共和盆地黏土矿物与孢粉记录的末次冰消期以来的气候环境相位差   总被引：1，自引：1，他引：0  

孙庆峰  程波  赵黎 《中国沙漠》2014,34(5):1237-1247

在青藏高原北缘共和盆地达连海钻取了40.92 m沉积柱,其¹⁴C年代有10个控制点,底部年龄最大值为14.5 cal ka BP,沉积柱为末次冰消期以来的湖泊沉积物。在沉积柱中按20 cm/70 a分辨率选出200个样品进行了黏土矿物、粒度、碳酸盐、沉积速率等非生物指标与生物指标的孢粉等多项指标的综合分析。结果表明：末次冰消期以来,达连海沉积柱中非生物指标与生物指标反映的气候和环境变化阶段的显著性不同,反映的气候环境的变化阶段也不尽一致,出现气候环境的相位差。冰消期黏土矿物非生物指标与孢粉生物指标有约1.0~1.2 ka的相位差;早、中全新世黏土矿物反映的气候变化时段较孢粉指标指示的时段滞后约1.0 ka;在晚全新世黏土矿物反映的气候变化较孢粉滞后约0.1 ka。造成黏土矿物和孢粉反映气候环境相位差的原因是孢粉和黏土矿物对气候响应的差异性、黏土矿物和孢粉搬运方式的不同、气候条件及其转换、地貌等多因素的综合影响。  相似文献   

Crust and upper mantle structures beneath Northeast China from receiver function studies          下载免费PDF全文

Zhen Guo  Yuliang Cao  Xianguang Wang  Y. John Chen  Jieyuan Ning  Weiguang He  Youcai Tang  Yongge Feng 《地震科学（英文版）》2014,27(3):265-275

P-wave and S-wave receiver function analyses have been performed along a profile consisted of 27 broadband seismic stations to image the crustal and upper mantle discontinuities across Northeast China. The results show that the average Moho depth varies from about 37 km beneath the Daxing’anling orogenic belt in the west to about 33 km beneath the Songliao Basin, and to about 35 km beneath the Changbai mountain region in the east. Our results reveal that the Moho is generally flat beneath the Daxing’anling region and a remarkable Moho offset (about 4 km) exists beneath the basin-mountain boundary, the Daxing’anling-Taihang Gravity Line. Beneath the Tanlu faults zone, which seperates the Songliao Basin and Changbai region, the Moho is uplift and the crustal thickness changes rapidly. We interpret this feature as that the Tanlu faults might deeply penetrate into the upper mantle, and facilitate the mantle upwelling along the faults during the Cenozoic era. The average depth of the lithosphere-asthenosphere boundary (LAB) is ~80 km along the profile which is thinner than an average thickness of a continental lithosphere. The LAB shows an arc-like shape in the basin, with the shallowest part approximately beneath the center of the basin. The uplift LAB beneath the basin might be related to the extensive lithospheric stretching in the Mesozoic. In the mantle transition zone, a structurally complicated 660 km discontinuity with a maximum 35 km depression beneath the Changbai region is observed. The 35 km depression is roughly coincident with the location of the stagnant western pacific slab on top of the 660 km discontinuity revealed by the recent P wave tomography.  相似文献   

日本海沟俯冲带热结构与深源地震   总被引：1，自引：1，他引：0       下载免费PDF全文

张晨  张双喜  E. Carminati  高冰玉 《地球物理学报》2014,57(10):3208-3217

本文利用有限差分方法,计算了全地幔对流模式和双层地幔对流模式下日本海沟俯冲带热结构、浮力及P波速度异常分布,基于亚稳态橄榄石相变模型推测亚稳态橄榄石的存在范围,同时分析了热传导系数、热膨胀系数和热源对俯冲带热结构的影响,以及俯冲带所受浮力与俯冲带形态的关系.结果表明,双层地幔对流模式下模拟的P波速度异常分布与层析成像结果更为相符,也与深源地震的分布有较好的相关性.板块内部亚稳态橄榄石的存在范围随热传导系数和热膨胀系数的减小而增大,同时忽略相变潜热和剪切生热的影响也会造成模型所预测的亚稳态橄榄石范围偏大.俯冲带所受负浮力在400 km深度附近达到最大值,亚稳态橄榄石的存在使负浮力逐渐减小,甚至在板块内部产生正浮力,不利于俯冲带穿透660 km相变界面.  相似文献   

Provenance discrimination and Source-to-Sink studies from a dryland fluvial regime： An example from Kachchh,western India     

