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1.
为了更好地确定火星不同地形所记录的气候变化的时间尺度,确定火星历史上重大事件的绝对年龄,并校准陨石坑率,需要从火星原地或从返回样品中获得精确的年龄数据.原地K-Ar定年是目前比样品返回更为实用的一种精确远程定年技术.黄钾铁矾(KFe3(SO4)2(OH)6),是火星上广泛存在的唯一一种通过就位探测、轨道遥感探测、陨石研究三种手段都确定存在的含钾硫酸盐矿物,它已被用于K-Ar和40Ar/39Ar精确定年.火星上黄钾铁矾的保存提供了火星上含水过程的性质和持续时间的信息,不同年龄的黄钾铁矾能有效地解读火星历史上地表水流动时期及过渡到当前干旱气候之间的演变历史.本文总结了近年来火星上黄钾铁矾存在的区域、矿物学特征、在火星上的稳定性、原地K-Ar定年的研究现状、黄钾铁矾氩扩散动力学等,探讨了黄钾铁矾原地K-Ar定年的关键科学问题、火星采样返回需求、未来研究方向等.  相似文献   

2.
新疆吐哈地区有色金属矿山上部氧化带中,发现了一种新的含K硫酸盐矿物-斜钾铁矾(KFe(SO4)2),含K量较高.若能应用40Ar/39Ar法测定该矿物年龄,可以研究该地区干旱化的时间、过程,从而探讨青藏高原隆升或两极冰盖的形成演化对于该地区气候的影响.但是,吐哈地区温度可达60℃,长时间的高温是否会引起矿物中的Ar的丢失?矿物颗粒细小是否会引起矿物中的Ar的丢失?这对于矿物年龄的解释具有重要意义.本文根据扩散理论,应用阶段加热的方法进行Ar的扩散特性研究,在此基础上,应用简单的内生长-扩散模型模拟了可能的高地表温度和矿物颗粒大小对样品年龄的影响.实验结果表明斜钾铁矾中Ar的扩散频率因子logD0/a2=13.71/s,活化能Ea=71.30kcal/mol,封闭温度Tc为294℃(假设冷却速率为10℃/Ma),活化能和封闭温度较高.而且,模拟结果表明斜钾铁矾形成后,在外界环境下温度和矿物颗粒大小对年龄几乎没有影响.在误差范围内重复性测试结果基本一致,进一步证明斜钾铁矾适用于40Ar/39Ar定年.  相似文献   

3.
正对于中国西北部地区干旱化的时间及原因,国内外的科学家进行了大量的研究,但是现在还存在激烈的争论。黄钾铁矾等含钾硫酸盐矿物通常形成于干旱-半干旱气候条件下,并保存于极端干旱气候条件下,因此对这类矿物进行40 Ar/39 Ar定年,不仅可以得到大陆化学风化的时间序列,还可以反演区域的古气候特征。本文通过对吐哈盆地2个矿床氧化带:红山铜金矿床和彩华沟铜-硫多金属矿床中表生含钾硫酸盐矿物40 Ar/39 Ar定年的研究,探索和验  相似文献   

4.
表生明矾石族矿物40Ar/39Ar年代学概述   总被引：2，自引：0，他引：2       下载免费PDF全文
杨静  郑德文  武颖 《地震地质》2013,35(1):177-187
近年来,激光40Ar/39Ar法成功测定了硫化物矿床氧化带中表生明矾石族矿物(明矾石和黄钾铁矾)的年龄,表明这类矿物适用于 40Ar/39Ar法定年。激光熔样方法引入40Ar/39Ar定年,不仅减少了样品的用量,同时也降低了系统的空白本底水平; 利用阶段加热法得到的年龄谱图,不仅可以有效识别原生矿物的混染和多世代矿物的存在,还可以检测样品中的过剩、继承Ar。虽然风化矿物定年还存在一些潜在的问题,但是只要有科学的采样和合理的分析流程,并结合其他检测手段,就可以获得有意义的风化年龄。这为研究新生代以来化学风化、氧化带形成时间和古气候提供了新的方法。  相似文献   

