an alternative proxy for the reactive surface area of smectite. 相似文献
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Rachelle B. Turnier Yaron Katzir Kouki Kitajima Ian J. Orland Michael J. Spicuzza John W. Valley 《Journal of Metamorphic Geology》2020,38(1):53-70
Corundum (Crn), including sapphire, occurs in emery pods surrounded by marble on the island of Naxos, Greece. The emery formed from bauxite deposited in karst that was metamorphosed to 400–700°C at 20–15 Ma. Many of these rocks initially appeared well suited for refractory accessory mineral (RAM) thermometry, which uses oxygen isotope fractionation between a RAM – corundum – and a modally dominant phase with faster diffusion of oxygen – calcite (Cc) – to determine peak metamorphic temperatures. However, previous attempts at oxygen isotope thermometry were confounded by highly variable fractionations (Δ18O) measured at mm-scale and the uncertain calibration of Δ18O(Cc-Crn) versus temperature. Secondary ion mass spectrometry (SIMS) permits in situ analysis of δ18O in corundum and calcite at the 10-μm scale in adjacent grains where textures suggest peak metamorphic equilibrium was attained. SIMS analyses of adjacent mineral pairs in eight rocks yield values of Δ(Cc-Crn) that systematically decrease from 7.2 to 2.9‰ at higher metamorphic grade. Pairing these data with independent temperature estimates from mineral isograds yields an empirical calibration of 1,000 lnα(Cc-Crn) = 2.72 ± 0.3 × 106/T2 (T in K). The new fractionations (2.7‰ at 1,000 K) are significantly smaller than those calculated from the modified increment method (6.5‰ at 1,000 K; Zheng, Geochimica et Cosmochimica Acta, 1991, 55:2299–2307; Zheng, Mineral Mag, 1994, 58A:1000–1001), which yield unreasonably high temperatures of 630 to 1,140°C when applied to the new Naxos data. The new calibration of Δ(Cc-Crn) can be combined with published fractionations to calculate A-factors for corundum versus a range of 14 other minerals. These new fractionation factors can be used for thermometry or to constrain the genesis of corundum. A compilation of gem corundum δ18O values shows that many igneous sapphires, including important deposits of basalt-associated sapphire, are mildly elevated in δ18O relative to the calculated range in equilibrium with mantle values (4.4–5.7‰) and formed from evolved magmas. 相似文献
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Raanan Katzir 《中国沙漠》2000,20(2):113-117
以色列的沙漠地区占土总面积的６％,沙漠地区的传统农业是以大面积的牧场上放牧少量耐旱畜种以及种植少量抗时粮食作物为基础的;沙漠地区的现代化农业是依靠外来水源,如从加利利海引来的水和人口密集的中心城市的再循环污水为基础的。有些地区的咸水可用于灌溉耐盐作物,如马玲薯、瓜类、葡萄、橄榄和枣树,有些作物还可采用滴灌法。严酷的沙漠气候条件可采用温室加以控制,主要生产供出口的淡季疏散、花卉和香草。在海滨地区的浙 相似文献
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Yaron Katzir John W. Valley Alan Matthews Michael J. Spicuzza 《Contributions to Mineralogy and Petrology》2002,142(6):700-713
Horizons of ultramafic lenses were metamorphosed with host felsic gneisses at upper amphibolite facies conditions during the M2 event on the island of Naxos, Greece. The synkinematic peak M2 Ol-Opx-Hbl-Chl-Spl assemblage of the Main, migmatite-associated, Ultramafic Horizon (MUH) retains mantle-like chemical and oxygen isotope compositions and thus shows no evidence of infiltration of fluids from the host rocks. A bimodal distribution of temperatures, grouped at 700 and 1,200 °C, is given by oxygen isotope Opx-Ol thermometry in the MUH meta-peridotites and indicates partial oxygen exchange during M2 superposed over previous mantle fractionation. The Agia Ultramafic Horizon (AUH), a coarser-grained and unfoliated peridotite, occurs within sillimanite gneisses in northwest Naxos and contains talc-enstatite and olivine domains. Recrystallization of the AUH peridotite during post-peak M2 infiltration of silica-rich, high '18O fluids is indicated by lack of deformation, increased activity of silica required to stabilize the talc-enstatite assemblage, extremely high '18O values of Ol and Opx and (18O(Opx-Ol) temperatures of 520-650 °C. The source for these fluids is inferred to be aplitic and pegmatitic dikes emanating from the migmatitic core of Naxos and intruding the AUH. At peak M2 temperatures and during anatexis of gneisses, volumes of fluid were small and fluid composition was locally buffered in the deeper part of the Naxos section. Crystallization of melts within the migmatitic core released siliceous fluids and initiated an episode of retrograde hydrous metamorphism in the overlying sequences, as observed in the AUH. 相似文献
