北太平洋副热带模态水盐度的年代际变化     

胡睿坤  边志刚  刘子洲  刘聪  翟方国  顾艳镇 《中国海洋大学学报(自然科学版)》2020,(2):9-21

副热带模态水(Subtropical Mode Water;STMW)在气候变化中起着重要作用。本文利用全球高分辨率数值模拟结果,研究了北太平洋STMW核心层盐度(Core Layer Salinity;CLS)的年代际变化及其物理机制。结果表明,CLS存在显著的年代际变化,其空间分布则与背景流场分布特征有关。侵蚀区CLS滞后生成区CLS约1~2年,这主要是海流平流输运引起的。生成区内,STMW的季节循环一般可分为生成期(12-4月)、隔离期(5-6月)和侵蚀期(7-11月),生成期混合层盐度(Mixed Layer Salinity;MLS)决定着隔离期和侵蚀期的CLS,而MLS年代际变化则主要由同太平洋年代际涛动存在负相关性的海表面淡水通量的变化引起。  相似文献   

边带分离型超导SIS接收机本振耦合噪声研究          下载免费PDF全文

李振强  张旭国  李积斌  左营喜  徐烨  张海龙  金风娟 《天文学报》2020,61(2):18-84

超导SIS (Superconductor-Insulator-Superconductor)接收机因极低的接收机噪声温度成为毫米波和亚毫米波段射电天文观测的首选.本振系统耦合噪声也是接收机噪声的一部分,在多年的天文观测中,发现本振耦合噪声无法完全忽略,对天文观测的灵敏度有一定影响.采用两个不同种类的信号发生器作为本振系统初级信号源,测试了超导SIS接收机的噪声温度,发现信号发生器输出的基底噪声能够耦合到接收机内部,从而增加接收机噪声强度.分析研究了本振系统热噪声和信号发生器基底噪声对接收机噪声的影响.通过在信号发生器输入端加入窄带滤波器滤除其基底噪声,消除了信号发生器基底噪声引入的接收机噪声,降低了接收机的整体噪声,提高了望远镜的灵敏度.  相似文献   

Burial and exhumation of the Hoh Xil Basin,northern Tibetan Plateau: Constraints from detrital (U-Th)/He ages     

Jin-Gen Dai  Matthew Fox  David L. Shuster  Jeremy Hourigan  Xu Han  Ya-Lin Li  Cheng-Shan Wang 《Basin Research》2020,32(5):894-915

The uplift and associated exhumation of the Tibetan Plateau has been widely considered a key control of Cenozoic global cooling. The south-central parts of this plateau experienced rapid exhumation during the Cretaceous–Palaeocene periods. When and how the northern part was exhumed, however, remains controversial. The Hoh Xil Basin (HXB) is the largest late Cretaceous–Cenozoic sedimentary basin in the northern part, and it preserves the archives of the exhumation history. We present detrital apatite and zircon (U-Th)/He data from late Cretaceous–Cenozoic sedimentary rocks of the western and eastern HXB. These data, combined with regional geological constraints and interpreted with inverse and forward model of sediment deposition and burial reheating, suggest that the occurrence of ca. 4–2.7 km and ca. 4–2.3 km of vertical exhumation initiated at ca. 30–25 Ma and 40–35 Ma in the eastern and western HXB respectively. The initial differential exhumation of the eastern HXB and the western HXB might be controlled by the oblique subduction of the Qaidam block beneath the HXB. The initial exhumation timing in the northern Tibetan Plateau is younger than that in the south-central parts. This reveals an episodic exhumation of the Tibetan Plateau compared to models of synchronous Miocene exhumation of the entire plateau and the early Eocene exhumation of the northern Tibetan Plateau shortly after the India–Asia collision. One possible mechanism to account for outward growth is crustal shortening. A simple model of uplift and exhumation would predict a maximum of 0.8 km of surface uplift after upper crustal shortening during 30–27 Ma, which is insufficient to explain the high elevations currently observed. One way to increase elevation without changing exhumation rates and to decouple uplift from upper crustal shortening is through the combined effects of continental subduction, mantle lithosphere removal and magmatic inflation.  相似文献   

