贺兰山—银川地堑及邻区重力异常特征及构造意义

贺兰山—银川地堑及邻区地质结构复杂,对该区域深浅结构特征的研究具有重要意义.本文采用重力归一化总梯度成像和二维小波多尺度分解方法对研究区内重力异常进行了垂向和横向构造分析.重力归一化总梯度成像结果显示高低转换带的倾角、倾向与地质上的贺兰山东麓断裂、银川断裂和黄河断裂分布吻合较好,贺兰山西麓断裂与贺兰山东麓断裂汇交深度约18 km,银川断裂与黄河断裂汇交深度约25 km;二维小波多尺度分解成像结果表明正谊关断裂、贺兰山西麓断裂、芦花台断裂和银川断裂为上地壳断裂,贺兰山东麓断裂、青铜峡—固原断裂以及黄河断裂为下地壳断裂,且这三大断裂可能分别是阿拉善地块东南边界和鄂尔多斯地块西南边界;1739年平罗M 8.0古地震震中与银川断裂在重力剖面深度约15 km汇交,其垂向高低梯度为强变形带,同时古地震震中位于重力正负异常转换部位的低值区,据此可推断此次古地震的发震构造是银川断裂.这些结论可提高对贺兰山—银川地堑及邻区地质结构的认识,为该区地壳动力学过程及强震的孕震机理研究提供一定的科学依据.     

珠江口洪季最大浑浊带的大小潮变化与机制分析*

基于ROMS三维模型, 模拟了珠江口洪季最大浑浊带的轴、侧向分布和大、小潮变化。模拟结果表明, 珠江口伶仃洋最大浑浊带的轴向位置在22.3°—22.45°N之间, 并随着潮流变化而周期性上下游迁移。控制最大浑浊带形成的主要因素是余流作用下的底层泥沙辐聚, 决定最大浑浊带位置的主要因素是水平对流输沙, 泥沙来源主要是上游浅滩沉积物的再悬浮。小潮期间堆积在浅滩的细颗粒沉积物在大潮期间被悬浮, 搬运到下游的滞流点位置, 在中滩南部和西滩外缘落淤。“潮泵”作用在大潮期间将泥沙向下游输运, 在小潮期间向上游输运; 垂向剪切作用则有利于悬浮泥沙的陆向输运; 二者共同作用产生泥沙辐聚, 形成最大浑浊带。大、小潮期间余流结构差异不大, 主要由密度差和潮汐混合不对称共同导致, 其中前者贡献更大。     

Tropical cyclones and multiscale climate variability: The active western North Pacific Typhoon season of 2018

The 2018 typhoon season in the western North Pacific(WNP) was highly active, with 26 named tropical cyclones(TCs) from June to November, which exceeded the climatological mean(22) and was the second busiest season over the past twenty years. More TCs formed in the eastern region of the WNP and the northern region of the South China Sea(SCS). More TCs took the northeast quadrant in the WNP, recurving from northwestward to northward and causing heavy damages in China's Mainland(69.73 billion yuan) in 2018. Multiscale climate variability is conducive to an active season via an enhanced monsoon trough and a weakened subtropical high in the WNP. The large-scale backgrounds in 2018 showed a favorable environment for TCs established by a developing central Pacific(CP) El Ni?o and positive Pacific meridional mode(PMM)episode on interannual timescales. The tropical central Pacific(TCP) SST forcing exhibits primary control on TCs in the WNP and large-scale circulations, which are insensitive to the PMM. During CP El Ni?o years, anomalous convection associated with the TCP warming leads to significantly increased anomalous cyclonic circulation in the WNP because of a Gill-type Rossby wave response. As a result, the weakened subtropical high and enhanced monsoon trough shift eastward and northward, which favor TC genesis and development. Although such increased TC activity in 2018 might be slightly suppressed by interdecadal climate variability, it was mostly attributed to the favorable interannual background. In addition, high-frequency climate signals,such as intraseasonal oscillations(ISOs) and synoptic-scale disturbances(SSDs), interacted with the enhanced monsoon trough and strongly modulated regional TC genesis and development in 2018.     

Movements of the Western Pacific Warm Pool Centroid and Their Relationship to Sea Surface Temperature Changes in Ni(n)o Regions

By using monthly historical sea surface temperature (SST) data for the years from 1950 to 2000, the Western Pacific Warm Pool (WPWP) climatology and anomalies are studied in this paper. The analysis of WPWP centroid (WPWPC) movement anomalies and the Nino-3 region SST anomalies( SSTA) seems to reveal a close, linear relation between the zonal WPWPC and Nino-3 region SSTA, which suggests that a 9' anomaly of the zonal displacement from the climatological position of the WPWPC corresponds to about a 1 ℃ anomaly in the Nino-3 region area-mean SST. This study connects the WPWPC zonal displacement with the Nino-3 SSTA, and it may be helpful in better understanding the fact that the WPWP eastward extension is conducive to the Nino-3 region SST increase during an El Nino-Southern Oscillation (ENSO) event.     

