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The results of SEST millimeter observations of the molecular cloud G345.01+1.79 are presented. Spectra of CH3OH, SO2, SiO, HCO+, C18O, C33S, C34S, HCN, and DCN lines have been obtained. Mapping of the cloud in CH3OH, SiO, and C34S lines indicates that the maximum integrated intensity in the SiO and C34S lines and in low-excitation CH3OH transitions coincide with the northern group of methanol masers, while the corresponding maximum for high-excitation CH3OH transitions coincides with the southern methanol-maser group. The physical parameters are estimated from the quasi-thermal CH3OH lines under the large-velocity-gradient approximation, and their distribution on the sky derived. The density and temperature are higher toward the southern group of methanol masers than in the northern group. This may indicate that star formation is in an earlier stage of evolution in the northern than toward the southern group. A maser component can be distinguished in 14 (of 71) CH3OH lines. We have detected for the first time weak, probably maser, emission in the CH3OH lines at 148.11, 231.28, 165.05, 165.06, and 165.07 GHz. A blue wing is clearly visible in the CH3OH, SiO, C18O, and SO2 lines. The emission in this wing is probably associated with a compact source whose velocity is characteristic of the CH3OH maser emission in the southern group of masers. 相似文献
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Nikolay Bonev Jean-Pierre Burg Zivko Ivanov 《International Journal of Earth Sciences》2006,95(2):318-340
The tectonic evolution of the Rhodope massif involves Mid-Cretaceous contractional deformation and protracted Oligocene and Miocene extension. We present structural, kinematic and strain data on the Kesebir–Kardamos dome in eastern Rhodope, which document early Tertiary extension. The dome consists of three superposed crustal units bounded by a low-angle NNE-dipping detachment on its northern flank in Bulgaria. The detachment separates footwall gneiss and migmatite in a lower unit from intermediate metamorphic and overlying upper sedimentary units in the hanging wall. The high-grade metamorphic rocks of the footwall have recorded isothermal decompression. Direct juxtaposition of the sedimentary unit onto footwall rocks is due to local extensional omission of the intermediate unit. Structural analysis and deformational/metamorphic relationships give evidence for several events. The earliest event corresponds to top-to-the SSE ductile shearing within the intermediate unit, interpreted as reflecting Mid-Late Cretaceous crustal thickening and nappe stacking. Late Cretaceous–Palaeocene/Eocene late-tectonic to post-tectonic granitoids that intruded into the intermediate unit between 70 and 53 Ma constrain at least pre-latest Late Cretaceous age for the crustal-stacking event. Subsequent extension-related deformation caused pervasive mylonitisation of the footwall, with top-to-the NNE ductile, then brittle shear. Ductile flow was dominated by non-coaxial deformation, indicated by quartz c-axis fabrics, but was nearly coaxial in the dome core. Latest events relate to brittle faulting that accommodated extension at shallow crustal levels on high-angle normal faults and additional movement along strike-slip faults. Radiometric and stratigraphic constraints bracket the ductile, then brittle, extensional events at the Kesebir–Kardamos dome between 55 and 35 Ma. Extension began in Paleocene–early Eocene time and displacement on the detachment led to unroofing of the intermediate unit, which supplied material for the syn-detachment deposits in supra-detachment basin. Subsequent cooling and exhumation of the footwall unit from beneath the detachment occurred between 42 and 37 Ma as indicated by mica cooling ages in footwall rocks, and extension proceeded at brittle levels with high-angle faulting constrained at 35 Ma by the age of hydrothermal adularia crystallized in open spaces created along the faults. This was followed by Late Eocene–Oligocene post-detachment overlap successions and volcanic activity. Crustal extension described herein is contemporaneous with the closure of the Vardar Ocean to the southwest. It has accommodated an earlier hinterland-directed unroofing of the Rhodope nappe complex, and may be pre-cursor of, and/or make a transition to the Aegean back-arc extension that further contributed to its exhumation during the Late Miocene. This study underlines the importance of crustal extension at the scale of the Rhodope massif, in particular, in the eastern Rhodope region, as it recognizes an early Tertiary extension that should be considered in future tectonic models of the Rhodope and north Aegean regions. 相似文献
109.