松辽盆地北部上二叠统林西组地球化学特征及地质意义     

张健  张海华  陈树旺  郑月娟  张德军  苏飞  黄欣 《吉林大学学报(地球科学版)》2020,50(2):518-530

为探讨松辽盆地北部林西组地球化学特征、沉积环境及构造背景，对该区黑富地1井所钻遇的上二叠统林西组暗色泥质板岩进行主量元素、微量元素和稀土元素测试分析，结果表明：样品主量元素平均质量分数SiO₂为65.05%、Al₂O₃为17.23%、CaO为2.58%、Na₂O为2.84%、K₂O为3.29%，K₂O/Na₂O值为0.20~3.48，A1₂O₃/（CaO+Na₂O）值为0.41~8.01；稀土元素w（∑REE）值介于80.68×10^-6~215.59×10^-6之间，平均值为173.41×10^-6，δEu值介于0.61~0.88之间，平均值为0.70，表现为Eu的负异常，δCe值介于0.91×10^-6~1.01×10^-6之间，为微弱的Ce负异常，LREE富集，HREE亏损；微量元素以亏损Nb、Ta、Sr，相对富集Rb、Ba、La、Ce、Pb、Nd、Sm为特征。样品元素分析和物源w（TiO₂）-w（Ni）、La/Th-w（Hf）等判别图解表明，林西组沉积物源具有多样性，主要来源于上地壳长英质物源，还有少量来自中、基性岩火成岩物源区。样品微量元素标准化蛛网图，稀土元素球粒陨石标准化配分模式图，K₂O/Na₂O-w（SiO₂）、Th-Co-Zr/10、F₂-F₁构造背景判别图及地球化学参数对比结果表明，松辽盆地北部林西组物源构造背景主要为活动大陆边缘和大陆岛弧，可能形成于靠近大陆岛弧的活动大陆边缘构造背景。林西组应形成于海陆过渡相到陆相环境，水体由半咸水逐渐转变为淡水。  相似文献   

Mineralogy,Fluid Inclusion,and Hydrogen and Oxygen Isotope Studies of the Intrusion‐Related Yangla Cu Deposit in the Sanjiang Region,SW China: Implications for Metallogenesis and Deposit Type     

Li‐Juan Du  Bo Li  Zhi‐Long Huang  Jun Chen  Jia‐Xi Zhou  Guo‐Fu Zou  Zai‐Fei Yan 《Resource Geology》2020,70(1):28-49

The Yangla deposit is an intrusion‐related Cu deposit in the Jinshajiang tectonic belt (eastern Sanjiang region, SW China). Despite extensive studies that have been conducted on this deposit, the relationship between the granitic magma and Cu mineralization is still unclear, and hence, the genesis is debated. To answer this question, we conducted an integrated study of mineralogy, fluid inclusions (FIs), and hydrogen and oxygen (H‐O) isotopes. Three mineralization stages were identified based on the ore textures, alteration zonation, and crosscutting relationships: (i) pre‐ore prograde skarn (stage I), with the garnet and pyroxene dominated by andradite and diopside, respectively; (ii) syn‐ore retrograde alteration (stage II), which is subdivided into the early syn‐ore stage (stage IIa) marked by retrograde hydrated mineral assemblages and significant Fe‐Cu‐Mo‐Pb‐Zn sulfide mineralization, and the late syn‐ore stage (stage IIb) featured by quartz‐calcite veins; and (iii) late supergene mineralization (stage III), which is characterized by secondary azurite and malachite. These results of mineralogy, FIs, and H‐O isotopes indicate that: (i) Cu mineralization has a close temporal, spatial, and genetic relationship with skarn alteration; (ii) the ore fluids were magmatic dominated with late‐stage meteoric water incursion; and (iii) Type‐S (halite‐bearing) and Type‐V (vapor‐rich) FIs coexisted in garnet and clinopyroxene of stage I, indicating that fluid boiling might have occurred during this stage. From stage I to stage IIa, the FI type transformed from Type‐S + Type‐V + Type‐L (liquid‐rich) to Type‐V + Type‐L with the conduct of mineralization and was accompanied by the disappearance of Type‐S, and homogenization temperature and salinity also tended to decrease dramatically, which may be caused by the deposition of skarn minerals. At stage IIa, boiling of the ore fluids still continued due to the change from lithostatic to hydrostatic pressure, which triggered the precipitation of abundant quartz‐Cu‐Mo‐Fe sulfides. Furthermore, fluid mixing between a high‐temperature magmatic fluid and a low‐temperature meteoric water might cause a considerable drop in temperature and the deposition of Cu‐bearing quartz/calcite veins during stage IIb. Hence, we consider the Yangla deposit to be of a skarn type, genetically related to the Mesozoic magmatism in the Sanjiang region.  相似文献   