S. P. PRIZOMWALA  Nilesh BHATT  N. BASAVAIAH 《国际泥沙研究》2014,29(1):99-109

Tracing the sediment delivery from its source terrain to its ultimate sink envisage multiple factors that play a vital role in understanding present day erosional engine.To accomplish this,it is significant to distinguish the variable end-members contributing to the basin.The findings from the study of dryland coastal fluvial regime in Kachchh(Western India),which is one of the end members contributing to the Gulf of Kachchh coast(partial sink) and finally to the Arabian Sea(ultimate sink) have been presented here.Multi-proxy sediment provenance proxies such as grain-size,clay minerals,geochemistry and magnetic minerals have been employed to evaluate the provenance discriminating characteristics of the Kachchh dryland fluvial system and factors influencing them.The results of different proxies indicate that the provenance signatures of uplands are quite characteristic with magnetic susceptibility(χ) values of 20×10~(-7)m~3kg~(-1) and smectite(S)/kaolinite(K) ratio between 0.26 and 0.49.The middle reaches show marked increase in magnetic mineral concentration with χ values(140×10~(-7)m~3kg~(-1))and S/K ratio(4.92),while the estuarine tract shows χ values(80×10~(-7)m~3kg~(-1)),S/K ratio(1.90) and,characteristic heavy minerals(i.e.mica minerals),probably reflect the interplay between land and sea oscillations.Major sources of sediments within catchment scale were identified,viz.,upland sedimentary rocks(Juran and Bhuj Formation sandstone-shale) and middle reaches volcanic(Deccan Trap Formation basalt) rocks.The present study draw cautions in provenance of sediment discrimination in areas influenced by Deccan basalt that has the overwhelming sediment delivery and a comparatively subdued effects of other provenance signatures.The studied proxies of mineralogy of clays,magnetic minerals and geochemistry of heavy and major elements serve as the potential for fingerprint of sediment source regions and hence behold a strong position in source to sink studies globally.  相似文献   

一株产铁载体细菌的筛选及其与云母的相互作用   总被引：2，自引：0，他引：2  

何琳燕  张垠  盛下放  黄智 《高校地质学报》2012,18(1):117-124

        产铁载体细菌与云母类矿物相互作用的研究有助于了解矿物生物风化和土壤形成的演化规律和机理。采用纯培养法 自南京龙山废钾矿区酸模根际土壤分离筛选到一株高产荧光铁载体的细菌Z6,通过16S rDNA 序列分析和生理生化反应将其 鉴定为假单胞菌属（Pseudomonas sp.）;通过室温静置培养试验研究Z6 菌株与云母的相互作用结果表明,细菌生长代谢前期 （8~15 d）快速产生大量铁载体,菌株与矿物共培养75 d 后,产铁载体细菌对云母类矿物确实产生了风化作用,黑云母组发 酵液中Fe 含量增加了211 倍,Si 含量增加了约27.8 倍,SEM 显示云母表面出现溶蚀坑,细菌可以在矿物表面形成生物膜或 矿物- 细菌复合物。不同矿物对共培养体系中细菌数量、荧光铁载体含量、溶液pH 的影响不同。  相似文献   

新疆塔城地区黄土沉积的磁学特征及其对古环境变化的指示   总被引：1，自引：0，他引：1  

李冠华  夏敦胜  赵爽  刘现彬  贾佳  魏海涛 《中国沙漠》2012,32(6):1565-1575

西风区黄土沉积序列的磁化率变化特征比较复杂,磁化率与成壤强度之间的相关性在不同的区域环境中具有一定的差异。选取塔城地区黄土剖面作为研究对象进行较为系统的磁学特征分析。结果显示,塔城剖面的磁性矿物主要为磁铁矿、磁赤铁矿等亚铁磁性矿物,同时含有一定量的反铁磁性矿物和顺磁性矿物,磁畴状态主要是多畴（MD）和假单畴（PSD）。成壤作用影响单畴（SD）颗粒磁性矿物的相对含量,而对超顺磁（SP）颗粒的贡献有限。影响地层磁学性质的因素比较复杂,粒度与磁学参数的变化与区域的气候波动具有一定的对应关系。古土壤中磁性矿物浓度的降低以及钙积现象可能反映了成壤时期温暖干燥的气候条件,磁性矿物浓度的变化在一定程度上或许是对区域相对湿度状况的反映。  相似文献   

Thermal equation of state of magnesite to 32 GPa and 2073 K     

Konstantin D. Litasov  Yingwei Fei  Eiji Ohtani  Takahiro Kuribayashi  Kenichi Funakoshi 《Physics of the Earth and Planetary Interiors》2008,168(3-4):191-203