5.
长乐-南澳韧性剪切带~(40)Ar/~(39)Ar热年代学研究   总被引：13，自引：2，他引：13  
采自长乐-南澳韧性剪切带的5个单矿物~(40)Ar/~(39)Ar坪年龄分别为107.9 Ma(Mus)、108、2Ma(Bi),107.1 Ma(Bi),109.2 Ma(Hb)和117.9 Ma(Bi),与对应的等时线年龄一致.它们记录了长乐-南澳韧性剪切带的形成时间.样品在不同封闭温度下的年龄重叠说明,作为闽粤沿海碰撞造山带主体之一的长乐-南澳韧性剪切带在形成后(107～118 Ma)经历了快速的初始冷却上升.结合钾长石K-Ar年龄研究和相关的年代学资料表明,该带后期(107～70 Ma)冷却上升速率有所减缓,大约为0.18～1.12mm/a.  相似文献   

6.
新疆西准噶尔包古图斑岩铜矿年代学研究   总被引：1，自引：0，他引：1  
西准噶尔包古图铜矿是近几年新疆发现的又一个中型斑岩铜矿,其成岩成矿年代学的研究可以对矿床成因、区域成矿规律的认识有更好的制约.包古图地区出露一系列中酸性小岩体,前人按照出露面积大小将这些岩体编号为Ⅰ-Ⅹ号.目前,Ⅴ号岩体已经进行了详勘,探明为中型铜矿,其他几个岩体也都程度不同的投入了勘探工作量,并且发现了较好的成矿迹象.本文利用锆石SHRIMP U-Pb法和单矿物K-Ar法对Ⅴ号岩体进行了成岩成矿年代学研究,其中锆石25个测点的^206Pb/%238USHRIMP年龄大致可以分为加权平均值（335.6±7.8）Ma和（311.4±3.3）Ma的两组,前者被解释为捕获锆石,可能来源于包古图组凝灰岩或者深部的花岗质岩基,有待于进一步研究;后者为含矿岩体侵位年龄.本次研究获得成矿期黑云母的K-Ar年龄为（296.0±3.7）Ma和（297.3±3.8）Ma,结合我们以前所获得的辉钼矿Re-Os年龄310Ma,确定成矿时代为310~296Ma.花岗斑岩和闪长玢岩脉的K-Ar年龄为278~240Ma,根据穿插关系可以判定它们为成矿后脉岩.据此基本建立了包古图斑岩铜矿成岩成矿年代学框架.  相似文献   

7.
青藏高原的隆升与扩展不仅导致欧亚大陆内部发生强烈的构造变形,亦对高原周缘的地貌格局及气候变化产生了重大影响.青藏高原东北缘新生代以来的隆升时代与响应过程一直备受争议,而界定青藏高原东北缘构造带隆升时序是解决争议的关键之一.本研究围绕青藏高原东北缘,在陇中盆地、六盘山褶皱逆冲带和鄂尔多斯地块西南缘地区进行了磷灰石和锆石裂变径迹测试分析和热史模拟.测试分析结果表明研究区样品的磷灰石裂变径迹年龄范围分布于136～16 Ma,裂变径迹的长度范围介于11.9～13.3μm;锆石裂变径迹年龄结果为258～79 Ma,但多数样品的年龄介于160～99 Ma;热史模拟结果揭示了研究区新生代以来至少经历了两期隆升和冷却降温事件,即始新世期间(55～30 Ma)和中中新世(17～12 Ma)以来.始新世期间(55～30 Ma)发生的隆升事件可能是印度大陆与欧亚大陆陆陆碰撞远程效应的直接响应,表明印度与欧亚大陆碰撞之初或不久,其应力即已传导至东北缘边界;中中新世(17～12 Ma)以来的隆升剥露冷却事件奠定了青藏高原东北缘现今构造格局.  相似文献   

8.
博格达山链新生代抬升过程及意义   总被引：4，自引：0，他引：4  
东天山的博格达-巴里坤山链是在晚古生代造山以及中生代伸展基础上于新生代强烈抬升而成,其新生代再造山和隆升是欧亚大陆地质史上的标志性重要事件,造就了东天山现今的盆山地貌格局.运用低温热年代学方法,通过系统批量采样,获得了博格达山链新生代抬升过程的3个明显阶段：5.6-19,20-30和42-47Ma,其中20-30Ma是最显著的一期隆升,而且是山链整体的统一隆升,这与西天山以及青藏高原北部同期的构造事件相似.因此,该期隆升意味着青藏高原向北扩展已经影响到了天山一线,同时获得隆升的起动时间为不晚于65Ma,其动力机制是否是印度-欧亚板块开始碰撞的响应目前还不清楚.裂变径迹结果表明,整个博格达-巴里坤山链在整个新生代的构造活动是分阶段的,各期之间具有整体抬升和差异抬升之分,而且沿山体的东西方向和南北方向上具有明显的差异性,表现为隆升由西向东和由北向南迁移,山体以向南的横向扩展为主要趋势.东天山新生代的3期构造事件与青藏高原尤其是高原北部构造事件都能比较好的对应,因此东天山新生代的构造事件很可能是青藏高原尤其是北部演化的响应.  相似文献   