珠江三角洲土地利用变化与工业化和城市化的耦合关系

在分析珠江三角洲1990～2000年土地利用变化趋势和特征的基础上，根据土地利用的综合变动系数将珠江三角洲划分为4种土地变化类型，即剧变型、缓变型、相对稳定型和稳定型，并总结了不同变化类型的特征。进一步研究了工业化、城市化发展阶段与土地利用变化类型的关系，结果显示，处于不同工业化、城市化阶段的县市，其土地利用变化也明显不同，且与工业化、城市化进程和状态具有一定的内在关系；最后对产业非农化、城市化与土地利用变化的耦合系数进行了研究，发现各市县的产业非农化、城市化和土地利用变化的耦合系数，与土地利用的综合变动系数具有很高的一致性，按照产业非农化、城市化和土地利用变化耦合系数，在一定程度上可以判断土地变化的类型。     

Ree geochemistry characteristics of stratigraphic samples in the abalieke region,Western Kunlun北大核心

The Abalieke region locats in the central section of the western Kunlun polymetallic (Pb, Zn, Cu, etc) ore belt, an area with major potential for further base metal deposit discoveries. This paper reports REE data for 82 samples from 8 stratigraphic sections for Huoshilafu formation in the Abalieke region. To attempt to solve the origin of ore-forming materials using REE geochemistry. Although total REE contents are quite variable ( Σ REE = 7. 52 × 10-6-220. 70 × 10-6, ΣLREE = 5. 82 × 10-6-198. 46 × 10-6, ΣHREE = 1. 49 × 10-6- 32. 74 × 10-6 and Y = 4. 77 × 10-6-91. 30 × 10-6) , chondrite-normalized REE patterns of the majority of samples are uniformly LREE-enriched (averaging ΣLREE/ΣHREE = 6. 57), with remarkably fractionation of LREE and HREE [averaging (La/Yb)N = 8. 20], slightly negative Eu anomalies (averaging δEu = 0. 77) and insignificant Ce anomalies (averaging δCe = 0. 88). The results demonstrate that REE characteristics of stratigraphic samples from Abalieke region are similar to those of rock and ore samples from other representative deposits (Tiekelike, Tamu, Kalangu, Tuokuziate) in the western Kunlun polymetallic ore belt, which indicate a close genetic relationship between the ore-forming materials and the host strata for the majority of deposits in this belt.     

西天山小于赞金矿成矿流体、成矿年代学特征及其地质意义

小于赞金矿床是产于新疆西天山也列莫顿盆地的浅成低温热液型金矿床,赋存于晚古生代大哈拉军山组火山岩中。矿石类型主要为蚀变岩型和石英脉型,主要发育硅化、黄铁绢英岩化、伊利石化、青磐岩化蚀变。流体成矿过程可分为3个阶段,分别为石英黄铁矿、石英玉髓黄铁矿和石英方解石黄铁矿阶段。小于赞金矿床流体包裹体类型单一,主要为水溶液包裹体,可分为纯液相水溶液包裹体(PL类)、富液相水溶液包裹体(L类)和富气相水溶液包裹体(V类)。石英黄铁矿阶段包裹体均一温度集中于130~190 ℃,盐度w(NaCleqv.)为0.2%~8.0%;石英玉髓黄铁矿阶段均一温度介于115~161 ℃,盐度w(NaCleqv.)为0.7%~3.4%;石英方解石黄铁矿阶段均一温度介于110~138 ℃,盐度w(NaCleqv.)为0.2%~3.4%。鉴于赋矿角砾凝灰岩的锆石U-Pb年龄为(353.8±1.8) Ma,且被下石炭统阿恰勒河组不整合覆盖,故可将小于赞金矿床的成矿时代限定在(353.8±1.8) Ma至早石炭世维宪期。锆石εHf(t)变化范围为+4.1~+8.4,平均值+6.1,两阶段Hf模式年龄tDM2变化范围为822~1 095 Ma,指示该区岩浆演化过程中有少量地幔物质的加入。综合考量矿床地质特征、流体包裹体特征和成矿时代,认为小于赞矿床为早石炭世低硫型浅成低温热液型金矿。     

长江三角洲地区TZK3孔碎屑锆石U-Pb年龄及其物源意义

以TZK3孔的磁性地层学为基础,结合沉积物的岩性、结构构造及锆石年龄谱系特征,探讨沉积物的物质来源及长江贯通的时限。古地磁结果表明:96.7 m、263.3 m、603.75 m分别对应B/M界线、M/G界线、晚上新世/早上新世的界线（3.58 Ma）。锆石年龄谱系数据显示,TZK3孔的U-Pb锆石年龄主要分为5组:100~300 Ma,400~500 Ma,700~850 Ma,1800~2000 Ma,2400~2600 Ma。其中3.7 Ma的锆石年龄谱相对简单,以白垩纪（100~150 Ma）为主,物质主要来自于长江中下游的火山盆地,为近源沉积。TZK3孔3.04 Ma以来,锆石年龄谱变得复杂且主峰相对较多,表明物源区更广且加入了远源的成分。3.04 Ma的锆石年龄谱中开始出现峨眉山玄武岩年龄段（251~260 Ma）的锆石,表明在此时期长江上游的物质就已到达了长江三角洲地区,即长江贯通的时限为3.04~3.7 Ma。      

