Zircon U–Pb Age and Deformation Characteristics of the Jiama Porphyry Copper Deposit,Tibet: Implications for Relationships between Mineralization,Structure and Alteration     

Jilin Duan  Juxing Tang  Russell Mason  Wenbao Zheng  Lijuan Ying 《Resource Geology》2014,64(4):316-331

The Jiama copper deposit is one of the largest deposits recently found in Tibet and is composed of three types of mineralization including skarn, hornfels and porphyry. To investigate the relationship between mineralization, structure and alteration, we report new zircon U–Pb age and present field observations on the deformation characteritics associated with the copper mineralization in Jiama. Two main periods of deformation were identified, represented by D₁ and D₂ in Jiama. The first deformation (D₁) occurred around 50 Ma, whereas the second deformation (D₂) that was closely related to mineralization occurred later. Previous zircon U–Pb and molybnite Re–Os dating results indicate that the mineralizatoin occurred at ～15 Ma and thus the D₁ regional deformation significantly occurred before the mineralization time, although the D₁ deformation probably provided important space for the development of significant copper deposition. Our new mapping and observations on the D₂ deformation demonstrate that the mineralization was closely coeval with or slightly later than the time of D₂ deformation. The new U–Pb zircon age further indicates that the aplite formed in ～17.0 Ma and thus the D₂ deformation happened later than this time because the D₂ deformation cut across the aplite, which is proposed to be the key control for copper mineralization. Altered laminated hornfels including three types of alteration (A‐, K‐ and S‐type) were found spatially associated with the D₂ deformation. The type‐A is mainly silicification, with fine sericite or chlorite, as well as abundant disseminated sulphides on fracture surfaces; the type‐S is mainly fine‐grained silicification with patches of chlorite, epidote and common sulphides; the type‐K (potassic alteration) appears to be fine‐grained biotite. Such types of alteration indicate the presence of skarns at depth where ore shoots are located. Taken together, the multiple structural‐magmatic‐mineralization events contributed to the formation of the supergiant Jiama porphyry copper deposit in Tibet. The results have general implication for regional exploration.  相似文献   

Superthermal effect on the interactions of nonplanar electron-acoustic solitary waves in a two-electron temperature generalized Lorentzian plasma     

Jiu-Ning Han  Wen-Shan Duan  Jun-Xiu Li  Guang-Xing Dong  Su-Hong Ge 《Astrophysics and Space Science》2014,351(2):525-531

A theoretical investigation has been made on the head-on collision of cylindrical and spherical electron-acoustic solitary waves in a non-Maxwellian plasma composed of stationary ions, cold fluid electrons, and superthermal electrons obeying κ velocity distribution. By using the extended Poincaré-Lighthill-Kuo perturbation method, the effects of plasma parameters, especially the superthermal effect on the interaction of colliding solitary waves are studied. It is found that there are both positive and negative colliding phase shifts for each colliding wave in its traveling direction. Also, it is shown that the solitary waves received the largest colliding phase shifts in spherical geometry, followed by the cylindrical and planar geometries.  相似文献   

Behaviors of nonlinearities modulating the El Niño events induced by optimal precursory disturbances     

Wansuo Duan  Yanshan Yu  Hui Xu  Peng Zhao 《Climate Dynamics》2013,40(5-6):1399-1413

In the present paper, we explore the manner in which nonlinearities modulate El Niño events by investigating the optimal precursory disturbance for El Niño events in the Zebiak-Cane model. The initial anomalies of conditional nonlinear optimal perturbations (CNOPs) and linear singular vectors (LSVs) are investigated. The CNOPs evolve into stronger El Niño events than the LSVs and act as the optimal precursor for El Niño events. By examining the role of nonlinearities in El Niño events induced by CNOPs and LSVs, we determined that, when the initial anomalies of the CNOP and LSV structures are large, the nonlinearities enhance CNOP-El Niño events but suppress LSV-El Niño events. Nonlinearities in the Zebiak-Cane model arise from nonlinear temperature advection (NTA), sub-surface temperature parameterization (STP), and wind stress anomalies (WSA). Using these types of nonlinearities, we trace the approach of the nonlinearities modulating the CNOP- and LSV-El Niño events. The results demonstrate that nonlinearities that originate from NTA enhance both CNOP-El Niño events and LSV-El Niño events, while nonlinearities originating from STP and WSA suppress these events. For the CNOP-El Niño events, the enhancement effect of NTA is larger than the suppression effect of STP and WSA, resulting in the combined effect of the nonlinearities in the Zebiak-Cane model being an enhancement of the CNOP-El Niño events. However, for the LSV-El Niño events, the enhancement effect of NTA is smaller than the suppression effect of WSA and STP. Consequently, the combined effect of the nonlinearities in the Zebiak-Cane model suppresses the LSV-El Niño events.  相似文献   

