Luminescence chronology of ＂Old Red Sand＂ in Jinjiang and its implications for optical dating of sediments in South China

A weathered deposit in South China is widespread on the coastal areas of Fujian and Guangdong provinces, China. This deposit consists of slightly cemented, medium- to fine-grained sands, and is characterized by its colors of red, brown red, light reddish brown or dark yellowish orange, and is usually called ＂Old Red Sand＂. The uncertainty in its formation age has been a major obstacle to the study of this type of deposit. In this paper, optically stimulated luminescence （OSL） techniques were used to date the ＂Old Red Sand＂ sediments from Jinjiang, Fujian Province, China. The effect of the geochemical behavior of uranium and thorium in sediment during chemical weathering on estimation of annual dose was investigated. The results show that the change in annual dose due to weathering poses a major problem for the optical dating of such weathered sediments. The optical dating of these weathered deposits will produce erroneous ages if average annual dose during burial cannot be correctly estimated. For the profiles studied, the OSL dates obtained on samples from the upper part do not represent the burial age of the samples. It is highly likely that they are underestimated due mainly to the accumulated radioactive elements as a result of chemical weathering. It is concluded that changes in annual dose due to chemical weathering must be considered when dating similar sediments in South China. With a detailed analysis of the OSL dating results, the chronology of the marine terraces in this area was suggested. The lowest terrace was formed at -3.5 ka and the second terrace was dated to -74 ka. The age of the highest terrace may not be established accurately, but is inferred to be older than the apparent OSL date of -77 ka and so is the Paleolithic artifacts from it.     

Chronology of the stratum containing the skull of the Dali Man

The field investigations of geomorphology and Quaternary sediment sequences show that the sediment stratigraphic profile containing the skull of the Homo sapiens Daliensis (Dali Man) at Tianshuigou trench, Jiefang Village (109° 44′E, 34°52′N), Dali County, Shaanxi Province, is composed of the loess-paleosol sequence, 17.3 m thick, in the upper part, and the alluvial silts, fine sands and sandy gravels interbedded, 15.4 m thick, in the lower part. There are the well developed layers L₁, S₁, L₂ and S₂ in the loess-paleosol sequence of the profile, which are comparable; to those of the Luochuan loess section on the basis of magnetic succeptibility measurements and IRSL dating of the loess samples. An alluvial gravel layer, where the skull of the Dali Man was discovered, is in 13 m beneath the bottom of paleosol S₂, implying that, the age of the Dali Man must be older than about 247 kaBP when the paleosol S₂ began to be developed. The samples of mammal animal tooth and shell fossils from the gravel layer containing the skull of the Dali Man have been dated by uranium series and ESR methods respectively. Based on the multiple dating results and the stratigraphic chronology, the age of the Dali Man, therefore, would be estimated as older than 250 kaBP and younger than 350 kaBP, and reasonably estimated as 260–300 kaBP.     

High-precision uranium-series dating of lacustrine carbonates from Daihai Lake

Ages of small aragonite samples retrieved from sediments from the Daihai Lake are determined by using the Thermal Ionization Mass Spectrometry (TIMS) technique. The ages of the samples range from (8740±601) to (10446 ±489) a, with a precision of 2%–3% for non-corrected dating ages and 4.7%-9.8% for corrected ages respectively, and are consistent within the deviation range. At about 10.5 ka BP, the grain-size of the sediments coarsens sharply, the frequency curves of grain-size distribution show coarse grain dominated single-double kurtosis, indicating cooling, decreased hydrodynamic conditions and increased wind influence procedure. This is in good agreement with previous results obtained from the Daihai Lake, which suggests that the climate was cold and the lake surface was shrinking. The TIMS ages of the sediments are therefore believed to be credible.     

Evidence for hydrogen-deuterium exchange in viral particles

Heavy water (D2O) could enhance thermostability of some viruses. However, the underlying mechanism is not clear. Here we report the development of a matrix-aided gas-isotope-ratio mass spectrometry method that allows direct determination of deuterium/hydrogen (D/H) ratio in D2O-treated Japanese encephalitis virus (JEV), hepatitis A virus (HAV) and RNA from D2O-treated HAV. The D/H ratiowas expressed as δDSMOW. Our experiments showed that δDSMOW values increased significantly in D2O-treated viral samples compared to normal controls, and increment in δDSMOW of D2O, treated viral samples was in a fine linear relationship with increment in amount of samples loaded in BSA matrix. Our experiments also indicated that increased δDSMOW of D2O-treated virus correlated well with its enhanced thermostability. The results suggested that hydrogen-deuterium exchange occurred in viral particles and its RNA structure as a result of D2O-treatment. Furthermore,such exchange could cause changes in viral phenotype, such as enhanced thermostability.     