Pressure–volume–temperature relations have been measured to 32 GPa and 2073 K for natural magnesite (Mg_0.975Fe_0.015Mn_0.006Ca_0.004CO₃) using synchrotron X-ray diffraction with a multianvil apparatus at the SPring-8 facility. A least-squares fit of the room-temperature compression data to a third-order Birch–Murnaghan equation of state (EOS) yielded K₀ = 97.1 ± 0.5 GPa and K′ = 5.44 ± 0.07, with fixed V₀ = 279.55 ± 0.02 Å³. Further analysis of the high-temperature compression data yielded the temperature derivative of the bulk modulus (∂K_T/∂T)_P = −0.013 ± 0.001 GPa/K and zero-pressure thermal expansion α = a₀ + a₁T with a₀ = 4.03 (7) × 10⁻⁵ K⁻¹ and a₁ = 0.49 (10) × 10⁻⁸ K⁻². The Anderson–Grüneisen parameter is estimated to be δ_T = 3.3. The analysis of axial compressibility and thermal expansivity indicates that the c-axis is over three times more compressible (K_Tc = 47 ± 1 GPa) than the a-axis (K_Tc = 157 ± 1 GPa), whereas the thermal expansion of the c-axis (a₀ = 6.8 (2) × 10⁻⁵ K⁻¹ and a₁ = 2.2 (4) × 10⁻⁸ K⁻²) is greater than that of the a-axis (a₀ = 2.7 (4) × 10⁻⁵ K⁻¹ and a₁ = −0.2 (2) × 10⁻⁸ K⁻²). The present thermal EOS enables us to accurately calculate the density of magnesite to the deep mantle conditions. Decarbonation of a subducting oceanic crust containing 2 wt.% magnesite would result in a 0.6% density reduction at 30 GPa and 1273 K. Using the new EOS parameters we performed thermodynamic calculations for magnesite decarbonation reactions at pressures to 20 GPa. We also estimated stability of magnesite-bearing assemblages in the lower mantle.  相似文献   

铊矿物晶体化学和地球化学     

范裕  周涛发  袁峰 《吉林大学学报(地球科学版)》2005,35(3):284-290

对世界上已经发现报道的56个铊矿物种类、晶体化学和地球化学特征以及铊矿物产出的地质条件进行了系统总结。将铊矿物分为硫化物、氧化物和含氧盐等六大类,其中铊硫化物矿物占绝大多数。在低温还原环境下,铊表现出强烈的亲硫性,可以与As、Sb、Pb、Hg、Cu和Au等元素结合形成两种形式的铊硫化物矿物：①Tl_wB_yS_z（铊作为唯一的金属元素）,②Tl_wA_xB_yS_z（除了铊以外还有其他的金属元素）。低温成矿域中贱金属矿床是铊矿物的主要产出场所。对目前铊矿物学研究的现状、最新进展和存在的问题进行了综述和探讨。  相似文献   

吉黑东部花岗岩类的副矿物组合特征   总被引：1，自引：1，他引：0  

李俊杰 《地质与资源》2005,14(1):8-11

吉黑东部花岗岩类分布广泛,形成历史漫长,岩石类型齐全.按成因类型划分,以I型为主,A型次之,S型较少,M型极少.各类型花岗岩副矿物组成具有明显特点,因此可以利用副矿物和其组合特征作为划分花岗岩成因类型的判别标志.  相似文献   

西藏纳木错晚更新世以来湖面变化和湖相沉积中粘土矿物显示的环境信息   总被引：13，自引：1，他引：12  

朱大岗  孟宪刚  赵希涛  邵兆刚  马志邦  杨朝斌  王建平  吴中海 《地质力学学报》2004,10(4):300-309

通过对西藏海拔最高、面积最大湖泊-纳木错周缘湖相沉积、湖岸堤的野外调查和湖岸阶地的水准测量,发现在纳木错沿岸拔湖48m以下,发育有6级湖岸阶地,拔湖48~139.2m发育有高位湖相沉积。湖相沉积物的同位素测年结果表明,纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段:①116~37kaB.P.间的古大湖期;②37~30kaB.P.间的外流湖期;③30kaB.P.以来的纳木错期。根据纳木错晚更新世以来湖相沉积中粘土矿物的X光衍射分析结果,以及采用比值法、高岭石法和衍射峰法的研究,探讨了粘土矿物所显示的环境变化信息。粘土矿物成分变化表明,该区已具备了寒温带干旱、半干旱区的气候环境特征。为研究青藏高原的湖泊演化、气候变化、古地理变迁及其隆升过程等提供了新资料。   相似文献