村镇建设类型划分的理论与方法研究——以江苏省为例   总被引：1，自引：0，他引：1  

段学军  王磊  康珈瑜  刘圆圆 《地理科学》2022,42(2):323-332

村镇地区是多要素组合的地域单元,由于区位条件复杂多样,资源禀赋差异明显,村镇建设具有多元发展路径。基于资源环境承载力视角,构建了“压力-状态-响应”框架下的村镇建设分类指标体系,采用单向优势指标和复合指标相对优势判断相结合的划定方法,综合考虑国家和省级功能区划、协调乡镇周边区域功能并衔接省国土空间发展战略,以乡镇为分析单元,建立了省级村镇建设分类综合方案,并以江苏省为案例进行村镇建设类型划分研究。研究结果发现,江苏省仅有29.61%的乡镇为明显的单一建设类型,村镇建设的综合性发展态势明显;村镇建设类型具有明显的地域差异,苏北地区主要以居住类乡镇和生态类乡镇为主,苏中地区种植类乡镇和养殖类乡镇居多,苏南地区则集聚了商旅类和工业类乡镇。以此为基础提出不同村镇建设类型的资源环境承载力提升策略。  相似文献   

1970—2018年秦岭南北冷季降雪量时空变化及其影响因素   总被引：1，自引：0，他引：1  

李双双  段克勤  王婷  何锦屏  延军平 《地理科学》2022,42(1):163-173

基于72个气象站点逐日观测数据,对1970/1971—2018/2019年秦岭南北冷季（11月~次年5月）降水类型（降雪、降雨和雨夹雪）进行识别;重点关注降雪时空变化特征,探讨降雪与气温、湿球温度的响应关系;依据“夏季-秋季-冬季”Niño 3.4区海温异常状态,细化4种不同发展过程的厄尔尼诺-南方涛动（ENSO）事件,分析降雪异常与不同ENSO事件的对应关系。结果表明：① 相比气候平均态（1970—2000年）,1990—2018年,秦岭南坡（山地暖温带）降雪量下降了3.1 mm,基本与关中平原降雪量（17.1 mm）持平;② 空间趋势上,低海拔河谷地带降雪量以年代波动为主,山地高海拔地区为降雪下降区;③ 秦岭高山地区气温或湿球温度每升高1.0℃,降雪量分别下降23.1 mm和24.3 mm;从地带性角度分析,由北向南气温或湿球温度每升高1.0℃,秦岭南北降雪量分别下降3.0 mm和2.8 mm;④ 当厄尔尼诺/拉尼娜持续型发生时,关中平原降雪异常偏多;当拉尼娜发展型发生时,秦岭山地和大巴山区降雪异常偏少。当厄尔尼诺发展型发生时,秦岭南北降雪异常呈现“东西分异”,秦岭山地东部和关中平原为降雪异常偏少区。  相似文献   

基于多源遥感和机器学习方法的科尔沁沙地植被覆盖度反演     

张亦然  刘廷玺  童新  段利民  贾天宇  季亚新 《中国沙漠》2022,42(3):187-195

植被覆盖度是监测生态系统及其功能的关键参数,如何提高大区域植被覆盖度的反演精度,对生态脆弱区环境可持续发展至关重要。本研究基于人工神经网络、支持向量回归和随机森林等机器学习方法,利用无人机、Worldview-2与Landsat 8 OLI遥感数据,对科尔沁沙地植被覆盖度进行多尺度反演。结果表明：随机森林模型比人工神经网络、支持向量回归模型表现佳,可在单元（试验区）、区域（研究区）尺度上较高精度地反演沙地的植被覆盖度,反演值与无人机实测值均在线性水平上呈显著相关（P<0.01）;在单元、区域尺度上,构建的植被覆盖度反演模型测试集R²分别为0.84、0.80,MSE分别为0.0145、0.0370,一致性指数d分别为0.9576、0.8991。利用多源遥感数据和机器学习方法,通过局部区域的高精度反演逐步实现低空间分辨率遥感影像的大区域植被覆盖度反演,不仅可有效提高沙地植被覆盖度的反演精度（R²=0.78,大于0.63）,也为区域生态环境监测与生态系统健康评价提供支持。  相似文献   

Anomalous atmospheric events leading to Kyushu’s flash floods,July 11–14, 2012     

Weili Duan  Bin He  Kaoru Takara  Pingping Luo  Daniel Nover  Yosuke Yamashiki  Wenrui Huang 《Natural Hazards》2014,73(3):1255-1267