Theoretical investigations of ESR and optical spectra of crystalline KHSO4：Mn^2＋

Calculations of d-d transitions and the axial zero-field splitting parameter D in crystalline KHSO4:Mn2+ have been undertaken, with consideration of the ninth O2– ligand. Energy level values calculated in a tetragonal field are in good agreement with experimentally observed values. Occasionally degenerate energy levels of 4A1(4Eg(G)) and 4A1(4A1g(G)) were found in the tetragonal crystal field. The calculated value of D is in good agreement with experimental value for KHSO4:Mn2+.     

U-series dating on late Quaternary sediments from Balikun Lake

The U-series component-dating method has been employed to date the sediment core B-194 from Balikun Lake. 230Th/ 232Th and 234U/ 232Th ratios in various components of the samples dissolved in different concentration acids were measured respectively. The results indicate that there is a good relationship of the isotopic ratios between the solutions and the residues, and that uranium and thorium isotopic fractionations did not occur during acid leaching. Based on the U-series ages obtained by using component-dating method, a 144-ka time sequence was established corresponding to the upper 25-m interval of the B-194 core, which is in agreement with palaeomagnetic dating results. The fact that the palaeoclimatic and palaeoenvironmental record labeled with U-series ages is correlative with the deep-sea δ 18O SPECMAP also demonstrates that the U-series component-dating method can be used to date lake sediments.     

洛阳二里头遗址南沉积剖面的粒度和磁化率分析

洛阳盆地内二里头遗址南沉积剖面位于遗址所在二级阶地的前缘,属于河流堆积。对剖面的沉积物样品做了光释光测年及磁化率、粒度分析。结果表明:剖面沉积年代大致在2000~5000 aBP之间。剖面下部(113~123 cm)沉积物粒度较细,磁化率偏高,粒度曲线反映水流较弱的泛滥平原沉积环境,属河漫滩堆积;中部(90~113 cm)粒度较粗,磁化率较低,粒度曲线反映水动力较强的边滩–漫滩沉积环境,属河床边滩堆积;上部(0~90 cm)粒度变细,磁化率升高,粒度曲线反映水动力条件较弱的泛滥平原沉积环境,属河漫滩堆积。其中沿水平方向可见剖面中部的河床边滩堆积直接覆盖在二级阶地顶面的龙山时期灰坑之上,由此可以确认剖面中部地层记录了一场漫上了河流阶地的特大洪水事件,这一记录与孢粉分析得到的气候变化过程具有明显的相关性。4000 aBP前后异常洪水的出现和大洪水前后河流过程的变化,可能是对4200 aBP全球性气候异常事件的区域响应,对我国最早的都邑——二里头城址的选址有重要的影响。     

Χ射线激发的光释光测年技术实验研究

】文章提出了利用Χ射线作光释光测年的激发光源，以此进行了实验研究。研究结果表明，利用Χ射线是可以激发辐射样品使其产生光释光信号的     

Late Pleistocene human skull from Jingchuan,Gansu Province

Jingchuan human fossil, found in Gansu Province in 1976, was given a preliminary report in 1984, but questions remained con- cerning the age and character of the fossil. We conducted field investigation at Jingchuan in May of 2006 to examine the stratum yielding the human fossil and to obtain sediment samples for optically stimulated luminescence (OSL) dating. Three samples collected from different stratigraphic levels at the fossil locality yielded OSL dates of 15, 48 and 7.9 thousand years ago (ka), respe...     

双辊薄带连铸1.2%Si无取向电工钢组织和析出物

研究了双辊薄带连铸条件下,1.2%Si无取向电工钢初始组织和析出物形貌及分布规律.结果表明,在1 550℃浇注条件下,铸带经过空冷后以粗大的原始铸态铁素体组织为主,也有一部分相变产生的细小晶粒,晶粒尺寸范围为50~400μm.铸带中析出物为AlN和MnS,其中AlN析出分为高温析出和相变析出两种,高温析出AlN尺寸在0.5μm左右,相变析出AlN尺寸则在100 nm左右,二者对再结晶组织影响不大.MnS在铸带成型和成品退火过程中都有析出,尺寸范围为30~40nm.     

SHRIMP U-Pb dating and Hf isotopic analyses of zircons from the mafic dyke swarms in central Qiangtang area, Northern Tibet

In the ＂Central Uplift＂ of Qiangtang, Northern Tibet, a large scale of mafic dyke swarms extended in E-W direction. Zircon SHRIMP U-Pb dating on two representative samples of diabase dyke yield weighted mean ages of 284 ± 3 Ma and 302 ± 4 Ma, respectively, suggesting they emplaced in the Late Carboniferous to Early Permian. Zircon ^176Hf/^177Hf ratios range from 0.282852 to 0.283041, with ,εHf（t） values of ＋12.1 to ＋12.2 and Hf modal （TDM） ages of ～440-460 Ma. These data indicate that these mafic dykes were mainly derived from the depleted mantle. In addition, geochemical data suggest that these mafic dyke swarms are of intra-plate origin. Therefore, the mafic dyke swarms represent products during the extensional process associated with the opening of the Paleo-Tethys Ocean in the area.     