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Y. Katzir M. Eyal B.A. Litvinovsky B.M. Jahn A.N. Zanvilevich J.W. Valley Y. Beeri I. Pelly E. Shimshilashvili 《Lithos》2007,95(3-4):208-228
The central pluton within the Neoproterozoic Katharina Ring Complex (area of Gebel Mussa, traditionally believed to be the biblical Mt. Sinai) shows a vertical compositional zoning: syenogranite makes up the bulk of the pluton and grades upwards to alkali-feldspar granites. The latters form two horizontal subzones, an albite–alkali feldspar (Ab–Afs) granite and an uppermost perthite granite. These two varieties are chemically indistinguishable. Syenogranite, as compared with alkali-feldspar granites, is richer in Ca, Sr, K, Ba and contains less SiO2, Rb, Y, Nb and U; Eu/Eu* values are 0.22–0.33 for syenogranite and 0.08–0.02 for alkali-feldspar granites. The δ18O (Qtz) is rather homogeneous throughout the pluton, 8.03–8.55‰. The δ18O (Afs) values in the syenogranite are appreciably lower relative to those in the alkali–feldspar granites: 7.59–8.75‰ vs. 8.31–9.12‰. A Rb–Sr isochron (n = 9) yields an age of 593 ± 16 Ma for the Katharina Ring Complex (granite pluton and ring dikes).
The alkali–feldspar granites were generated mainly by fractional crystallization of syenogranite magma. The model for residual melt extraction and accumulation is based on the estimated extent of crystallization ( 50 wt.%), which approximates the rigid percolation threshold for silicic melts. The fluid-rich residual melt could be separated efficiently by its upward flow through the rigid clusters of crystal phase. Crystallization of the evolved melt started with formation of hypersolvus granite immediately under the roof. Fluid influx from the inner part of the pluton to its apical zone persisted and caused increase of PH2O in the magma below the perthite granite zone. Owing to the presence of F and Ca in the melt, PH2O of only slightly more than 1 kbar allows crystallization of subsolvus Ab–Afs granite. Abundance of turbid alkali feldspars and their 18O/16O enrichment suggest that crystallization of alkali-feldspar granites was followed by subsolvus fluid–rock interaction; the δ18O (Fsp) values point to magmatic origin of fluids.
The stable and radiogenic isotope data [δ18O (Zrn) = 5.82 ± 0.06‰, ISr = 0.7022 ± 0.0064, εNd (T) values are + 3.6 and + 3.9] indicate that the granite magma was generated from a ‘juvenile’ source, which is typical of the rocks making up most of the Arabian–Nubian shield. 相似文献
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The Variscan orogenesis in Europe peaked during the Late Devonian–Early Carboniferous times when Gondwanan terranes collided with Laurasia. Hitherto it has been thought that Carboniferous tectonics in northern Arabia and the adjacent parts of NE Africa were broad swells (‘arches’) and depressions (‘basins’) that formed as a far-field contractional effect of the Variscan compression. The discovery of a 351 ± 3 Ma (U–Pb in zircon) within-plate felsic volcanism in the Helez borehole, southern coastal Israel, suggests that the Levant Arch is, instead, extensional in origin. Felsic volcanism was associated with gabbro underplating of the crust, an extreme (~50°C/km) crustal thermal gradient, major uplift, and truncation of the ≥2.5 km section. Taken together with the recent discovery of the ~340 Ma oceanic crust in the Eastern Mediterranean, the Levant Arch is interpreted as an uplifted shoulder of a rift, preceding ocean spreading. 相似文献
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Raanan Katzir 《寒旱区科学》2015,7(1):0001-0006
The Israeli Desert constitutes 60% of the country's total area. Regional annual precipitation is 100–200 mm and evaporation reaches 2,500 mm. Traditional desert agriculture of rain fed wheat and sheep, goat and camels grazing is common. Despite the harsh climate conditions, advance agriculture is concentrated in foci where water resources exist. Desert agriculture takes advantage of the winter(October–April) due to a mild climate season for growing vegetables, flowers, herbs and fruit which are mostly exported to European countries. The key factor is the sustainable management of the local natural resources. The regional research and development(RD) system is generating adequate local knowledge and technologies. The most important key factor is developing water resources, and using irrigation saving water