Oxygen and Carbon Isotopes of Cold-water Corals—Reconstructing Paleotemperature Changes and Calcification Mechanism     

Le Kong  Enqing Huang  Jun Tian 《地球科学进展》2019,34(12):1252-1261

Cold-water corals represent an intriguing paleoceanographic archive with a great potential to reconstruct high-resolution paleoenvironmental changes. Compared to those of shallow-water corals, proxies derived from cold-water corals have been complicated by biologically mediated vital effects. The oxygen and carbon stable isotope compositions of cold-water coral skeletons are more depleted than the expected carbonate-seawater equilibrium values by 4‰~6‰ and about 10‰, respectively. Therefore, it is necessary to correct for the vital effects before using δ¹⁸O as a temperature proxy. The principles and methods of reconstructing paleotemperature variations of intermediate and deep oceans using oxygen and carbon isotopes of cold-water corals are reviewed, as well as three existing cold-water coral calcification models and their advantages and disadvantages. It is suggested that further micro-scales analysis and targeted experiments are required to clarify the calcification processes of cold-water corals.  相似文献   

Multi-scale Characteristics and Comprehensive Evaluation of Precipitation Heterogeneity in Guangxi     

Xinchang Xie  Yunchuan Yang  Yi Tian  Liping Liao  Junpei Wei  Jinyu Zhou  Lihua Chen 《地球科学进展》2019,34(11):1152-1164

Aiming at the uneven spatial and temporal distribution of precipitation and frequent occurrence of drought and waterlogging disasters in Guangxi, the multi-scale characteristics and comprehensive evaluation of precipitation heterogeneity can provide scientific support for regional response to drought and waterlogging disasters and intelligent management of water resources. Based on the daily precipitation data of 87 grid points from 1961 to 2017 in Guangxi, the Precipitation Concentration Degree (PCD) and Precipitation Concentration Period (PCP) index were used to build day, pentad, ten days, month, season precipitation heterogeneity of multiple time scale level evaluation system. By using R/S analysis and geographical spatial analysis methods, the space-time evolution characteristics and climate division in Guangxi were discussed. The study showed that the spatial and temporal variation characteristics of PCD and PCP at the diurnal, synoptic and monthly scales were relatively consistent, and the heterogeneity of precipitation in Guangxi could be better expressed than that at the monthly and seasonal scales. The diachronic change of PCD in precipitation in Guangxi shows an increasing trend in northeast China and a decreasing trend in southwest China, and the trend of its future period is the same as the diachronic evolution. The spatial distribution of PCD in Guangxi has significant spatial autocorrelation and stratification heterogeneity, which are mainly reflected in the mean value, coefficient of variation and frequency of PCD. The comprehensive heterogeneity of precipitation in Guangxi is highly dispersed in the northeast, highly concentrated in the south, and slightly concentrated or dispersed in the northwest and central regions. The time-scale within a month is the best scale to express the non-uniformity of precipitation in Guangxi. If the advantages of more stable climatic and ten-day scales and more fine daily scales are taken into account, the use of climatic scale for daily sliding calculation and analysis will be the best way.  相似文献   

凡口铅锌矿狮岭南深部矿床地质特征及找矿方向     

原桂强  贾会业  宋玉伟 《江苏地质》2019,43(1):1-7

广东韶关凡口铅锌矿狮岭南区段的开拓工程已延伸至-550m中段,矿体呈现尖灭趋势。为查明深部区域地层矿化特征、构造控矿特点,并指导深部寻找盲矿体,通过收集分析中上部各中段地质资料,并与地质勘查资料对比,利用坑道设计并施工了9个孔深300 m左右的坑内探矿钻孔,进一步查明了狮岭南深部地质特征,并在F3断裂下盘探获多条盲矿体。F3断裂既是导矿构造,也是重要控矿构造,其下盘至F203断裂之间的夹持带为狮岭南深部有利成矿空间  相似文献   