Thickness of calcium carbonate coats on stones of the Heishanxia terraces of the Yellow River and dating of coarse clastic sedimentary geomorphic surfaces

The calcium carbonate coats on stones developed in soil on the geomorphic surfaces of coarse clastic sediments in arid-semiarid regions contain evident information of age. The thickness of coats can be used not only as a good age indicator for the geomorphic surfaces but also coats themselves can be directly used as dating materials in the ESR method. Through measuring the thickness of carbonate coats on stones in soils on the alluvial terraces in the mouth of the Heishanxia gorge of the Yellow River and ESR dating of layers separated from the carbonate coats, the average of accumulation rates of the thickness of carbonate coats on stones since 1.57 Ma was calculated to be 0.10 mm/ka in the studied area, and a regression equation between carbonate coat thickness and age was also generated. From these research results, ages of T2-T11 terraces of the Yellow River in the studied area were systematically determined, and their values are in turn 18 ka, 94 ka, 139 ka, 215 ka, 305 ka, 410 ka, 495 ka, 742 ka, 1072 ka and 1570 ka. The reliability of all these age data is confirmed by the obtained 14C, OSL ages (T2, T3 and T4) and ESR ages of neighbor terraces, and they are completely consistent with the geological epochs estimated by geological and geomorphologic comparison and analysis.     

Design of a novel optically stimulated luminescent dosimeter using alkaline earth sulfides doped with SrS:Eu,Sm materials

Optically stimulated luminescence （OSL） is the luminescence emitted from an irradiated insulator or semiconductor during exposure to light. The OSL intensity is a function of the dose of radiation absorbed by the sample and thus can be used as the basis of a radiation dosimetry method. Alkaline earth sulfides doped with rare-earth elements such as Ce, Sm and Eu are OSL dosimeters having very high sensitivity, and the OSL with a short time constant is separated from the stimulated light. In this paper, a novel OSL dosimeter designed with SrS：Eu,Sm materials is described. The dosimeter takes advantage of the characteristics of charge trapping materials SrS：Eu,Sm that exhibit OSL. The measuring range of the dosimeter is from 0.01 to 100Gy. The equipment, which is relatively simple and small in size, is promising for applications in space exploration and high dose radiation dosimetry.     

Identification of 3.5 Ga detrital zircons from Yangtze craton in south China and the implication for Archean crust evolution

The LA-ICP-MS U-Pb dating of hundreds of detrital zircon grains from the Sinian sandstones of Liantuo formation and tillites of Nantuo formation at Sanxia area in Yichang identified 3319?3508 Ma zircon grains. Their ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁶Pb/²³⁸U ages show excellent agreement (concordia degree 99%?100%). Their CL images exhibit well-developed oscillatory zoning and the Th/U ratios are within 0.46?0.76, implying that they are igneous zircons which formed during middle-early Archean. These zircons are the oldest ones discovered in Yangtze craton until now. However, the detrital zircons with ages older than 3.3 Ga in the metamorphic rocks of Kongling group were not found by further investigation, which suggests the presence of crust older than high-grade metamorphic Kongling terrain in Yangtze craton.     

应用正交试验法的RHT模型参数敏感性研究

基于RHT模型的理论分析,选出A、N、B、M、B_Q、f_s/f_c、T_ten、D₁和E_f,min 9个参数作为正交试验分析参数,研究RHT模型中参数的敏感性.运用Autodyn程序对弹丸侵彻混凝土过程进行数值分析,确定了不同参数、不同水平值下弹丸的侵彻深度.采用极差分析法对参数的敏感程度进行量化分析,得出9个参数的敏感性排序为B > E_f,min > T_ten > f_s/f_c > N > M > D₁ > B_Q > A.结合3组典型数值试验损伤云图和侵彻深度的对比分析,认为参数B、E_f,min和T_ten对数值模拟试验结果的影响极大,应采取可靠的技术手段准确确定其取值.      

