排序方式: 共有28条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
The Sanandaj-Sirjan zone of Iran is a metamorphic belt consisting of rocks which were metamorphosed under different pressure and temperature conditions and intruded by various plutons ranging in composition from gabbro to granite. The majority of these granitoids formed along the ancient active continental margin of the Neo-Tethyan ocean at the southeastern edge of the central Iranian microplate. Geochronological data published in recent years indicate periodic plutonism lasting from Carboniferous through Mesozoic to late-Paleogene times (from ca. 300 to ca. 35 Ma) with climax activity during the mid- and late-Jurassic. The age constraints for plutonic complexes, such as Siah-Kouh, Kolah-Ghazi, Golpayegan (Muteh), Azna, Aligoodarz, Astaneh, Borujerd, Malayer (Samen), Alvand, Almogholagh, Ghorveh, Saqqez, Marivan, Naqadeh and Urumieh, clearly indicate the periodic nature of magmatism. Therefore, the Sanandaj-Sirjan zone preserves the record of magmatic activity of a complete orogenic cycle related to (1) Permocarboniferous(?) rifting of Gondwana and opening of the Neo-Tethyan ocean, (2) subduction of the oceanic crust, (3) continental collision and (4) post-collision/post-orogenic activities. The formation of the Marivan granitoids, northwestern Sanandaj-Sirjan zone, for which we present U-Pb zircon and titanite ages of ca. 38 Ma, can be related to the collisional and post-collisional stages of this orogenic cycle. 相似文献
5.
6.
Deep geopolitical changes in the South Caucasus have considerably influenced the relationships of Iran and the three republics of Armenia, Azerbaijan and Georgia. Geographical location and strategic significance have made this region one of the most important in the world. Because of its historical affinities and socio-cultural links with the region's peoples, the Islamic Republic of Iran has expanded political-economic cooperation with them. The active presence of regional and trans-regional actors has directly affected this relation. This article mainly seeks to examine Iran's relations with the South Caucasus republics, considering the opportunities created since their independence following the collapse of the Soviet Union. 相似文献
7.
Urban air pollution is a major health risk in several large Iranian cities. Transportation, extensive use of fossil fuels, outdated urban fleets of gasoline and diesel vehicles, industrial sources within and close to the city boundaries and natural dust are major contributing factors. Starting with Tehran, emission inventories and mathematical air pollution models are being developed. Air quality is being monitored and reported to the public, though data availability and validity remain a challenge. While national and local air pollution mitigation plans are in place, progress remains slow, coordination is weak, and sources of funding are limited. 相似文献
8.
Amir Hossein Rahiminejad Mehdi Yazdi Ali Reza Ashouri 《Alcheringa: An Australasian Journal of Paleontology》2013,37(4):571-592
Colonial scleractinian corals were sampled from three levels within a Miocene marine unit of the Bakhtiari succession, Zagros Basin, central-western Iran. The first two coral-bearing intervals, A and B, contain small-scale scattered colonies and show a poor coral diversity, whereas the third, consisting of a strongly lithified limestone package, reflects a well-developed biostromal framework with higher coral skeletal volume within the Bakhtiari succession. The Bakhtiari succession coral assemblages are characterized by Porites sp. cf. P. maigensis, Porites sp. cf. P. mancietensis, Porites sp. cf. P. collegniana, Tarbellastraea reussiana, Favia sp., Montastrea sp. cf. P. tchihatcheffi, Favites sp. cf. P. neugeboreni, Favites sp. cf. P. neuvillei, Agathiphyllia sp. and Acropora sp. Sedimentological and palaeontological data indicate that the depositional environment is consistent with a mixed carbonate–siliciclastic ramp that was gently deepening basinwards from the shoreline. The hemispherical and massive growth forms of colonies and sparse branching forms dominated the well-illuminated euphotic zone. Abundant domestone and dense pillarstone coral growth fabrics interdigitating with coarse-grained terrigenous sediments developed in the shallow inner ramp environment. Branching forms and meandroid branching colonies together with some massive forms mostly inhabited the low-energy conditions of the lower euphotic to oligophotic zones of the middle ramp. In the middle parts of the mixed carbonate–siliciclastic ramp, sparse pillarstone together with domestone comprises a mixstone coral growth fabric. Fluctuations in nutrient and clastic sediment input, salinity and the growth of red algae likely terminated coral growth. 相似文献
9.
10.