10块新疆哈密沙漠陨石的岩石矿物学特征和类型划分及该地区陨石富集机制探讨

发布时间：2018-01-17 03:14

  本文关键词：10块新疆哈密沙漠陨石的岩石矿物学特征和类型划分及该地区陨石富集机制探讨　出处：《中国科学院研究生院(广州地球化学研究所)》2015年硕士论文　论文类型：学位论文

  更多相关文章： 沙漠陨石 富集机制 陨石分类 岩石学 矿物成分

【摘要】：陨石是从行星际空间穿越大气层烧蚀后到达地表的流星残留体,代表了太阳系不同时间和空间的演化产物。我国有世界上公认最早、最可靠的陨石记录,但历史上收集并保存下来的陨石数量不多,类型不全。除从南极获得的大量陨石样品外,国内搜寻到的陨石样品较少。沙漠是除南极地区之外的另一陨石富集区域,我国地域辽阔尤其是拥有面积广阔的沙漠地区,为陨石的保存提供了有利的地理条件。因此,寻找和回收沙漠陨石,对我国在该领域的研究将起到极大的促进作用。陨石分类是根据陨石岩石-矿物学以及成分特征确定陨石类型,是陨石开展深入研究的基础。本文通过对我国首次开展的专业陨石搜寻进行地形、气候和陨石聚集情况分析,探讨陨石的富集机制,尝试建立该地区陨石富集模型,以期为我国后续沙漠陨石的搜寻提供借鉴。哈密沙漠和附近戈壁地区由于气候干旱、少或无植被、人迹稀少,为降落在该地区陨石的长期保存提供了有利的气候条件。本次收集区域主要位于库姆塔格沙垄两侧,两侧风向相对,于沙垄处交汇,这也是沙垄地形的形成原因,因此,风的推进使分散陨石随其它沙石一起朝沙垄方向运移。在运移方向遇凸起地形也会阻挡运移物通过,而出现富集。此次搜寻在沙垄两侧圈定四个区域(分别记为I区,II区,III区和IV区)。除II区和III区区内存在零散陡峭的风蚀残丘外,区内总体地势平坦,区域周边存在凸起地形阻挡的小残丘。其中,I区位于库姆塔格沙垄西侧约20公里,南部靠近阿拉塔格山脉;II区位于库姆塔格沙垄东侧约50公里,南部靠近雅满苏镇;III区位于库姆塔格沙垄东侧约5公里,是最靠近沙垄的搜寻区;IV区位于库姆塔格沙垄东侧约20公里,靠近南湖乡,是最靠北的搜寻区。I区搜集到42块陨石,朝沙垄方向,陨石质量呈现减小的趋势;II区、III区和IV区收集到的陨石质量均大于100g,最重约700g,且发现位置在残丘坡脚附近,可能是降落在斜坡上的陨石在重力作用下滚落到山脚造成的。因此,哈密沙漠陨石的主要富集区域具以下几个特点:1)顺风方向阻挡物之前更富集;2)沙垄附近地形平坦处富集;3)较陡残丘坡脚处富集。此次新疆哈密沙漠陨石搜寻共收集到46块陨石样品,本文选取其中10块代表性陨石,无水条件下磨制成光片和薄片,进行岩石学、矿物学和矿物组成化学成分特征研究,并对其进行类型划分,确定它们的化学群、岩石类型、风化程度、冲击变质程度。光片和薄片在光学显微镜下进行岩相观察,包括球粒和基质的结构特征、不透明矿物的种类、含量和分布、冲击变质特征和风化程度。10块陨石均具球粒结构,为典型的普通球粒陨石。1块样品Kumtag014球粒非常清晰,类型多样,基质未发生重结晶,岩石类型为3型。其余9块陨石经历了明显的热变质作用,基质中等重结晶,球粒轮廓模糊,但仍然可以分辨,定为5型。3块陨石(Hami003、Hami004和Kumtag014)仅金属周边发生轻微的褐铁矿化,风化类型为W1型;6块陨石(AM007、AM008、AM011、AM015、AM020、Hami005)铁镍金属和陨硫铁部分被氧化成褐铁矿,风化类型为W2型;1块陨石(AM027)铁镍金属和陨硫铁发生强烈氧化,定为W3型。1块陨石(Kumtag014)橄榄石颗粒完整,无裂隙,无金属熔滴,冲击类型定为S1型;4块陨石(AM015、AM020、AM027和Hami004)橄榄石有裂隙,无金属熔滴,定为S2型;5块陨石(AM007、AM008、AM011、Hami003和Hami005)金属熔滴广泛分布,定为S3型。硅酸盐和不透明矿物化学成分由电子探针进行测定。电子探针定量分析的实验条件是加速电压15k V、束流20n A,硅酸盐采用天然矿物标样,金属采用金属或氧化物标样。分析数据采用ZAF(原子序数、吸收效应及荧光效应)法校正。Kumtag014(Fa9.1-48.3,PMD=51.0;Fs2.8-30.3,PMD=54.2)属于L群,组成矿物化学成分变化大。依据橄榄石Fa的相对标准偏差(PMD=51.0)将其进一步划分为3.4亚型,属于相当原始的球粒陨石样品;AM007、AM008、AM011、AM015、AM020、AM027和Hami004,7块陨石(Fa22.6~25.9,Fs17.6~21.4)属于L群;Hami003、Hami005,2块陨石(Fa18.2~20.8,Fs16.0~17.8)属于H群。
[Abstract]:Meteorites are from interplanetary space through the atmosphere after the ablation to the surface of the meteor residue, which represents the product evolution of solar system in different time and space. China has the world recognized the earliest, most reliable meteorite record, but the history of the collection and the number of meteorites preserved much, incomplete type. In addition to a large number of meteorites from the Antarctic, home to search the meteorite samples less. The desert is another Antarctic meteorites except outside the region rich area, China is a vast country especially with the desert area of the vast area, provide favorable geographical conditions for the preservation of the meteorite. Therefore, search and recovery of desert meteorites, will play a great to promote research in the field of our country. According to the classification of meteorite meteorite types determine the meteorite rock mineralogy and composition characteristics, is the basis for further research. Based on the meteorite carried out in China for the first time To carry out professional