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The Al–Mg-rich granulites from the In Ouzzal craton, Algeria, show a great diversity of mineral reactions which correspond to continuous equilibria as predicted by phase relationships in the FeO–MgO–Al2O3–SiO2 system. The sequence of mineral reactions can be subdivided into three distinct stages: (1) a high-P stage characterized by the growth of coarse mineral assemblages involving sapphirine and the disappearance of early corundum and spinel-bearing assemblages; (2) a high-T stage characterized by the development of Sa–Qz-bearing assemblages; and (3) a later stage, in which garnet-bearing assemblages are replaced by more or less fine symplectites involving cordierite. During the course of early mineral reactions, the distribution coefficient, Kd, between the various ferromagnesian phases decreased significantly whereas Al2O3 in pyroxene increased concomitantly. These observations, when combined with topological constraints, clearly indicate that the high-P stage 1 was accompanied by a significant rise in temperature (estimated at 150 ± 50° C) under near isobaric conditions, in agreement with the reaction textures. By stage 2, pressure and temperature were extreme as evidenced by the low Kd value between orthopyroxene and garnet (Kd= 2.06–1.99), the high alumina content in pyroxene (up to 11.8%) and the high magnesium content in garnet [100 Mg/(Mg + Fe) = 60.6]. Mineral thermometry based on Fe–Mg exchange between garnet and pyroxene and on Al-solubility in pyroxene gives temperatures close to 970 ± 70° C at 10 ± 1.5 kbar. These results are in agreement with the development of Sa–Qz assemblages on a local scale. Late mineral reactions have been produced during a decompression stage from about 9 to 6 kbar. Except for local re-equilibration of Mg and Fe at grain boundaries, there is no evidence for further reactions below 700° C. We interpreted the whole set of mineral reactions as due to changes in pressure and temperature during a tectonic episode located at c. 2 Ga. Because of the lack of evidence for further uplift after the thermal relaxation which occurred at c. 6 kbar, it is possible however that the exhumation of this granulitic terrane occurred in a later tectonic event unrelated to its formation. 相似文献
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H. M. Tovmassian R. Kh. Hovhanessian R. A. Epremian D. Huguenin S. I. Serova V. G. Titov M. KH. Manarov 《Astrophysics and Space Science》1990,174(2):297-302
The results of UV-observations at 1640 Å of the regions of stellar associations Per OB1, Sco OB1, and Cyg OB1 made with the space telescope Glazar are presented. Respectively, 42, 22, and 30 hot stars brighter than 10m at 1640 Å were detected and measured in the mentioned stellar associations. A few of them are suspected to be variable in far UV. 相似文献
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介绍了如何将互联网技术应用于石油行业的局域网或广域网中,在服务器端提供图形信息数据库的服务,并在客户端利用浏览器进行图形信息的查询,实现勘探开发图形信息的共享。 相似文献
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吉林南部辉南-靖宇地区岩石圈地幔氧化-还原状态及研究意义 总被引:3,自引:2,他引:1
吉林省南部辉南-靖宇地区第四纪碱性玄武岩中的地幔包体主要为尖晶石相二辉橄榄岩和方辉橄榄岩。二辉橄榄岩和方辉橄榄岩的平衡温度分别为770~1000℃和850~1025℃,对应的氧逸度 (fO2)值分别为FMQ -0.70至+0.34 (均值为FMQ -0.06) 和FMQ -0.46至+0.05 (均值为FMQ -0.15),它们与深海橄榄岩(abyssal peridotites)以及软流圈地幔的fO2相似。橄榄岩的fO2值,连同其全岩化学成分(如Mg#、Al2O3、CaO、Ni、Co和Cr)和矿物化学成分(如橄榄石的Fo、尖晶石的Cr#和Mg#,以及辉石的Mg#)特征,表明辉南-靖宇地区龙岗火山群下面的岩石圈地幔很可能是在晚中生代以来,伴随着华北克拉通和扬子板块的碰撞以及来自东侧太平洋板块和北侧蒙古-额霍次克(Mongolo-Okhotsk)板块分别向西和向南的俯冲叠加,原来的古老岩石圈失衡、塌陷(拆沉?),取而代之的深部软流圈底辟、上涌,又经历了低度部分熔融的产物。 相似文献
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V.S. Tsypin D.KH. Morozov J.J.E. Herrera J.J. Martinell M. Tendler I.F. Potapenko A.S. de Assis C.A. de Azevedo 《Astrophysics and Space Science》1997,256(1-2):431-436
The transport processes in edge (collisional) plasmas of tokamaks with smooth profiles of macroscopic plasma parameters and induced poloidal and toroidal plasma flows, are considered. The toroidal and poloidal velocities of particles, the radial electric field and the ion heat flux are derived. It is shown that forces, induced by radio frequency waves, plasma turbulence or neutral beam injection, can be used to control the poloidal and toroidal plasma velocities, as well as ion heat conductivity, in a wide range of these values. 相似文献
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Assessing changes in nutrient status in the Richmond River estuary,Australia, using paleolimnological methods 总被引:1,自引:0,他引:1
Brendan Logan Kathryn H. Taffs Bradley D. Eyre Atun Zawadski 《Journal of Paleolimnology》2011,46(4):597-611
Eutrophication from nutrient over-enrichment is a serious problem for the coastal zone and the estuarine environment globally.
Australian estuaries are generally oligotrophic, but assessing whether they are becoming more eutrophic over time is inhibited
by a lack of long-term monitoring data. The Richmond River, Australia, provided an ideal example of an estuary under anthropogenic
pressure where the use of paleoecological techniques may potentially be used to reconstruct changes in nutrient status over
time. Five cores were extracted from depositional areas in the Richmond River, and subjected to paleo-magnetic profiling and
loss-on-ignition testing to ensure the core of greatest integrity was selected for further analytical work. Results from diatom
and stable isotope analyses combined with 210Pb and AMS 14C dating show a strong indication that the total phosphorus levels in the Richmond River have fluctuated since 1940. Evidence
also suggests that these fluctuations are most likely a function of climate. This study has successfully applied paleolimnological
techniques to the estuarine environment to produce information that can be used by environmental managers to aid decision
making in relation to nutrient control for the Richmond River. Further work using paleolimnological techniques should be aimed
at the extraction of a core containing diatoms that pre-date European settlement and include analyses of specific lipids and
fatty acid biomarkers. 相似文献