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1.
Mantle xenoliths and xenocrysts from Guaniamo, Venezuela kimberlites record equilibration conditions corresponding to a limited range of sampling in the lithosphere (100-150 km). Within this small range, however, compositions vary considerably, but regularly, defining a strongly layered mantle sequence. Major and trace element compositions suggest the following lithologic sequence: highly depleted lherzolite from 100 to 115 km, mixed ultra-depleted harzburgite and lherzolite from 115 to 120 km, relatively fertile lherzolite from 120 to 135 km, and mixed depleted harzburgite and relatively fertile lherzolite from 135 to 150 km. Based on comparison with well-documented mantle peridotites and xenocrysts from elsewhere, we conclude that the Meso-proterozoic Cuchivero Province (host to the Guaniamo kimberlites) is underlain by depleted and ultra-depleted shallow Archean mantle that was underplated, and uplifted, by Proterozoic subduction, perhaps more than once. These Proterozoic subduction events introduced less-depleted oceanic lithosphere beneath the Archean section, which remains there and is the source of the abundant Guaniamo eclogite-suite diamonds that have ocean-floor geochemical signatures. Although diamond-indicative low-Ca Cr-pyrope garnets are abundant, they are derived primarily from the shallow depleted layer within the field of graphite stability, and the rare peridotite-suite diamonds are either metastably preserved at these shallow depths, or were derived from the small amount of depleted lithosphere sampled by these kimberlites that remains within the diamond stability field (the mixture of Archean and Proterozoic mantle in the depth range 135-150 km). 相似文献
2.
N. V. Sobolev F. V. Kaminsky W. L. Griffin E. S. Yefimova T. T. Win C. G. Ryan A. I. Botkunov 《Lithos》1997,39(3-4):135-157
The Sputnik kimberlite pipe is a small “satellite” of the larger Mir pipe in central Yakutia (Sakha), Russia. Study of 38 large diamonds (0.7-4.9 carats) showed that nine contain inclusions of the eclogitic paragenesis, while the remainder contain inclusions of the peridotitic paragenesis, or of uncertain paragenesis. The peridotitic inclusion suite comprises olivine, enstatite, Cr-diopside, chromite, Cr-pyrope garnet (both lherzolitic and harzburgitic), ilmenite, Ni-rich sulfide and a Ti-Cr-Fe-Mg-Sr-K phase of the lindsleyite-mathiasite (LIMA) series. The eclogitic inclusion suite comprises omphacite, garnet, Ni-poor sulfide, phlogopite and rutile. Peridotitic ilmenite inclusions have high Mg, Cr and Ni contents and high Nb/Zr ratios; they may be related to metasomatic ilmenites known from peridotite xenoliths in kimberlite. Eclogitic phlogopite is intergrown with omphacite, coexists with garnet, and has an unusually high TiO2 content. Comparison with inclusions in diamonds from Mir shows general similarities, but differences in details of trace-element patterns. Large compositional variations among inclusions of one phase (olivine, garnet, chromite) within single diamonds indicate that the chemical environment of diamond crystallisation changed rapidly relative to diamond growth rates in many cases. P-T conditions of formation were calculated from multiphase inclusions and from trace element geothermobarometry of single inclusions. The geotherm at the time of diamond formation was near a 35 mW/m2 conductive model; that is indistinguishable from the Paleozoic geotherm derived by studies of xenoliths and concentrate minerals from Mir. A range of Ni temperatures between garnet inclusions in single diamonds from both Mir and Sputnik suggests that many of the diamonds grew during thermal events affecting a relatively narrow depth range of the lithosphere, within the diamond stability field. The minor differences between inclusions in Mir and Sputnik may reflect lateral heterogeneity in the upper mantle. 相似文献
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F. Kaminsky O. Zakharchenko R. Davies W. Griffin G. Khachatryan-Blinova A. Shiryaev 《Contributions to Mineralogy and Petrology》2001,140(6):734-753
Alluvial diamonds from the Juina area in Mato Grosso, Brazil, have been characterized in terms of their morphology, syngenetic mineral inclusions, carbon isotopes and nitrogen contents. Morphologically, they are similar to other Brazilian diamonds, showing a strong predominance of rounded dodecahedral crystals. However, other characteristics of the Juina diamonds make them unique. The inclusion parageneses of Juina diamonds are dominated by ultra-high-pressure ("superdeep") phases that differ both from "traditional" syngenetic minerals associated with diamonds and, in detail, from most other superdeep assemblages. Ferropericlase is the dominant inclusion in the Juina diamonds. It coexists with ilmenite, Cr-Ti spinel, a phase with the major-element composition of olivine, and SiO2. CaSi-perovskite inclusions coexist with titanite (sphene), "olivine" and native Ni. MgSi-perovskite coexists with TAPP (tetragonal almandine-pyrope phase). Majoritic garnet occurs in one diamond, associated with CaTi-perovskite, Mn-ilmenite and an unidentified Si-Mg phase. Neither Cr-pyrope nor