裂变径迹定年资料应用中的问题及其地质意义

裂变径迹定年与其他大多数放射性定年法不同,它测量的是放射性衰变对矿物晶体的物理损伤,而不是另一种同位素。外探测器裂变径迹定年分析中,可以获得每一个颗粒径迹年龄。样品裂变径迹年龄表述有组合年龄、平均年龄和中值年龄,不论哪种年龄都不具有简单的地质意义。封闭径迹长度及分布记录了岩石经历的最高古地温及热历史过程,是裂变径迹分析中最重要的参数。利用裂变径迹参数,可进行热史模拟,以重建样品的热历史。     

Effect of thickness on structures of ultrathin diamond-like carbon films

Diamond-like carbon (DLC) films with different thickness were deposited by filtered cathode vacuum arc (FCVA). Vis-Raman and spectroscopic ellipsometry were employed to analyze the structure of DLC films. The wavelength of Vis-Raman is 514.5 nm. Experimental results show that structures of DLC films are affected by film thicknesses. When the film thickness increases from 2 to 30 nm, the G-peak position (G-pos) shifts to higher wavelength, the intensity ratio I_D/I_G and the extinction coefficient Ks decrease. It is indicated that the content of sp3 bond increases with film thickness. However, when the film thickness increases from 30 nm to 50 nm, I_D/I_G and Ks increase. The content of sp³ bonds decreases with film thickness.     

Opening of the Longmu Co–Shuanghu–Lancangjiang ocean:constraints from plagiogranites

This paper reports new zircon U-Pb ages,and Hf isotope and whole-rock major and trace element data for Cambrian plagiogranites from the Tuobeiling ophiolite in central Qiangtang,Tibetan Plateau.Zircon SIMS and LAICP-MS U-Pb dating of the plagiogranites yield weighted mean ages of 504.8±4.2 and 491.6±1.5 Ma,respectively.The zircons from plagiogranites exhibit positive eHf(t)values(ranging from 11.46 to 15.16),indicating that the plagiogranites are derived from depleted mantle.These plagiogranites are characterized by high SiO2and Na2O,low K2O,low REE contents,and flat REE distribution patterns.These rocks have geochemical compositions typical of oceanic plagiogranite and,considered along with their petrography and field relationships,are interpreted to have derived from anatexis of hydrated amphibolites by ductile shearing during transports of the oceanic crust.The formation age of such type of plagiogranite is slightly younger than that of the associated section of oceanic crust.Thus the new results from these plagiogranites suggest that the Longmu Co–Shuanghu–Lancangjiang ocean had probably opened before the Middle Cambrian.     

A ∼2.5 Ga magmatic event at the northern margin of the Yangtze craton: Evidence from U-Pb dating and Hf isotope analysis of zircons from the Douling Complex in the South Qinling orogen

The poorly studied Douling Complex is a crystalline basement that developed in the Neoproterozoic-Paleozoic weakly metamorphosed to non-metamorphosed strata at the South Qinling tectonic belt. Five banded dioritic-granitic gneiss samples from the Douling Complex were chosen for LA-MC-ICPMS U-Pb zircon dating, which yielded protolith emplacement ages of 2469 ± 22 Ma, 2479 ± 12 Ma, 2497 ± 21 Ma, 2501 ± 17 Ma and 2509 ± 14 Ma, respectively. An important peak age of ～2.48 Ga was also obtained for a metasedimentary rock in the same region. These discoveries suggest the occurrence of magmatic activity of 2.51–2.47 Ga at the northern margin of the Yangtze craton. The age-corrected ? _Hf(t) values obtained from in situ zircon Hf isotopic analysis are mainly between ?5.5 and +0.3, and the two-stage zircon Hf model ages range from 3.30 to 2.95 Ga. Considering two important periods of ～3.3–3.2 Ga and ～2.95–2.90 Ga for the continental crustal growth in the Yangtze craton, we infer that the dioritic-granitic gneisses from the Douling Complex are the products of reworking of Paleo- to Mesoarchean crust at the northern margin of the Yangtze craton at ～2.5 Ga. In addition, metamorphic ages of 837 ± 8 Ma and 818 ± 10 Ma were obtained for zircon overgrowth rims from a dioritic gneiss and a metasedimentary rock, indicating that the main phase amphibolite facies metamorphism of the Doulng Complex occurred during the Neoproterozoic, although its geological meaning remains ambiguous.     

Mesozoic-Cenozoic thermal history of Turpan-Hami Basin: apatite fission track constraints

Apatite fission track dating is carried out on nine samples collected from the central part (Lianmuqin section) and from both northern and southern margins of Turpan-Hami Basin. The fission-track ages of seven Jurassic samples are distinctly younger than depositional ages. In contrast, the fission-track ages of two Cretaceous samples are older than, or as old as depositional ages. These observations indicate that the Jurassic samples have been annealed or partially annealed, whereas the Cretaceous samples have not been annealed.The further thermal modelling results show that Turpan-Hami Basin experienced a Late Cretaceous period (120-100 Ma) of tectonic uplift with rapid cooling and exhumation of sediments. The samples underwent a Cenozoic period of reburial and re-heating and were exhumed again at 10-8 Ma.