During July 11–14, 2012, deadly floods and landslides triggered by a series of unprecedented heavy rains hit Kyushu, Japan, causing at least 32 deaths and around 400,000 evacuations. We focus on synoptic anomalies identified after inspecting rainfall patterns and documenting the conditions associated with this tragic event using data combined from the Global Rainfall Map in Near Real Time data, the NCEP/NCAR Reanalysis dataset, and the global forecast system. Rainfall maps indicated that there were many heavy rains in Kyushu in these days and this disaster was associated with the pattern of forecasts and standardized anomalies. A weather trough with positive height anomalies appeared, the center of which moved to the north of Japan over this period, which might cause wind anomalies and whereby lots of water vapor were transported to Kyushu area with up to 90 m s^?1, and high values of precipitable water formed with up to 60 mm. These results suggest that a larger-scale pattern is conducive for heavy rainfall and the anomalies put the pattern in context as to the potential for an extreme rainfall event, which can provide insights and methods for predicting extreme events’ or something similar.  相似文献   

Statistics of underwater ambient noise at high sea states arisen from typhoon out zones in the Philippine Sea and South China Sea     

Qiulong Yang  Kunde Yang  Shunli Duan  Yuanliang Ma 《海洋学报(英文版)》2022,41(7):153-165

Oceanic noise is the background interference in sonar performance prediction and evaluation at high sea states. Statistics of underwater ambient noise during Typhoons Soulik and Nida were analyzed on the basis of experimental measurements conducted in a deep area of the Philippine Sea and the South China Sea. Generated linear regression, frequency correlation matrix (FCM), Burr distribution and Gumbel distribution were described for the analysis of correlation with environmental parameters including wind speed (WS), significant wave height (SWH), and the inter-frequency relationship and probability density function of noise levels (NLs). When the typhoons were quite close to the receivers, the increment of NLs exceeded 10 dB. Whilst ambient noise was completely dominated by wind agitation, NLs were proportional to the cubic and quintic functions of WS and SWH, respectively. The fitted results between NLs and oceanic parameters were different for “before typhoon” and “after typhoon”. The fitted slopes of linear regression showed a linear relationship with the logarithm of frequency. The average observed typhoon-generated NLs were 5 dB lower than the Wenz curve at the same wind force due to the insufficiently developed sea state or the delay between NLs and WS. The cross-correlation coefficient of FCM, which can be utilized in the identification of noise sources in different bands, exceeded 0.8 at frequencies higher than 250 Hz. Furthermore, standard deviation increased with frequency. The kurtosis was equal to 3 at >400 Hz approximately. The characteristics of NLs showed good agreement with the results of FCM.  相似文献   

冕洞的演化规律     

段长春  罗葆荣  曹莹  侯叔明 《天文研究与技术》1997,(2)

本文利用自有冕洞系统观测以来（１９７０－１９９５）的冕洞资料，分析了冕洞的时空分布演化规律，冕洞磁场的演化特征，以及它们与太阳黑子周期的演化关系。得到了一些有意义的新结论。特别是赤道冕洞和极区冕洞与太阳活动周的演化关系具有截然相反的演化规律和不同特征。前者与太阳活动周的演化规律基本一致；后者截然相反  相似文献   

Kinetic Alfvén wave driven by the density inhomogeneity in the presence of loss-cone distribution function—particle aspect analysis     

S.P. Duan  Z.Y. Li 《Planetary and Space Science》2005,53(11):1167-1173

Kinetic Alfven waves (KAWs) driven by the diamagnetic drift instability that is excited by the density inhomogeneity in low-β plasmas, such as plasmas in the auroral region, are investigated by adopting the particle aspect analysis and loss-cone distribution function. The results obtained in this paper indicate that the propagation and evolution of kinetic Alfven waves decrease and the kinetic Alfven wave excitation becomes not easier with increasing loss-cone index J. But the spatial scales of the perpendicular perturbation driving kinetic Alfven waves have a decreasing tendency with the larger values of J, which perhaps is in relation with the decreasing width of loss-cone. A single hump appears in the plots of the growth rate of the instability when J=2. But the hump cannot emerge when J=0 or J=1. The density inhomogeneity of ions plays an important role in driving KAWs and it cannot be ignored. KAWs can be easier driven and KAWs can propagate and evolve faster with the increasing level of density inhomogeneity. However, the range of the perpendicular wave number of the wave instability decreases, namely, the longer the scale of perpendicular disturbance the easier the excitation of KAW. As the density inhomogeneity increases, the tendency of numerical solutions of the dispersion relation is similar to that obtained by the kinetic theory and Maxwellian distribution function (Duan and Li, 2004). But the profiles of the plots of numerical solutions are different. This means that the velocity distribution function of particles is important for KAW driven in magnetoplasmas, especially in the active regions of the magnetosphere, such as auroral region, and plasma sheet boundary.  相似文献