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Research on the Upper Campanian (Upper Cretaceous) Negev phosphorites (Mishash Formation), based on microprobe analyses, Fourier Transform Infrared spectroscopy, wet chemistry, microtextural (Scanning Electron Microscopy) studies and mineralogical analyses, together with quantified rates of sedimentation and P accumulation, enables the chemistry of these rocks to be better constrained across the Negev area and allows their suitability for the manufacture of P fertilizers to be better determined. Two phosphorite facies are differentiated: (i) a pristine phosphorite facies of low P content, more typical of basinal sections and (ii) a reworked, granular phosphorite facies commonly enriched in P, found predominantly near palaeo‐highs and forming most of the economic phosphates. The distribution of F/P2O5, CO2/F, U(IV), Cd, Zn and other trace metals (Mo, Ni, Cr, Cu, V and Y), rare‐earth elements concentration, Ce and Eu anomalies and heavy rare earth elements enrichment, are controlled by these two facies. F/P2O5 in carbonate‐fluorapatite is much lower (0·090 to 0·107) in the pristine than in the reworked facies (0·107 to 0·120); in addition, the lower F/P2O5 in the pristine facies is coupled with: (i) higher Cd, Zn, Mo, Ni, Cr, Cu and V concentrations; (ii) a considerably reduced (< 10%) U(IV) fraction of total U; (iii) lower rare earth elements/P2O5 and Y/P2O5 ratios; (iv) less negative Ce and Eu anomalies and lower heavy rare earth elements (Lu/La) enrichment; (v) an increase in Fe‐rich smectites in the clay fraction; and (vi) presence of OH in the carbonate‐fluorapatite structure. Sedimentary reworking of previously formed pristine phosphate, together with its redeposition near structural highs in more oxic bottom conditions, results in considerable diagenetic changes in the chemistry of the phosphorites, making them more suitable for economic exploitation. The results presented here provide geochemical criteria for identifying pristine phosphate in other phosphorite sequences and may help to better locate phosphate strata chemically suitable for the phosphate industry elsewhere. 相似文献
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YAACOV NIR 《第四纪科学杂志》1997,12(2):143-151
During the course of a study of historical water wells along the Israeli shore, which has been in progress since 1984, an innovative method for investigating sea-level fluctuations was developed. Eighteen ancient water wells were re-dug, 14 by the author, and four by archaeologists. Most of the re-dug wells are found at archaeological sites located a very short distance inland from the present shoreline. Evidence of ancient ground-water levels found in the wells directly reflects on historic eustatic sea-level changes, and the rate at which the end of the post-glacial transgression advanced. A critical question concerns the durability and life span of these wells, as the true age is very important for the accurate reconstruction of a sea-level curve. The Pre-Pottery Neolithic well of Atlit-Yam, which is the oldest known well in the world (ca. 8000 yr old), enabled the most accurate sea-level reconstruction for early Holocene times. Sea-level rise during that period of the Atlit-Yam site was of the order of 20 mm yr−1 at the beginning, slowing to 6–8 mm yr−1 at the abandonment of this site at ca. 7.5 ka BP, when it was flooded by the advancing and rising sea. After reaching its present level, sea-level fluctuations for the past 2.5 millennia were not greater than 1.5 to 2 m. © 1997 John Wiley & Sons, Ltd. 相似文献
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Clinoptilolite, a zeolite of the heulandite group, occurs commonly in sediments as an authigenic mineral. In the Middle Eocene of southern Israel, it constitutes from a few per cent up to 80 per cent of the insoluble residue of the chalks and limestones. It is associated with opal C-T, montmorillonite and palygorskite. These chalks and limestones overlie the Danian-Palaeocene Taqiya marls which also contain a well-established clay mineral sequence consisting of opal C-T, montmorillonite, palygorskite, sepiolite, and clinoptilolite. This paragenesis of minerals is shown to be typical of the Upper Cretaceous to Eocene times. It is world-wide, occurs in deep-sea sediments as well as in shallow water sediments, and results from the abundance of silica which probably reflects a warmer climate during this time period. The concentration of magnesium in the sea-water and its ratio to the other cations seem to determine which authigenic silicate will be formed. 相似文献
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A. GALÁD P. PRAVEC P. KUŠNIRÁK Š. GAJDOŠ L. KORNOŠ J. VILÁGI 《Earth, Moon, and Planets》2005,97(1-2):147-163
The effort in photometry of near-Earth asteroids (NEAs) at Modra Observatory has been enhanced following a recent collaboration
with Ondřejov Observatory. We present a part of our collaborative work on measuring rotation lightcurve data for 10 NEAs.
We derived following synodic periods P and amplitudes of their composite lightcurves: (3553), 3.1944 h, 0.08 mag; (22753), 10.24 h, 0.11 mag; (31669), 5.807 h,
0.07–0.27 mag; (40267), 4.9568 h, 1.01–1.11 mag; (66146), 2.3774 h, 0.12–0.15 mag; (88188), 2.6906 h, 0.06 mag; (103067),
9.489 h, 0.49 mag; 2001 CB21, 3.302 h, 0.19 mag; 2004 LJ1, 2.7247 h, 0.17–0.59 mag; 2004 XO14, 8.417 h, 0.19–0.25 mag. While the derived periods are unique (the reliability code U=3) for most of the objects, those of (3553), (22753) and 2001 CB21 are somewhat less reliable (U=2). We checked all the U=3 data for deviations from strict periodicity, but found no significant attenuation that would indicate the presence of a
satellite. Absolute magnitudes in Cousins R band (H
R
) were derived for (3553), 16.05; (40267), 15.59; (88188), 16.04; 2004 XO14, 15.84; errors of the first three H
R
estimates are 0.20 mag, but that of 2004 XO14 is <0.10 mag. 相似文献
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For a petroleum geologist knowledge of the density of the distribution of subsurface Cretaceous reefs is a matter of practical interest. Hence, the discovery in the Judean Desert of Israel, near the western margin of the Dead Sea, of an exhumed sea bottom below an erosional unconformity is of particular interest, because it reveals the original distribution of such reefs, and thus may provide a clue to their subsurface distribution. In this desert, newly described Turonian (Upper Cretaceous) reefs are the dominant geomorphic features, as in their original habitat on the Cretaceous sea bottom. These reefs can be traced on aerial photographs: they are generally 5-15 m in diameter and 1-2.5 m in vertical dimension. Generally, reefs occur within 100-200 m of one another; in many places they are less than 50 m apart. The shapes of the patch or pinnacle reefs are almost circular, as are those occurring in the Edwards Limestone (Comanchean, Lower Cretaceous) in central Texas (Roberson, 1972). The hard, resistant, ring-like outer rims of these exposed reefs weather out as raised rims. A central depression within such structures consists, in places, of Senonian soft chalky or friable material that has been interpreted as a diagenetic product of the vadose zone. The massive reef core consists of porous dolomite. The flanking strata which dip away from the reef core at angles of approximately 15-25° are composed of a probable original grainstone which has been diagenetically changed to a micritic fabric. 相似文献
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