渤海湾盆地歧口凹陷地层压力结构特征     

姜文亚  宋泽章  周立宏  蒲秀刚  王娜  代昆  万伟超  刘祥柏 《吉林大学学报(地球科学版)》2020,50(1):52-69

深化含油气沉积盆地的压力结构研究，厘清异常压力的空间展布，对划分含油气系统、评价有利输导体系与明确勘探甜点区带具有重要的理论和实践意义。为深化渤海湾盆地富油凹陷的油气二次勘探，本文以歧口凹陷为研究对象，对其压力结构进行重点刻画。在实测地层压力的校正下，综合单井、连井和二维地震地层压力结构分析，厘清了歧口凹陷的压力结构特征，识别出4类纵向压力结构：①单超压带结构；②双超压带结构；③多超压带结构；④静水压力结构。纵向上，歧口地区存在3类纵向压力系统样式——单超压系统、双超压系统、静水常压系统。双超压系统是歧口凹陷的主要压力系统样式，广泛发育于主凹和各大次凹；从凹陷中心向盆地边缘，双超压系统逐渐向单超压系统、静水常压系统过渡。单超压系统主要分布于盆地边缘的斜坡和潜山区，如歧北高斜坡、羊三木-扣村潜山等。静水常压系统则主要分布在离深凹区更远的沈青庄潜山和埕北斜坡区域。上部超压系统和下部超压系统的顶板分别位于东营组和沙三段内部，侧向上受盆地边缘和深大断裂控制。上部超压系统的形成主要受欠压实作用控制，以歧口主凹为中心呈环带分布；而下部超压系统的形成主要受生烃作用控制，以主凹和几大次凹为中心分布。未来，下部超压系统中保存的天然气将成为歧口地区超深层天然气勘探的重点对象。  相似文献   

四川盆地广安地区中二叠统栖霞组岩石特征与沉积环境     

易海永  崔宝琛  王瑶琳  邱玉超  徐胜林  李乾 《吉林大学学报(地球科学版)》2020,50(2):454-464

四川盆地中二叠统栖霞组勘探发现系列油气，资源潜力巨大。但广安地区中二叠统栖霞组的岩石学特征及沉积环境研究薄弱。在野外地质调查的基础上，结合室内岩石学、岩相学等综合分析，对广安地区栖霞组碳酸盐岩岩石特征、沉积相类型及其古地理展布特征进行了系统研究。结果表明：广安地区栖霞组主要发育亮晶颗粒灰岩、亮晶生物碎屑灰岩、微晶生物碎屑灰岩、微晶颗粒灰岩、生物碎屑微晶灰岩、含生物碎屑微晶灰岩和泥晶灰岩7种岩石类型；碳酸盐岩颗粒主要以生物碎屑为主，部分层位发育球粒；古生物化石以三叶虫、腕足和有孔虫为主，同时可见棘皮类和藻类；栖霞组沉积期主要为碳酸盐岩台地沉积环境，其中栖霞组晚期（栖二段）台缘滩和台内滩较为发育，为该区油气成藏提供了有利条件。  相似文献   