9.
长江三角洲晚新生代地层独居石年龄谱与长江贯通时间研究   总被引：13，自引：0，他引：13  
PD-99孔位于长江三角洲南翼, 揭示的晚新生代地层厚313 m. 独居石年龄谱表明, 上新统以350~500 Ma的颗粒为主, 第四系则以100~275 Ma的颗粒为主, 反映二者母源区发生了变化. 晚于25 Ma的独居石颗粒初现层位于高斯正极性带与松山负极性带界线之上(约在2.58 Ma), 这是青藏高原隆升对东中国海沉积产生直接影响的开端. 长江河口地层中晚于25 Ma独居石含量变化分为两大阶段, 分别对应于早、中更新世青藏高原的快速隆升和晚更新世以来的最强烈隆升.  相似文献   

10.
腾冲火山活动的时代和岩浆来源问题   总被引：35，自引：0，他引：35       下载免费PDF全文
47个腾冲火山岩样品的K-Ar年龄值域在0.09和17.84Ma之间。4条火山岩的40Ar/36Ar-40K/36Ar等时线年龄分别为2.93、0.81、0.31和0.13Ma。火山喷发的时代从中新世到更新世,喷发的高潮在晚更新世。腾冲火山目前还不是死火山,而腾冲及其邻区的热事件（侵入-热变质-喷发）又是连续发生的。20个样品的Rb和Sr含量、稳定Sr同位素初始比（0.70578-0.71437）以及其它地球化学资料还表明,这些火山岩是属于板块碰撞带生成的高钾钙碱性岩浆系列。火山岩的母岩浆来源于地幔的玄武岩浆,但在上升过程中受到过富含放射性成因Sr的地壳物质的强烈渐进混染。  相似文献   

11.
The Tianshan Mountains,located in the northwestern China,are bounded by the Tarim Basin to south and the Junggar Basin to north.In the north piedmont of this mountain range,ongoing thrusting and folding forms a set of roughly parallel anticlines.Geological observations predicted that averaged over last~1 Ma time scale,the shortening rates of these anticlines are about2.1–5.5 mm/a;However by averaged over about 10±2 kyr,their shortening rates reduce to merely about 1.25±0.5 mm/a.The slow shortening of the anticlines in the last~10±2 kyr is coarsely concurrent in time with the last global deglaciation.Here,we use a two-dimensional finite element model to explore crustal deformation across north piedmont of the Tianshan Mountains under various erosion-sedimentation conditions that are assumed to represent the climate-controlled surface process.Numerical experiments show that with a relatively weak erosion-sedimentation strength,the crustal shortening is accommodated mainly by north piedmont of the Tianshan Mountains,similar to the high shortening rate of anticlines averaged over the last~1Ma.By increasing erosion-sedimentation strength,the resultant crustal shortening is transformed gradually toward the Tianshan Mountains,resulting in the shortening rate in its north piedmont being decelerated to what is observed as averaged over the last~10±2 kyr.This result suggests that erosion and sedimentation could play an important role mechanically on strain localization across an intra-continent active tectonic belt.Hence,if the climate change around the last global deglaciation could be simply representative to the enhancement of surface erosion and sedimentation across the pre-existed Tianshan Mountains and its foreland,our models indicate that the observed shortening-rate variations averaged over~1 Ma and~10±2kyr time scales around north piedmont of the Tianshan Mountains should be resulted from climate changes.  相似文献   

12.
本文对黄土高原和天山黄土区表土进行系统的岩石磁学和粒度测试分析,探讨了表土磁性特征及其环境意义,结果表明表土中的强磁性矿物均为磁铁矿和磁赤铁矿,弱磁性矿物为赤铁矿和纤铁矿或针铁矿,黄土高原黄土地层中的磁赤铁矿至少有部分属于风积成因.黄土高原表土中磁化率与频率磁化率呈良好的正相关,气候作用是主导黄土高原表上磁化率增强的主...  相似文献   

