黑龙江多宝山地区早古生代沟-弧-盆体系重建SCIEI北大核心CSCD

沟-弧-盆体系恢复对于研究增生造山过程和解析成矿作用具有重要指示意义,多宝山岛弧带是我国重要的铜钼多金属成矿区带,其沟-弧-盆体系恢复对成矿地质背景研究及拓展区域找矿具有重要意义。通过对多宝山地区早古生代地层、岩石和构造的野外调研和系列编图,结合最新的年代学资料,重新厘定了含矿地层单位——多宝山组、铜山组的形成时代和层位:确定多宝山组形成时代为寒武纪芙蓉世-早奥陶世,铜山组形成时代为早-中奥陶世;将铜山组置于多宝山组之上,暗示地表以下保存有规模较大的主要成矿地质体——多宝山组,由此扩大了深部找矿空间。在此基础上,重建了多宝山岛弧带早古生代地层序列。在多宝山岛弧带西北侧多宝山-三卡一带划分出早古生代俯冲增生杂岩带,根据俯冲增生杂岩带与岩浆弧、伴生沉积盆地的沉积建造及时空关系,划分出弧前盆地、弧间盆地、弧后盆地等构造单元,建立了多宝山岛弧带古生代沟-弧-盆体系格架,认为多宝山岛弧带西北侧多宝山-三卡一带存在早古生代洋盆,并于奥陶纪发生南东向俯冲。指出岩浆弧靠近俯冲增生杂岩带一侧是成矿有利部位,为多宝山岛弧带铜多金属矿的成矿背景和成矿地质条件研究提供了理论依据。     

准噶尔盆地东北缘石炭系火山岩形成机制:对准噶尔洋盆闭合时限的新启示

准噶尔古大洋作为古亚洲洋北部的重要分支及阶段性演化产物,其洋盆的俯冲、闭合时限以及盆地基底属性一直存在分歧。本文选取准噶尔盆地东北缘(乌伦古地区)石炭系火山岩来说明其岩浆来源及成因机制,通过主微量元素、Sr-Nd同位素分析结果,进一步阐明准噶尔洋盆在晚古生代的闭合时限。本次研究包括玄武岩、玄武质安山岩和安山岩三类火山岩,岩体显示低TiO₂(0.60%~0.84%)、较高的全碱K₂O+Na₂O含量(1.18%~8.59%),玄武岩为岛弧拉斑系列,安山岩类的钙碱元素含量高,具有火山弧火山岩特征。中-低⁸⁷Sr/⁸⁶Sr_(i)(0.703 250~0.704 559)、相对亏损的Nd同位素(+4.8~+6.8)以及t_DM2(483~625 Ma)值表明玄武岩、玄武质安山岩和安山岩同为亏损地幔熔融岩浆分异结晶的产物,安山岩为地幔熔融岩浆后期分离结晶形成;微量元素与同位素地球化学示踪暗示玄武岩、玄武质安山岩和安山岩含有洋壳俯冲过程的脱水流体交代上覆地幔楔的消减组分,安山岩在深部岩浆房经历了壳-幔混合作用,受地壳成分的混染程度更大。大离子亲石元素(LILE)Ba、Sr和轻稀土元素、不相容元素(Th、U、K)相对富集,高场强元素(HFSE)Nb、Ta相对亏损,以及Pb、Zr、Hf的富集,说明该区属于与俯冲消减带相关的构造背景;结合本套火山岩高Ba/La(30.14~208.86)值、低TiO₂(0.60%~0.84%)值,以及Ce/Nb比(8.71~12.05)、Th/Nb比(0.93~1.74)等,表明准噶尔洋盆于石炭纪沿着大陆板块下部持续俯冲,洋壳板片的俯冲脱水流体交代地幔楔后增生岛弧。该套中-基性火山岩建造佐证了准噶尔洋盆闭合时限为晚石炭世(ca. 305.5±4.4 Ma),结合区域地质资料分析,提出与俯冲带有关的岩浆通过岛弧拼贴增生到大陆地壳上,进一步为准噶尔盆地基底的岛弧拼贴成因提供了新依据。     

Genesis of island dolostones

Cenozoic ‘island dolostones’ are found on islands throughout the oceans of the world. Due to their geological youth and lack of deep burial, these dolostones provide an opportunity to resolve some of the mysteries surrounding the dolomite problem. In island dolostone bodies, which are of variable size and variable dolomitization, the petrographic and geochemical properties of the dolostones are characterized by geographic and stratigraphic variations. In the larger island‐wide dolostone bodies, like those found on Grand Cayman, there are progressive increases in mole %Ca (%Ca_mean: 53·9 to 57·6%), depletion of the heavier ¹⁸O and ¹³C isotopes (δ¹⁸O_mean: 3·6 to 2·1‰ _VPDB; δ¹³C_mean: 3·1 to 1·4‰ _VPDB), and changes from fabric‐retentive to fabric‐destructive fabrics and a decrease in the amount of dolomite cement from the coastal areas towards the centres of the islands, similar to the Little Bahama Bank. These changes define geographically concentric zones that parallel the coastlines and reflect geochemical modification of the dolomitizing fluid through water–rock interactions, mixing with meteoric water and the changes in the rate and flux of seawater as it flowed from coasts to island interiors. The pattern of dolomitization, however, is not consistent from island to island because geographic and stratigraphic variations, specific to each island, influenced groundwater flow pattern (for example, geometry and size of the islands; the porosity and permeability of the precursor limestone), the duration of the dolomitization reaction, and other factors. The geographic extent of dolomitization and variation in dolomite stoichiometry of island dolostones may be comparable to the reaction stages established in high‐temperature laboratory experiments.     