systems such as drip irrigation. Technologies of protected agriculture such as greenhouses and plastic tunnels are used. The unfit desert soil is substitute by sand and artificial growing media. For gaining market purposes, introduction of botanical species was implemented for various flowers and vegetable varieties, avocado, pitaya, and jojoba. Controlled drip irrigation and drainage helps to solve salinity problems. Integrated Pest Management(IPM) is used to overcome plant protection issues. Advance raising of milking cows was developed by using reduction heat stress methods. Tilapia are raised in open ponds and greenhouse ponds, and ostriches adapted to desert conditions were introduced. On the southern Judean hills where precipitation is 250 mm, through soil conservation and rain harvesting, significant afforestation is changing the desert scenery. The human factor on this process such as farmers, agricultural extension agents and research scientists is the leading factor. 相似文献
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Interval velocity analysis using post‐stack data has always been a desire, mainly for 3D data sets. In this study we present a method that uses the unique characteristics of migrated diffractions to enable interval velocity analysis from three‐dimensional zero‐offset time data. The idea is to perform a standard three‐dimensional prestack depth migration on stack cubes and generate three‐dimensional common image gathers that show great sensitivity to velocity errors. An efficient ‘top‐down’ scheme for updating the velocity is used to build the model. The effectiveness of the method is related to the incorporation of wave equation based post‐stack datuming in the model building process. The proposed method relies on the ability to identify diffractions along redatumed zero‐offset data and to analyse their flatness in the migrated local angle domain. The method can be considered as an additional tool for a complete, prestack depth migration based interval velocity analysis. 相似文献
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Bar Elisha Yaron Katzir Andrew R. C. Kylander‐Clark Tzahi Golan Matthew A. Coble 《Journal of Metamorphic Geology》2019,37(5):591-610
Collision‐related granitoid batholiths, like those of the Hercynian and Himalayan orogens, are mostly fed by magma derived from metasedimentary sources. However, in the late Neoproterozoic calcalkaline (CA) batholiths of the Arabian–Nubian Shield (ANS), which constitutes the northern half of the East African orogen, any sedimentary contribution is obscured by the juvenile character of the crust and the scarcity of migmatites. Here, we use paired in situ LASS‐ICP‐MS measurements of U–Th–Pb isotope ratios and REE contents of monazite and xenotime and SHRIMP‐RG analyses of separated zircon to demonstrate direct linkage between migmatites and granites in the northernmost ANS. Our results indicate a single prolonged period of monazite growth at 640–600 Ma, in metapelites, migmatites and peraluminous granites of three metamorphic suites: Abu‐Barqa (SW Jordan), Roded (S Israel) and Taba–Nuweiba (Sinai, Egypt). The distribution of monazite dates and age zoning in single monazite grains in migmatites suggest that peak thermal conditions, involving partial melting, prevailed for c. 10 Ma, from 620 to 610 Ma. REE abundances in monazite are well correlated with age, recording garnet growth and garnet breakdown in association with the prograde and retrograde stages of the melting reactions, respectively. Xenotime dates cluster at 600–580 Ma, recording retrogression to greenschist facies conditions as garnet continued to destabilize. Phase equilibrium modelling and mineral thermobarometry yield P–T conditions of ~650–680°C and 5–7 kbar, consistent with either water‐fluxed or muscovite‐breakdown melting. The expected melt production is 8–10 vol.%, allowing a melt connectivity network to form leading to melt segregation and extraction. U–Pb ages of zircon rims from leucosomes indicate crystallization of melt at 610 ± 10 Ma, coinciding with the emplacement of a vast volume of CA granites throughout the northern ANS, which were previously considered post‐collisional. Similar monazite ages (c. 620 Ma) retrieved from the amphibolite facies Elat schist indicate that migmatites are the result of widespread regional rather than local contact metamorphism, representing the climax of the East African orogenesis. 相似文献