尺度政治视角下的新安江流域生态补偿政府主体博弈     

任以胜  陆林  虞虎  朱道才 《地理学报》2020,75(8):1667-1679

流域生态补偿是中国跨区域生态治理和自然区域保护的一项重要经济、社会、环境政策,涉及区域利益主体权益差异与协调、区域生态协同发展和合作模式构建等方面,是一个典型的地理学研究命题。本文将制度粘性引入到尺度政治理论中,剖析新安江流域生态补偿政府主体的博弈行为,探究不同政府主体的博弈特征和博弈机制。结果表明:中央政府、省级政府、市级政府等不同层级政府主体经历了竞争博弈、合作博弈和竞合博弈3个阶段,构建政府利益共同体能够推进流域生态补偿建设,中央政府的“适度介入”是开展跨省流域生态补偿的关键;流域生态补偿制度从“垂直”模式向“垂直—水平”模式的变迁过程中存在明显的制度粘性,政府主体利用政策革新和社会参与等制度约束稀释制度粘性,重塑流域生态补偿制度;尺度转换是推动新安江流域生态补偿的核心机制,政府主体通过重新分配权力和资本、嵌入非正式约束塑造流域生态补偿话语体系,推动新安江流域生态补偿由“强国家—弱社会”向“强国家—强社会”结构模式的转变。研究结果能够为构建跨区域流域生态补偿机制提供理论支撑,为合理评价和指导流域生态补偿实践、促进流域经济社会协调可持续发展提供科学依据。  相似文献   

Recognition of two contrasting structural-and mineralogical-gold mineral systems in the Youjiang basin,China-Vietnam:Orogenic gold in the south and Carlin-type in the north     

《地学前缘(英文版)》2020,11(5):1477-1494

The gold deposits in the Youjiang basin,totaling 25 Moz gold,have traditionally been thought to be of Carlintype,particularly those with extensional structural geometries in the northern basin dominated by platform sedimentary sequences.However,the structural geometries,mineralization styles and alteration types for the Jinya,Gaolong and Nakuang gold deposits in the south-central part of the basin are remarkably similar to those of unequivocal orogenic gold deposits.Structural studies show that gold mineralization in the three gold deposits was controlled by tight "locked-up"anticlines with NW—SE-to E-W-trending and/or concomitant thrusts and/or shear zones,which resulted from NE-SW-to N-S-trending compression or transpression following the Early Triassic closure of the Paleo-Tethyan Ocean.Alteration zones in these deposits are dominated by silicification(quartz),sericitization,sulfidation and carbonation.Zoned pyrites in these deposits comprise Au-poor cores and invisible Au-bearing rims with minor external free gold.Euhedral to subhedral auriferous arsenopyrites also contribute to the gold budget.These features indicate that the three gold deposits are sediment-hosted orogenic gold deposits that contrast markedly with the Carlin-type gold deposits in the northern part of the Youjiang basin in terms of structural geometry and timing,mineralization style and nature of associated alteration.Although additional reliable ages using robust methodologies are still required,the older isotopic ages of the gold deposits in the south-central Youjiang basin are also consistent with earlier formation during transpression that predated extension during orogenic collapse,the period of formation of the Carlin-type gold deposits in the northern Youjiang basin.  相似文献   

Main active faults and seismic activity along the Yangtze River Economic Belt: Based on remote sensing geological survey     

《China Geology》2020,3(2):314-338

The Yangtze River Economic Belt (YREB) spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and present-day crustal deformation. Active faults and seismic activity are important geological factors for the planning and development of the YREB. In this paper, the spatial distribution and activity of 165 active faults that exist along the YREB have been compiled from previous findings, using both remote-sensing data and geological survey results. The crustal stability of seven particularly noteworthy typical active fault zones and their potential effects on the crustal stability of the urban agglomerations are analyzed. The main active fault zones in the western YREB, together with the neighboring regional active faults, make up an arc fault block region comprising primarily of Sichuan-Yunnan and a “Sichuan-Yunnan arc rotational-shear active tectonic system” strong deformation region that features rotation, shear and extensional deformation. The active faults in the central-eastern YREB, with seven NE-NNE and seven NW-NWW active faults (the “7-longitudinal, 7-horizontal” pattern), macroscopically make up a “chessboard tectonic system” medium-weak deformation region in the geomechanical tectonic system. They are also the main geological constraints for the crustal stability of the YREB.  相似文献