search for meteorites terrain, climate analysis and aggregation of meteorites, meteorites enrichment mechanism, try to establish the reference area meteorites enrichment model, in order to search for China's future. The Hami desert and desert meteorites near the Gobi area because of the dry climate, with little or no vegetation, sparsely populated, provide favorable the climate conditions for the long-term preservation of land in the area. The meteorite collection areas are mainly located in kumutage sand ridge on both sides, both sides of the wind relative, at dune interchange, which is also the reasons for the formation of sand dune terrain, the wind dispersed with other meteorites advancing together in the sand dunes. In case of convex direction migration the terrain in migration direction will stop migration through, and enrichment. The search in the sand ridges on both sides delineated four regional (referred to as I area, II area, III area and IV area). In addition to the II district and III District in zero memory Bulk erosion monadnock steep, the overall area is flat, area surrounding the existence of hill barrier little monadnock. Among them, the I area is located about 20 kilometers west of kumutage sand ridge, south near arrata lattice mountains; II area is located about 50 kilometers east of kumutage sand ridge, south near the Yamansu town; III District is located about 5 km east of kumutage sand ridge, is the most close to the sand dunes of the search area; IV area is located about 20 kilometers east of kumutage sand ridge, near South Lake Township, is the northernmost search zone.I collected 42 meteorites, in the sand ridge direction, reduced trend meteorite quality; II area, III area and IV area to collect the quality of meteorites were more than 100g, the weight is about 700g, and found the location in the vicinity of the residual hill slope, may be landed on the slope under the action of gravity meteorite fallen to the mountain caused. Therefore, the main rich Hami desert meteorites set out the following areas Features: 1) before the direction of wind barrier more enrichment; 2) sand dunes near the flat terrain at a steep slope enrichment; 3) enrichment. The monadnock Xinjiang Hami desert meteorite search collected 46 meteorite samples, this paper selects 10 representative meteorites, anhydrous conditions polished and thin film to study on the characteristics of petrology, mineralogy and Mineral chemical composition, and classified into different kinds, determine their chemical groups, rock types, weathering degree, degree of shock metamorphism. Light sheet and sheet by petrographic observation under optical microscope, the structure features including chondrules and matrix, kinds of opaque minerals, content and distribution, shock metamorphic features and the weathering degree of.10 meteorites are variolitic texture, as ordinary chondrites.1 samples Kumtag014 chondrules typical is very clear, various types of matrix recrystallization did not occur, the rock type is the type 3. 浣，

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