G. A. Sobolev A. V. Ponomarev A. V. Koltsov V. B. Smirnov 《Pure and Applied Geophysics》1996,147(2):345-355
The experiments were conducted for the study of stick-slip at the contact between two granite blocks. Three cases were studied under the following conditions: 1) the increase of load at a constant rate; 2) the additional application of sinusoidal oscillations in the frequency range from 1 to 30 Hz; 3) subjection to the impulse in the kilohertz frequency range. The imposition of sinusoidal oscillations with the amplitude of 15% of the maximal load caused the reduction of time by 10% for the discussed in terms of durability. The high frequency impulse influence increased this effect and also caused essential changes in the amplitude of elastic oscillations generating during the stick-slip. The trigger phenomena should be integrated in prediction models of the time and magnitude of earthquakes. 相似文献
110.
B. L. Beard Kathy N. Fraracci Robert A. Clayton Toshiko K. Mayeda G. A. Snyder N. V. Sobolev L. A. Taylor 《Contributions to Mineralogy and Petrology》1996,125(4):293-310
Diamond-bearing eclogites are an important component of the xenoliths that occur in the Mir kimberlite, Siberian platform,
Russia. We have studied 16 of these eclogite xenoliths, which are characterized by coarse-grained, equigranular garnet and
omphacite. On the basis of compositional variations in garnet and clinopyroxene, this suite of eclogites can be divided into
at least two groups: a high-Ca group and a low-Ca group. The high-Ca group consists of high-Ca garnets in equilibrium with
pyroxenes that have high Ca-ratios [Ca/(Ca+Fe+Mg)] and high jadeite contents. These high-Ca group samples have high modal%
garnet, and garnet grains often are zoned. Garnet patches along rims and along amphibole- and phlogopite-filled veins have
higher Mg and lower Ca contents compared to homogeneous cores. The low-Ca group consists of eclogites with low-Ca garnets
in equilibrium with pyroxenes with a low Ca-ratio, but variable jadeite contents. These low-Ca group samples typically have
low modal% of garnet, and garnets are rarely compositionally zoned. Three samples have mineralogic compositions and modes
transitional to the high- and low-Ca groups. We have arbitrarily designated these samples as the intermediate-Ca group. The
rare-earth-element (REE) contents of garnet and clinopyroxene have been determined by ion microprobe. Garnets from the low-Ca
group have low LREE contents and typically have [Dy/Yb]n < 1. The high-Ca group garnets have higher LREE contents and typically have [Dy/Yb]n > 1. Garnets from the intermediate-Ca group have REE contents between the high- and low-Ca groups. Clinopyroxenes from the
low-Ca group have convex-upward REE patterns with relatively high REE contents (ten times chondrite), whereas those from the
high-Ca group have similar convex-upward shapes, but lower REE contents, approximately chondritic. Reconstructed bulk-rock
REE patterns for the low-Ca group eclogites are relatively flat at approximately ten times chondrite. In contrast, the high-Ca
group samples typically have LREE-depleted patterns and lower REE contents. The δ18O values measured for garnet separates range from 7.2 to 3.1‰. Although there is a broad overlap of δ18O between the low-Ca and high-Ca groups, the low-Ca group samples range from mantle-like to high δ18O values (4.9 to 7.2‰), and the high-Ca group garnets range from mantle-like to low δ18O values (5.3 to 3.1‰). The oxygen isotopic compositions of two of the five high-Ca group samples and four of the eight low-Ca
group eclogites are consistent with seawater alteration of basaltic crust, with the low-Ca group eclogites representative
of low-temperature alteration, and the high-Ca group samples representative of high-temperature hydrothermal seawater alteration.
We interpret the differences between the low- and high-Ca group samples to be primarily a result of differences in the protoliths
of these samples. The high-Ca group eclogites are interpreted to have protoliths similar to the mid to lower sections of an
ophiolite complex. This section of oceanic crust would be dominated by rocks which have a significant cumulate component and
would have experienced high-temperature seawater alteration. Such cumulate rocks probably would be LREE-depleted, and can
be Ca-rich because of plagioclase or clinopyroxene accumulation. The protoliths of the low-Ca group eclogites are interpreted
to be the upper section of an ophiolite complex. This section of oceanic crust would consist mainly of extrusive basalts that
would have been altered by seawater at low temperatures. These basaltic lavas would probably have relatively flat REE patterns,
as seen for the low-Ca group eclogites.
Received: 10 July 1995 / Accepted: 17 May 1996 相似文献