南海北部珠江口盆地中段伸展构造模型及其动力学   总被引：1，自引：0，他引：1  

漆家福  吴景富  马兵山  全志臻  能源 《地学前缘》2019,26(2):203-221

位于南海北部大陆边缘上的珠江口盆地发育NNE向、NE向、NW向、近EW向等多组基底断裂,盆地结构复杂,并表现出明显的时空差异性。本文基于珠江口盆地中段地震资料解释的构造样式的变化推断地壳中存在一条向南缓倾斜、呈坡坪式形态的拆离断层,古近系构造属于这条拆离断层上盘的伸展构造系统。北部的西江凹陷属于拆离断层伸展构造系统的头部,凹陷边界正断层铲式断层面形态向深层延伸并收敛在拆离断层面上,凹陷表现为半地堑“断陷”样式;中部的番禺低隆起对应于拆离断层的低角度断坪部位,拆离断层上盘断块的伸展位移导致两侧的恩平组超覆在低隆起上;南部的白云凹陷位于拆离断层的深部断坡部位,充填的文昌组和恩平组表现为“断坳”或“坳断”样式;南部隆起位于拆离断层深部断坪部位,其上盘发育的分支断层控制着荔湾凹陷古近系、新近系的发育并使之表现为复杂的断陷断坳构造样式。该模型强调拆离断层上盘与下盘、不同地壳结构层均发生不同程度的伸展变形,且伸展变形方式、应变量等存在时空差异,而拆离断层正是不同构造单元、不同地壳构造层之间的调节性构造面。总体上,拆离断层上盘以脆性伸展构造变形为主,分支断层控制不同构造单元古近纪的构造演化,下盘则是以韧性伸展变形为主,并拖曳上盘发生不均一的伸展应变;西江凹陷的伸展应变量大于拆离断层下盘的伸展应变量,白云凹陷的伸展应变量则小于拆离断层下盘的伸展应变量。以西江凹陷北部边缘的NE向铲式正断层为头部的拆离断层控制了文昌组沉积,但在恩平组沉积期被近EW向高角度正断层切割破坏而被遗弃,拆离断层系统的头部由西江凹陷北部边缘迁移至番禺低隆起。盆地结构及断裂系统的时空差异性受盆地基底先存构造、地壳与岩石圈结构及伸展量等多方面因素的影响,但主要是对软流圈流动及岩石圈热结构变化的响应。用软流圈由北西向南东流动拖曳上覆岩石圈发生伸展变形的动力学模型能合理地解释珠江口盆地中段古近系构造的形成和演化。  相似文献   

基于离散元方法对走滑拉分盆地演化及次级断裂扩展过程研究     

刘源  KONIETZKY Heinz 《地质力学学报》2019,25(5):840-852

拉分盆地是一种与走滑断裂带密切相关的特殊拉张构造,因其重要的构造意义,及其与火山活动、中小地震群集、特殊的成矿作用间的伴生关系而受到研究者的高度重视。关于拉分盆地的形成演化过程,已有较多的研究成果,但是由于研究手段的限制,缺少对盆地演化中次级断裂扩展过程的研究。基于离散元的数值计算方法是研究断裂扩展方式的理想方法。本文采用基于离散元的颗粒流方法,揭示纯走滑拉分盆地发育过程中的断裂扩展和连接过程,为拉分盆地演化机理和断裂扩展提供新的研究方法。同时,根据主走滑断层与块体运动方向的夹角不同,建立不同的张扭性拉分盆地模型,系统研究张扭性盆地的断裂扩展和演化机理。将上述理论研究结果与死海盆地等经典拉分盆地实例相结合,探讨了死海盆地、土耳其Cinarcik盆地、哥伦比亚El Paraiso盆地等的形成演化机理和断裂扩展方式。   相似文献   

初论雪峰山地区基性-超基性岩镍钴铜金矿找矿方向     

石少华  邹源  岑敏  朱继华  罗小亚 《矿物岩石地球化学通报》2019,(1):80-89

近年来,雪峰山地区的基性-超基性岩矿床找矿工作取得了一定的进展。为了及时总结成矿规律,指导进一步的找矿工作,本文在大量野外调研的基础上,系统总结了该地区基性-超基性岩岩体的地质特征、已有找矿进展的长界镍矿和字溪金矿地质特征及已发现的镍钴铜金等矿化特征,并与国内外同类型矿床的成矿特征进行了比较,最后提出了如下认识:雪峰山地区具备找寻基性-超基性岩矿床潜力,目标矿种主要为镍、钴、铜及金矿,主要矿床类型为岩浆硫化物型镍钴铜矿及蚀变热液型金矿。前者目标地质体以通道-洪江-中方-古丈一带新元古代基性-超基性岩群/带最为有利,后者则以隘口岩群及艾头坪-大洪山岩群的大洪山段最为有利。  相似文献   

