Sequence architecture and depositional evolution of the Ordovician carbonate platform margins in the Tarim Basin and its response to tectonism and sea‐level change

The sequence architecture and depositional evolution of the Ordovician carbonate platform margins in the Tarim Basin, China, were formed in response to the interplay of tectonism and sea‐level change, their history being documented by the integrated analysis of many seismic lines, drilling and outcrop data. The Ordovician carbonate system in the basin is divided into four composite sequences defined by major unconformities. Each sequence consists of a regional depositional cycle from transgression with an onlapping transgressive systems tract (TST) to regression with a prograding highstand systems tract (HST), and can be further subdivided into 10 third‐order sequences based on subordinate discontinuous boundaries at the carbonate platform marginal zones. Constrained by the marginal slope of the early‐rifted Manjiaer aulacogen, the carbonate platform margins of the Lower and Middle Ordovician that prograded eastward in an arcuate belt extending generally north‐south across the northern part of the basin. The development of the Tazhong uplift due to compression resulted in an extensive paleokarst hiatus between the Middle and the Upper Ordovician in the south‐central basin, and subsequently constrained the formation of a peninsula‐shaped carbonate platform whose margins were controlled by marginal thrust‐fault belts of the paleo‐uplift during the Late Ordovician. In the northern basin, the Late Ordovician carbonate platform margin developed around the marginal slope of the Tabei paleouplift. The transgressive–regressive cycles of the carbonate system are comparable and seem to have occurred simultaneously across the entire basin, suggesting that the cyclic sequence architecture was fundamentally controlled by eustatic fluctuations. Stacking patterns of the composite sequences varied due to the interplay between the accommodation produced by tectonism and sea‐level change, and the carbonate production rate. The reef–shoal facies complexes that developed along the platform margins, with paleokarst development at unconformities, constitute the major reservoir of large petroleum reserves in the basin.     

腾格里沙漠东南缘不同年代固沙区根系分布

2010年8月,选择腾格里沙漠东南缘1964年、1981年和1990年建立的人工固沙区为对象,以流动沙丘和邻近的天然植被区为对照,利用根钻取样法研究了不同年代固沙植被区根系的3.0 m剖面的分布特征。结果表明：单位土地面积上<1 mm的活根、全部活根、<1 mm的死根和全部死根的重量密度和长度密度在不同样地间存在着显著差异(p<0.05);流沙、1990年、1981年、1964年固沙区和天然植被区全部活根重量密度分别为2.9±2.2、164.7±46.5、461.3±83.6、440.4±81.8 g·m-2和350.0±132.5 g·m-2,5个样地全部死根重量密度分别为4.9±2.8、58.7±16.8、390.9±57.9、492.5±252.2 g·m-2和214.4±29.9 g·m-2;根长密度也表现为相似的变化趋势。单位土壤体积的根系重量密度和长度密度随着土层加深而递减,植被区0~1.0 m土壤层活根的累积重量密度和长度密度在全部活根中的比例均超过70.0%,其中以天然植被区最大,流沙区则不超过25%;死根也表现为相似的趋势,只是比例有所降低。根鞘占全部根系生物量的比例非常不稳定,流沙区的最大,为94.3%,而1981年植被区的只有0.5%,1964年、1990年固沙区和天然植被区分别为29.9%,70.3%和58.9%。     

黄河流域煤炭富集区煤炭水足迹演变及驱动效应研究

煤炭与水资源相互影响和制约,如何评价煤炭耗水的演变趋势及其影响机制对煤炭和水资源进行协同管理具有重要意义。基于国际标准的煤炭水足迹测算模型,分析2000—2017年黄河流域煤炭富集区——晋陕蒙煤炭水足迹的时空演变趋势,构建煤炭水足迹压力指数评价区域煤炭和水资源的匹配关系,并运用LMDI模型定量分析煤炭水足迹的驱动效应。结论如下：① 煤炭水足迹总量在研究期内呈增长趋势,主要以原煤和火力发电水足迹为主,山西和内蒙古煤炭水足迹最高,陕西最低。② 研究区整体煤炭水足迹压力指数逐渐增大,由煤–水关系缓和型逐渐演变为煤–水关系制约型,从空间分异来看,山西最大,研究期内均属于煤–水紧张型,陕西次之,内蒙古最小,均由煤–水关系缓和型演变为煤–水关系制约型。③ 影响煤炭水足迹的主要驱动因素是经济效应和技术效应,前者对煤炭水足迹的影响逐渐增强,后者对煤炭水足迹压力的影响先增强后减弱,各驱动效应空间分异明显。研究结果可为煤炭富集区煤炭和水资源可持续利用提供决策参考,为黄河流域生态保护和高质量发展的资源管理提供决策支持。     

斜纤蛇纹石的管道水特征研究

河北涞源斜纤蛇纹石为较小的中孔纳米管材料,通过氮吸脱附法、差热和热重曲线分析法、差示扫描量热分析法和红外光谱分析法,主要分析了其纳米管中管道水特征,明确了管道水作为有效加速剂和载体的作用,对以及对抗拉强度和介电常数的影响。研究表明斜纤蛇纹石纳米管中存在管道水(属于吸附水),去除温度在240℃±,内径为2nm～3nm的纳米管中管道水含量最高,管道水含量与纳米管分散度成反比。     

