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771.
Jacques Barbier 《Physics and Chemistry of Minerals》1996,23(3):151-156
New germanate analogs of the mineral surinamite, Mg3Al4BeSi3O16, have been synthesized with composition Mg4A4Ge3O16 (A=Al, Ga) and have been characterized by powder X-ray diffraction and transmission electron microscopy. The Al surinamite phase crystallizes with a primitive unit-cell (P2/n, a=10.153(1), b=11.708(2), c=9.920(1) Å, β=110.18 (2)° and Z=4) similar to that of the silicate mineral. The Ga surinamite-like phase crystallizes with a larger unit-cell (C2/c, a=10.308(2), b=23.690(5), c=10.057(l) Å, β=110.23 (2)° and Z=8). High-resolution electron microscopy has shown the common formation of intergrowths between the surinamite and sapphirine structures, illustrating the polysomatic structural relationship between them. Observations of disordered microstructures in the Al surinamite suggest the occurrence of a P2/n?C2/c transformation. 相似文献
772.
新疆北部古生代大陆增生构造 总被引:35,自引:2,他引:35
古生代亚洲中部是一幅两陆夹一洋、洋中多地体的构造图案,大地构造框架与现代西南太平洋格局十分相似。中亚造山带是晚古生代复杂地体的拼贴带。新疆北部古生代存在4类成因的8个地体构造。它们以裂解陆块地层块体、海山和火山弧的形式散布在中蒙大洋中,诸地体间是一系列的小洋盆。晚古生代,这些地体开始彼此拼贴并导致强烈推覆作用。石炭纪末-二叠纪初,中蒙大洋闭合,散布其中的诸地体分别增生到塔里木大陆北缘和西伯利亚大陆南缘。北天山-准噶尔地区6条蛇绿岩带记录了诸地体间碰撞事件。 相似文献
773.
王博 舒良树 Cluzel D Faure M Charvet J 马前 吴华 徐兴旺莫新华梁光河程松林秦克章李 军张宝林王 杰肖骑彬 韩照举金长明李金祥 《中国地质》2006,33(3):498-508
石炭纪火山岩广泛分布于西天山伊犁陆块周缘,其岩性复杂,并大多与陆源碎屑岩伴生或互层。其中伊宁阿希、尼勒克和那拉提3个剖面的火山岩岩石地球化学特征显示,这些火山岩属于钙碱性系列,由玄武岩、粗玄岩、玄武质安山岩、玄武质粗面安山岩、安山岩、流纹岩、英安岩和粗面岩组成。稀土元素含量较高,轻稀土元素较重稀土元素富集。这些火山岩亏损高场强元素Nb,Ta,Zr等,而富集大离子亲石元素Th,Rb等,因而这些岩石的形成与板块俯冲有关。微量元素地球化学图解进一步表明,这些岩石形成于大陆岛弧环境。与之共生的早、中石炭世浅海—滨海相沉积地层以及伊犁陆块北缘巴音沟—莫托沙拉沟晚泥盆世—早石炭世蛇绿岩带的存在,表明伊犁陆块北缘在石炭纪时其环境为活动大陆边缘,石炭纪火山岩的形成可能与晚泥盆世—中石炭世早期北天山洋盆向南的俯冲作用有关。 相似文献
774.
Grard Brogniez Frdric Parol Laurianne Bcu Jacques Pelon Olivier Jourdan Jean-Franois Gayet Frdrique Auriol Christian Verwaerde Jean-Yves Balois Bahaiddin Damiri 《Atmospheric Research》2004,72(1-4):425
In the context of the next AQUA Train satellite experiment, airborne measurements were carried out to simulate satellite measurements. They were conducted between September 25 and October 12, 2001, off the coast of southern France over the Atlantic Ocean and over the Mediterranean Sea, respectively. During the intensive Field Radiation Experiment on Natural Cirrus and High-level clouds (FRENCH/DIRAC 2001), natural ice clouds were sampled from in situ and remote sensing measurements. On October 5 and 7, 2001, cirrus cloud decks were described by a complete data set acquired by: (i) in situ microphysical instruments onboard the TBM-700 aircraft: PMS probe, and Polar Nephelometer (ii) and downward-looking radiative instruments onboard the Mystère 20 aircraft: an infrared radiometer, a lidar, a visible imager with polarisation capabilities, and a middle infrared radiometer. Moreover, classical thermodynamical measurements were carried out onboard the Mystère 20. Mean microphysical characteristics of cirrus deck are derived from interpretation of remote sensing measurements. These properties are compared with those derived from in situ microphysical measurements in order to evaluate the radiative impact of natural cirrus clouds. 相似文献
775.
Southern India and Sri-Lanka are the places where "incipient charnockites",i.e.the local transformation of amphibolite-facies gneisses into orthopyroxene-bearing,igneous looking charnockites,have been discovered in the early sixties.The fact that some incipient charnockites occur along a network of brittle fractures,together with CO_2 remnants preserved in mineral inclusions,had called for the role of fluids during charnockite alteration.The present work presents new observations on fluid inclusions and microtextures of incipient charnockites from type localities in southern India.In addition to CO_2-rich fluid inclusions in quartz and feldspar,all of the occurrences have disrupted remnants of concentrated aqueous alkali chloride solutions.CO_2 inclusions are more abundant in paragneiss(Kerala)than in orthogneiss(Karnataka/Tamil Nadu).The finding of disrupted brine inclusions in the Kabbal charnockite is a key link between closely associated massive charnockites and Closepet Granite,both of which also share the brine remnants.All of the occurrences studied here have feldspar or feldspar-quartz microvein networks along grain boundaries of recrystallized quartz,feldspar and orthopyroxene.These metasomatic veins again indicate the action of alkali-exchanging fluids(i.e.,saline solutions).Feldspar microveins,which have been found in most "massive" charnockites,along with the CO_2-rich fluid inclusions,suggest a commonality of incipient charnockite and massive charnockite,both types differing in intensity of interaction with metasomatizing pore fluids. 相似文献
776.
This study aims at understanding the physico-chemical interactions between the saturated brine and the rocks enclosing the
underground salt workings in Lorraine (eastern France). These anhydrite-rich and argillaceous rocks were characterized in
terms of mineralogy, micro-texture and connected porosity. Then, the two main lithofacies, massive anhydrite and anhydrite-rich
argillite, were immersed in brine during more than 1 year. During this batch experiment, the argillites were affected by macroscopic
splitting, contrarily to the massive anhydrite. Micro-texture and brine chemical analyses clearly show the swelling due to
the hydration of anhydrite into gypsum inside the argillites, whereas hydration occurs superficially on the massive anhydrite,
due to its very low permeability. Anhydrite–gypsum transformation is promoted by the presence of dissolved strontium and potassium
in saturated brine. The low activity of water in saturated brine does not allow the clay fraction to swell significantly during
the experiment. Thus, the expansion resulting from the hydration of anhydrite into gypsum might be responsible of the splitting
of argillite in a saturated brine environment. The superficial anhydrite hydration on massive anhydrite can be explained by
the low amount of connected porosity (less than 1%). 相似文献