鄂尔多斯盆地渭北地区上三叠统延长组长7油层组碳酸盐结核中自生碳酸盐矿物的特征          下载免费PDF全文

李云  胡作维  刘灿  董杰  贺静  袁效奇  魏杨 《古地理学报》2019,21(4):577-588

早期形成的碳酸盐结核在埋藏期间会经历多种碳酸盐矿物相沉淀的复杂胶结作用,岩石学研究是探究结核成因的关键。通过野外剖面观察、岩石学观察和阴极发光技术,分析了鄂尔多斯盆地渭北地区上三叠统延长组长7油层组泥页岩中各种形状的方解石和白云石结核中自生碳酸盐矿物的特征。这些结核为成岩早期的产物,构成结核的自生碳酸盐矿物特征显著:(1)球粒方解石结核中,方解石呈纤维状或刃片状,球粒间充填晶粒方解石或因压实呈贴面结合,纤维状方解石发桔红色和暗红色2种光,刃片状方解石发暗红色光;(2)粉晶方解石结核中,方解石呈他形粒状,含有机质包裹体或纤维状晶形残余,晶间含沥青和纤维状方解石残余,主要发暗红色光;(3)白云石结核有泥晶和粉晶2种晶体类型,粉晶白云石结核含较多泥质,泥质条带或有机质条带处常见纤柱状白云石;(4)沿裂缝充填的方解石和白云石常呈纤维状或纤柱状结构,发暗红色光或不发光。研究区长7油层组碳酸盐结核中的方解石和白云石具有不同的成因类型和复杂的胶结作用:球粒方解石和泥晶白云石代表了结核开始形成时的胶结作用,可以准确地反映结核的成因;粉晶方解石、粉晶白云石反映了交代成因;裂缝中纤维状、纤柱状方解石和白云石集合体则为结核经历了较强压实作用之后充填裂缝而成。  相似文献   

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

Yue‐Heng Yang  Fu‐Yuan Wu  Qiu‐Li Li  Yamirka Rojas‐Agramonte  Jin‐Hui Yang  Yang Li  Qian Ma  Lie‐Wen Xie  Chao Huang  Hong‐Rui Fan  Zi‐Fu Zhao  Cheng Xu 《Geostandards and Geoanalytical Research》2019,43(4):543-565

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.  相似文献   

新疆东昆仑西段库拉甫河岩组火山岩地球化学特征及锆石U-Pb年龄     

周能武  陈邦学  杨有生  郭新成  朱志新  陈甜  白权金 《地质通报》2019,38(5):757-766

对东昆仑西段库拉甫河岩组火山岩地球化学进行研究,结果显示,主量元素MgO、FeO含量较高,TiO_2和K_2O含量分别为1.12%、0.63%,与岛弧拉斑玄武岩(0.84%、0.43%)接近;微量元素具有Sr富集,高场强元素Nb、Ta略亏损,P无明显分馏或未分馏的特征,稀土元素球粒陨石标准化配分曲线显示良好的同源性(配分曲线变化规律近似一致),且与富集型洋脊玄武岩配分趋势一致。结合构造环境判别,认为其形成于岛弧环境,具有岛弧拉斑玄武岩的特征,来源于与岛弧相关的富集地幔。利用锆石U-Pb测年获得2组年龄,其中一组年龄为688.7±5.1Ma,代表捕获晶年龄,另一组年龄483.4±3.3Ma为结晶年龄,代表玄武岩的形成年龄,属于早奥陶世。结合其构造环境、岩石地球化学特征和年龄数据,认为其是原特提斯洋俯冲消减环境下的产物,且原特提斯洋俯冲至少持续到早奥陶世。  相似文献   

基于LAHARZ的泥石流堆积范围预测模型的建立及应用     

王常明  李桐  田书文  李硕 《吉林大学学报(地球科学版)》2019,49(6):1672-1679

为了探究泥石流的堆积范围,利用LAHARZ软件,对北京市密云县泥石流沟喇嘛栅子南沟进行了数值模拟。结合泥石流沟小流域1：10 000数字高程模型图,模拟了泥石流的堆积范围。首先利用中国部分地区泥石流体积和堆积范围的数据资料,获得了泥石流体体积与其堆积范围的新的统计模型B=11.42V^0.7156;然后通过模拟沟道与实际沟道的对比,确定了最佳沟道阈值为15 000;再结合现场调查统计和降雨历史资料,确定了10年、20年、50年和100年一遇暴雨条件的泥石流体积值,分别为56 500、72 900、94 200和113 100 m³;最后在此基础上对该条泥石流沟的堆积范围进行了预测。结果表明,100年一遇的暴雨条件下泥石流堆积面积为48 729 m²,到达最远距离约为490 m,已影响下游村庄。  相似文献