西秦岭太阳山斑岩铜-钼矿床岩体氧逸度及成矿意义

甘肃天水三叠纪太阳山斑岩铜钼矿床位于西秦岭造山带东段。矿体主要赋存于石英闪长斑岩、二长斑岩、石英二长斑岩和泥盆系大草滩群。氧逸度是表征岩石物理化学性质的重要参数,对岩浆热液成矿具有明显的控制作用。在综合评述常用氧逸度计算方法及适用性的前提下,文中应用激光剥蚀等离子质谱分析方法对太阳山矿床含矿岩体锆石微量元素进行测定,选用含量较高的Sm、Nd进行Ce异常计算,查明含矿斑岩岩浆氧逸度,探讨其成矿意义。太阳山矿床岩浆氧逸度计算结果表明,太阳山成矿二长斑岩和石英二长斑岩相对氧逸度ΔFMQ分别为+3.04和+3.15,成矿前石英闪长斑岩相对氧逸度ΔFMQ为-1.83,成矿岩体氧逸度明显高于成矿前岩体。成矿岩体岩浆氧逸度高于成矿前岩体的原因可能与富集地幔有关。富集岩石圈地幔的加入,带来了大量的硫和金属铜,并提高了岩浆氧逸度。     

多年冻土地基正温输气管道地温场实测及分析

我国有多条油气管道位于多年冻土地区,工程问题层出不穷。因输送介质处于正温状态,其所释放热量对管道周围冻土冻融过程有极大影响。为阐明正温管道对多年冻土温度场及冻融特征的影响,基于西部某多年冻土区正温输气管道现场实验,对管道地基温度场进行了为期1年的现场实测。数据分析表明,多年冻土天然上限为1.5~2.0 m;土体融化期及冻结期分别为6-10月、11-次年5月;监测段多年冻土热量收支基本平衡,属于不稳定冻土,在外界热扰动下极易退化;正温输气管道的存在引起了多年冻土的退化且对其温度场有很大影响,水平方向影响范围约1.5 m,管下最大融深可达7.0 m。同时指出了针对处于临界状态的多年冻土,在基于对其全面、深入了解的基础上,越早考虑相关工程建设带来的热扰动对多年冻土的不利影响,则处置难度越低且损失越小。     

In Situ U‐Th‐Pb Dating and Sr‐Nd Isotope Analysis of Bastnäsite by LA‐(MC)‐ICP‐MS

Bastnäsite is the end member of a large group of carbonate–fluoride minerals with the common formula (REE) CO₃F·CaCO₃. This group is generally widespread and, despite never occurring in large quantities, represents the major economic light rare earth element (LREE) mineral in deposits related to carbonatite and alkaline intrusions. Since bastnäsite is easily altered and commonly contains inclusions of earlier‐crystallised minerals, in situ analysis is considered the most suitable method to measure its U‐Th‐Pb and Sr‐Nd isotopic compositions. Electron probe microanalysis and laser ablation (multi‐collector) inductively coupled plasma‐mass spectrometry of forty‐six bastnäsite samples from LREE deposits in China, Pakistan, Sweden, Mongolia, USA, Malawi and Madagascar indicate that this mineral typically has high Th and LREE and moderate U and Sr contents. Analysis of an in‐house bastnäsite reference material (K‐9) demonstrated that precise and accurate U‐Th‐Pb ages could be obtained after common Pb correction. Moreover, the Th‐Pb age with its high precision is preferable to the U‐Pb age because most bastnäsites have relatively high Th rather than U contents. These results will have significant implications for understanding the genesis of endogenous ore deposits and formation processes related to metallogenic geochronology research.     

黄土高原风成沉积物磁化率各向异性研究

中国黄土高原粉尘堆积以往注重从物源区携带粉尘的古风向,对粉尘沉积→固结期的古风向缺乏研究。本文评述了近年来应用黄土高原黄土、红粘土磁化率各向异性研究古季风风向变迁所取得的一些重要进展并指出磁化率各向异性最大轴和最小轴的方位和倾伏均与沉积→固结期风向变化密切相关。黄土磁组构结果与利用各种统计方法计算出的古风向在多个剖面与现代夏季风方向相似,由此推论黄土是冬季风带来的沙尘在经历夏季风携带的降雨洗礼后才固结而成。而在黄土之下的红粘土地层中的初步研究发现磁组构显示明显的西风带沉积特征,指出这一现象将在今后研究中继续深入探讨。     

岩石应力-应变过程中渗透率变化分析

岩石空隙率与空隙的几何性质是影响其渗透率的关键因素。通过分析渗透率-应变曲线与岩石破坏过程的对应关系,指出岩石的渗透率与岩石的体应变密切相关。在压密区间内,岩石的渗透率呈现为负指数下降;峰前膨胀区间内,渗透率快速增加,并在末期形成贯通性的渗透通道;在峰后阶段由于部分通道被堵塞,渗透率发生下降。同时,将断裂力学推广到考虑岩石介质的微观破坏不均匀性,指出岩石渗透率的变化主要是由尺度等级较小的微破裂的相互作用和生长引起的主干断裂,进而形成贯通性的渗透通道。     

萃取分离—石墨炉原子吸收光谱法测定铅锌矿中的铟

样品经硝酸、氢氟酸分解除硅,加热硫酸冒烟除尽硝酸、氢氟酸,利用铟与氢溴酸能生成稳定的络合物并被乙酸丁酯萃取的性质,将铟与其它干扰离子分离并富集.使用MOLAARM6（Thermo Electron Corporation）石墨炉原子吸收分光光度计,以钒为机体改进剂,测定铅锌矿中的铟.方法检出限为LD=0.012ug/ml.实验结果令人满意.