Geochemistry,origin, and accumulation of petroleum in the Eocene Wenchang Formation reservoirs in Pearl River Mouth Basin,South China Sea: A case study of HZ25-7 oil field

The Pearl River Mouth Basin in the South China Sea has accumulated >2 km of Eocene sediments in its deep basin, and has become the exploration focus due to the recent discoveries of the HZ25-7 oil field in the Eocene Wenchang (E₂w) Formation. In this study, the geochemical characteristics of potential source rocks and petroleum in the HZ25-7 oil field are investigated and the possible origins and accumulation models developed. The analytical results reveal two sets of potential source rocks, E₂w and Enping (E₂e) formations developed in the study area. The semi-deep-to-deep lacustrine E₂w source rocks are characterized by relatively low C₂₉ steranes, low C₁₉/C₂₃ tricyclic terpane (<0.6), low C₂₄ tetracyclic terpane/C₃₀ hopane (<0.1), low trans-trans-trans-bicadinane (T)/C₃₀ hopane (most <2.0), and high C₃₀ 4-methyl sterane/ΣC₂₉ sterane (>0.2) ratios. In contrast, the shallow lacustrine and deltaic swamp-plain E₂e source rocks are characterized by relatively high C₂₉ steranes, high C₁₉/C₂₃ tricyclic terpane (>0.6), high C₂₄ tetracyclic terpane/C₃₀ hopane (>0.1), variable yet overall high T/C₃₀ hopane, and low C₃₀ 4-methyl sterane/ΣC₂₉ sterane (<0.2) ratios. The relatively low C₁₉/C₂₃ tricyclic terpane ratios (mean value: 0.39), low C₂₄ tetracyclic terpane/C₃₀ hopane ratios (mean value: 0.07), high C₃₀ 4-methyl sterane/ΣC₂₉ sterane ratios (mean value: 1.14), and relatively high C₂₇ regular sterane content of petroleum in the HZ25-7 oil field indicate that the petroleum most likely originated from the E₂w Formation mudstone in the Huizhou Depression. One stage of continuous charging is identified in the HZ25-7 oil field; oil injection is from 16 Ma to present and peak filling occurs after 12 Ma. Thin sandstone beds with relatively good connectivity and physical properties (porosity and permeability) in the E₂w Formation are favorable conduits for the lateral migration of petroleum. This petroleum accumulation pattern implies that the E₂w Formation on the western and southern margins of the Huizhou Depression are favorable for petroleum accumulation because they are located in a migration pathway. Thus exploration should focus in these areas in the future.     

High-resolution sequence stratigraphy,sedimentology and reservoir quality evaluation of the Yaojia Formation in the Longxi area of the Western Slope,Songliao Basin,China

Delta-front sand bodies with large remaining hydrocarbon reserves are widespread in the Upper Cretaceous Yaojia Formation in the Longxi area of the Western Slope, Songliao Basin, China. High-resolution sequence stratigraphy and sedimentology are performed based on core observations, well logs, and seismic profile interpretations. An evaluation of the reservoir quality of the Yaojia Formation is critical for further petroleum exploration and development. The Yaojia Formation is interpreted as a third-order sequence, comprising a transgressive systems tract (TST) and a regressive systems tract (RST), which spans 4.5 Myr during the Late Cretaceous. Within this third-order sequence, nine fourth-order sequences (FS9–FS1) are recognized. The average duration of a fourth-order sequence is approximately 0.5 Myr. The TST (FS9–FS5) mostly comprises subaqueous distributary channel fills, mouth bars, and distal bars, which pass upward into shallow-lake facies of the TST top (FS5). The RST (FS4–FS1) mainly contains subaqueous distributary-channel and interdistributary-bay deposits. Based on thin-sections, X-ray diffraction (XRD), scanning electron microscope (SEM) and high-pressure mercury-intrusion (HPMI) analyses, a petrographic study is conducted to explore the impact of the sedimentary cyclicity and facies changes on reservoir quality. The Yaojia sandstones are mainly composed of lithic arkoses and feldspathic litharenites. The sandstone cements mostly include calcite, illite, chlorite, and secondary quartz, occurring as grain coating or filling pores. The Yaojia sandstones have average core plug porosity of 18.55% and permeability of 100.77 × 10⁻³ μm², which results from abundant intergranular pores and dissolved pores with good connectivity. Due to the relatively coarser sediments and abundant dissolved pores in the feldspars, the FS4–FS1 sandstones have better reservoir quality than the FS9–FS5 sandstones, developing relatively higher porosity and permeability, especially the FS1 and FS2 sandstones. The source–reservoir–cap-rock assemblages were formed with the adjoining semi-deep lake mudstones that were developed in the Nenjiang and Qingshankou Formations. This study reveals the deposition and distribution of the delta-front sand bodies of the Yaojia Formation within a sequence stratigraphic framework as well as the factors controlling the Yaojia sandstones reservoir quality. The research is of great significance for the further exploration of the Yaojia Formation in the Longxi area, as well as in other similar lacustrine contexts.