Mg-chromite was found as inclusions. The spinel inclusions are low in Cr and Mg, and high in Ti (Cr2O3<36.5 wt%, and TiO2>10 wt%). Most ilmenite inclusions have low MgO contents, and some have very high (up to 11.5 wt%) MnO contents. The rare "olivine" inclusions coexisting with ferropericlase have low Mg# (87-89), and higher Ca, Cr and Zn contents than typical diamond-inclusion olivines. They are interpreted as inverted from spinel-structured (Mg, Fe)2Si2O4. This suite of inclusions is consistent with derivation of most of the diamonds from depths near 670 km, and adds ilmenite and relatively low-Cr, high-Ti spinel to the known phases of the superdeep paragenesis. Diamonds from the Juina area are characterized by a narrow range of carbon isotopic composition ('13C=-7.8 to -2.5), except for the one majorite-bearing diamond ('13C=-11.4). There are high proportions of nitrogen-free and low-nitrogen diamonds, and the aggregated B center is predominant in nitrogen-containing diamonds. These observations have practical consequences for diamond exploration: Low-Mg olivine, low-Mg and high-Mn ilmenite, and low-Cr spinel should be included in the list of diamond indicator minerals, and the role of high-Cr, low-Ti spinel as the only spinel associated with diamond, and hence as a criterion of diamond grade in kimberlites, should be reconsidered. 相似文献
4.
Search and rescue (SAR) for both airborne and maritime vehicles has been an area of intense investigation for many years. Current techniques include employment of small distress transmitters which provide signals that have only a limited interception capability. This can considerably increase the search time and reduce its effectiveness. With the increased availability-existing and planned-of both synchronous and nonsynchronous satellites, SAR investigations are being directed toward the application of satellites. The present paper introduces the concept of satellite-based maritime search and rescue system (SAMSARS). This is a proposed pseudonoise (PN) wide-band spread spectrum system that would operate at low power levels and coexist with operational communication satellite systems (voice or data) without mutual interference. The use of existing operational satellite spectrum, instead of a dedicated distress channel or special satellites, is a major feature of SAMSARS. Other important aspects are its capability of providing unique identification and distress information in minutes following activation of the distress transmitter and its inherent immunity to false alarms. SAMSARS can also provide position location directly when three satellites are mutually visible or indirectly, by taking advantage of a vessel's on-board derived navigation data. This paper presents concept elements such as message structure, transmitter and receiver block diagrams, and unique features of SAMSARS. The paper also presents an operational example, including sample link power budgets, and finally specifies areas for further investigation. 相似文献
5.
Doklady Earth Sciences - The junction zone between Lomonosov submarine ridge and the shelf of the East Siberian Sea was studied. The aim was to prove the absence of a strike-slip fault in the... 相似文献
6.
E. A. Agafonov S. T. Kaminsky A. S. Kukushkin Yu. A. Prokhorenko 《Physical Oceanography》2000,10(4):351-364
On the basis of the results of simultaneous observations of parameters of currents, attenuation factor of light, and temperature
performed aboard a moving vessel, we established the main characteristics and features of the circulation of waters and the
structure of transparency and temperature fields in the surface layer of the northwest part of the Black Sea. We investigate
the correlation between the variability of fluid dynamics and redistribution of transparency and temperature fields. The measured
currents are compared with those calculated using the actual field of atmospheric pressure during the time of observation.
It is shown that the results obtained in the areas of steady currents in the west and central regions are in good agreement.
Translated by Peter V. Malyshev and Dmitry V. Malyshev 相似文献
7.
Kaminsky F. V. Shilobreeva S. N. Ber B. Ya. Kazantsev D. Yu. 《Doklady Earth Sciences》2020,494(1):699-703
Doklady Earth Sciences - The volumetric concentration of hydrogen in two Brazilian diamonds is determined using secondary ion mass spectrometry and implantation of hydrogen into an external... 相似文献
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9.
S. G. Boguslavsky L. A. Koveshnikov S. T. Kaminsky A. A. Markov 《Physical Oceanography》1992,3(5):357-365
Principal regularities of the coastal velocity field formation have been revealed on the basis of processing and analysis of multi-annual measurements of currents at a bold coast. The influence produced by the coastline, the wind force and its spatial-temporal variability, pycnocline, and the general circulation pattern on this field is estimated. The seiche and inertial currents in this region are characterized. Patterns of the transversal upwelling-downwelling circulations are developed for winter and summer.Translated by Mikhail M. Trufanov. 相似文献
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