13.
In arid zones, many active aeolian dunes terminate at ephemeral and perennial desert rivers. The desert rivers show very high rates of sediment transport that cause deleterious downstream effects on the river system and ecology. High sediment loading has been attributed to severe water erosion of sparsely covered watersheds during infrequent but heavy rainfall. Although aeolian erosion is known to lead to high rates of wind‐blown sand transport, direct confirmation of whether the aeolian processes accelerate or inhibit fluvial sediment loss is lacking. Here, we show that an aeolian‐fluvial cycling process is responsible for the high rate of suspended sediment transport in a Sudalaer ephemeral desert channel in the Ordos Plateau of China. Frequent aeolian processes, but low frequency (once every 3 years on average) flooding, occur in this region. Wind‐blown saltating grains appeared to be unable to cross the desert channel because of interruption of channel‐induced recirculating air flow, and therefore tended to settle in the channel during the windy seasons, leading to channel narrowing. During flooding, this narrowed channel was found to yield a threefold increase in suspended sediment loading and a 3.4‐fold increase in the weight percentage of the 0.08–0.2 mm sediment fraction on 18 July 2012. Loss of stored aeolian sand due to channel erosion accounted for about half of the total sediment yield in this watershed. These findings show that aeolian processes play an essential role in accelerating the sediment yield from a watershed characterized by aeolian‐fluvial interplay and also suggest that the drier the region and the greater the aeolian process, the more the aeolian process contributes to fluvial sediment yield. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

14.
The Bolokonu-Aqikekuduke fault zone(Bo-A Fault)is the plate convergence boundary between the middle and the northern Tianshan. Bo-A Fault is an inherited right-lateral strike-slip active fault and obliquely cuts the Tianshan Mountains to the northwest. Accurately constrained fault activity and slip rate is crucial for understanding the tectonic deformation mechanism, strain rate distribution and regional seismic hazard. Based on the interpretation of satellite remote sensing images and topographic surveys, this paper divides the alluvial fans in the southeast of Jinghe River into four phases, Fan1, Fan2, Fan3 and Fan4 by geomorphological elevation, water density, depth of cut, etc. This paper interprets gullies and terrace scarps by high-resolution LiDAR topographic data. Right-laterally offset gullies, fault scarps and terrace scarps are distributed in Fan1, Fan2b and Fan3. We have identified a total of 30 right-laterally offset gullies and terrace scarps. Minimum right-lateral displacement is about 6m and the maximum right-lateral displacements are(414±10)m, (91±5)m and(39±1)m on Fan2b, Fan3a and Fan3b. The landform scarp dividing Fan2b and Fan3a is offset right-laterally by (212±11)m. Combining the work done by the predecessors in the northern foothills of the Tianshan Mountains with Guliya ice core climate curve, this paper concludes that the undercut age of alluvial fan are 56~64ka, 35~41ka, 10~14ka in the Tianshan Mountains. The slip rate of Bo-A Fault since the formation of the Fan2b, Fan3a and Fan3b of the alluvial-proluvial fan is 3.3~3.7mm/a, 2.2~2.6mm/a and 2.7~3.9mm/a. The right-lateral strike-slip rate since the late Pleistocene is obtained to be 3.1±0.3mm/a based on high-resolution LiDAR topographic data and Monte Carlo analysis.  相似文献   

15.
使用全站仪实测了天山南麓北轮台逆断裂库尔楚段阿克艾肯－喀腊萨喀腊阿塔木冲洪积扇断层崖地形地貌，采用^10Be测年方法测定了该冲洪积扇的形成年龄，得到该断裂段垂直位移滑动速率为0.48mm/a、0.85-1.0mm/a和1.52mm/a，并对该断裂段的水平缩短速率和天山第四纪水平缩短量进行了讨论。  相似文献   

16.
The relationship between the terrestrial ecosys-tems and the climate change is one of the importantfields in the study on global change,and the rela-tionship between vegetation and climate change is oneof the main research focuses[1―3].On the one hand,the high-amplitude global warming results in the increase of evaporation from the oceans and the waters on land and of precipitation in most parts of the oceans and theterrestrial regions,thus,the modern glaciers are seri-ously melted,the runoff …  相似文献   

17.
借助分布在北天山地区最新GPS点位的运动观测资料, 利用GAMIT/GLOBK数据处理软件获取了北天山地区现今地壳的运动位移场． 以该位移场为基础, 利用弹性半空间位错理论, 估算了研究区内博罗科努—阿其克库杜克断裂和准噶尔盆地南缘断裂两条具有代表性的主要断裂的现今活动速率． 结果表明: 博罗科努—阿其克库杜克右旋走滑断裂东、 西两段滑移速率的差异性不明显, 1944年3月10日乌苏南MS7.2强震发生后, 该断层现今表现为震后微蠕滑运动, 东、 西两段滑动速率均在1—2 mm/a之间; 准噶尔盆地南缘断裂现今滑动速率为(5.6±1.0) mm/a．   相似文献   

18.
喀什河断裂带古地震研究   总被引：3，自引：2，他引：3       下载免费PDF全文
喀什河断裂带是我国北天山西段一条规模较大的活动断裂,第四纪以来垂直运动速率为3.8毫米/年,现今地震活动频繁。历史上曾发生过1812年尼勒克8级地震,沿断层带造成长达80公里的形变带,史前地震也很活跃,经初步研究,断裂带至少发生过两次古地震活动,大震复发周期为2000—2500年  相似文献   

19.
现代的天山山脉是在古生代造山基础上,于新生代强烈抬升而形成.其新生代造山和隆升过程,造就了现今的天山地貌格局.本文选取西南天山作为研究区域,采用河床砂岩屑裂变径迹测年分析,从统计角度限定西南天山的隆升-剥露过程.样品采集于特克斯河支流阿克雅孜河、夏特河、木扎河以及特克斯河干流的沉积河床.磷灰石裂变径迹测试和统计分析表明,存在代表源区热史演化不同阶段的年龄峰值.尽管不同样品的年龄众数分布有少许差别,颗粒年龄众数的去褶积分析获得了西南天山山体新生代冷却的三个基本一致的阶段：6~8 Ma,12~19 Ma以及32~40 Ma.结合山脉隆起的地质地貌模型,无论是整体抬升或掀斜抬升,以及压扭性背景的花状挤出抬升,根据磷灰石裂变径迹封闭温度推断的抬升量与现今天山高度基本相当的事实,都可以确认西南天山山体是6~8 Ma以来形成的.天山这三期快速抬升冷却事件与青藏高原及其周边的主要隆升时期有较好的对应,证明了天山隆升和印度-欧亚板块碰撞远程效应的关系.另外,6~8 Ma的冷却事件与沉积地层学研究揭示的6 Ma左右的气候显著变化相互印证,显示了研究区域山脉隆升和气候变化之间存在的密切关系.  相似文献   

20.
Chronostratigraphic records in the drylands of north China provide basic archives to reveal the dynamic connections between climate changes and the behaviour of aeolian systems. However, the interpretation of aeolian chronostratigraphy is not straightforward and may be associated with significant uncertainty due to a number of external and localised forces. Taking into account this complexity of aeolian systems, excluding preservation and sampling bias from palaeoclimatic signals requires that the interpretation of chronostratigraphic records be based on as many dates from as many sites as possible. Optically stimulated luminescence (OSL) dating provides a direct way to date aeolian sediments. However, the determination of equivalent dose (De) using the commonly applied single-aliquot regenerative dose (SAR) protocol is relatively time-consuming for samples with burial doses exceeding 50 or 100 Gy.In this study, the global standardised growth curve (gSGC) method is applied to multi-grain aliquots of coarse quartz from various sites covering a wide region of the south margin of the Tengger Desert in north China to rapidly determine De for a large number of aliquots and samples. The large between-aliquot variability in the shape of the dose response curve (DRC) is significantly reduced using a least-squares normalisation procedure. The results of a leave-one-out cross-validation (LOOCV) protocol demonstrates that De values determined using the gSGC and SAR methods are very consistent with each other up to at least 200 Gy and 400 Gy, for the 90–150 μm and 63–90 μm fractions, respectively. It suggests that the gSGC protocol can be used as an efficient procedure for De determination of a large number of aeolian samples from multiple sites. This in turn provides a better constraint for the interpretation of Late Quaternary aeolian chronostratigraphic records in drylands of north China.  相似文献   

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