西藏雄村矿区Ⅱ号矿体硫、铅同位素地球化学特征

雄村矿区位于西藏冈底斯斑岩铜矿带西段,目前在该矿区发现了Ⅰ、Ⅱ、Ⅲ号斑岩型铜金矿体。文章通过Ⅱ号矿体硫、铅同位素研究,获得Ⅱ号矿体金属硫化物的δ~(34)S值为-1.6‰~-0.6‰,平均值-1.30‰,总硫同位素值(δ~(34)S_(ΣS))为0.99‰,与含矿斑岩的硫同位素组成(-2.1‰~+1‰,平均0.06‰)一致,均落入幔源硫范围,表明硫主要来自岩浆。含矿斑岩和金属硫化物的铅同位素组成~(206)Pb/~(204)Pb、~(207)Pb/~(204)Pb、~(208)Pb/~(204)Pb分别为18.460~18.560、15.586~15.622、38.603~38.727和17.972~18.425、15.528~15.593、38.024~38.489,两者的铅同位素组成基本一致,变化范围小,表明两者具有相同的来源。所有样品的铅同位素μ值为9.34~9.49,显示幔源特征,综合源区判别图解认为铅主要来源于幔源,有少量俯冲沉积物加入,矿床形成于与洋壳俯冲消减作用有关的岛弧构造环境。     

北山造山带花牛山岛弧东段钨矿床成矿时代和成矿动力学过程

北山造山带位于中亚造山带最南缘,为多期岛弧、蛇绿混杂岩拼贴而成的增生型造山带;晚古生代,北山造山带的构造活动引发强烈的花岗质岩浆活动,伴随有广泛的钨(钼)成矿作用;本文对北山南带花牛山岛弧三个典型含钨花岗岩体:盘陀山、鹰嘴红山及玉山岩体进行详细的锆石U-Pb年代学、全岩地球化学研究。SIMS锆石U-Pb定年结果表明该区成矿花岗岩分为两个侵入期次:(1)晚志留世月牙山-洗肠井蛇绿混杂岩南段出露花岗岩,其中,盘陀山二长花岗岩422.0±1.5Ma;盘陀山钾长花岗岩417.0±1.7Ma;鹰咀红山钾长花岗岩424.0±1.3Ma;(2)晚二叠世柳园蛇绿混杂带北侧玉山花岗岩体,定年结果为280.8±3.0Ma。岩石地球化学研究表明盘陀山-鹰嘴红山花岗岩带为过铝质S型花岗岩,玉山岩体为A型花岗岩。岩体稀土含量较高,具右倾型稀土配分模式,LREE分异强烈,HREE分异不明显,样品Eu亏损强烈。原始地幔标准化蛛网图中总体显示较为一致的分布模式,大离子亲石元素Ba、Sr呈现明显负异常,富集Th、U、Pb、Zr、Hf等元素而亏损高场强元素Ta、Nb、Ti、P。结合晚古生代北山构造演化过程,推断国庆-鹰嘴红山钨矿为公婆泉岛弧与花牛山岛弧碰撞阶段形成,而玉山钨矿床为晚华力西期弧后伸展构造背景的产物。     

高分辨率遥感影像海岛礁地理信息自动变化检测方法

基于高分辨率遥感影像的海岛礁地理信息变化检测可用于普查海岛礁地理信息变化,从而为海岛礁开发利用、海洋资源保护、海洋经济发展及国防建设等提供参考。本文提出一种基于马尔科夫随机场的海岛礁地理信息自动变化检测方法,通过典型相关分析和马尔科夫随机场模型相结合的方法,提取变化区域。并以西沙赵述岛为实验区域进行方法验证。实验证明这一方法可以有效地提取海岛礁地理信息发生变化的区域。     

海岛测绘中跨海高程传递实施方法浅析

结合某海岛测绘专项的实施,论述多种方法相结合、相互验证的综合跨海高程传递实施方案,综合利用卫星定位测量、三角高程测量、大地天文测量、验潮观测和几何水准测量等多种大地测量手段,对具体的技术要求进行了论述和分析。     

URBANIZATION EFFECTS ON OBSERVED CHANGES IN SUMMER EXTREME HEAT EVENTS OVER ZHEJIANG PROVINCE, EAST CHINA

Although the urban heat island (UHI) is a well-documented phenomenon, relatively little information in the literature is available about its impact on summer extreme heat event (EHE). As UHI is characterized by increased temperature, it can potentially increase the magnitude and duration of EHEs within cities. Based on daily maximum temperature records from 62 observation stations in Zhejiang province from the period 1971-2011 and satellite-measured nighttime light imagery from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) during 1992-2010, we analyzed the long-term change of summer EHEs and its association with the rapid urbanization process. The results could be concluded as follows: (1) Zhejiang has experienced rapid urbanization and dramatic growth in urban areas in the past two decades, especially after 2000. (2) The summer mean maximum temperature and the 95th percentile of summer daily maximum temperature in most of its stations have increased, with the most significant increase occurring in the highly urbanized areas including the city belt around Hangzhou Bay, Taizhou–Wenzhou and Jinghua–Yiwu city belts. (3) The hot days and hot-day degrees, defined by both daily 95th percentile and the threshold of 35℃, show that the UHI effect causes additional hot days and heat stress in urban stations compared to rural stations. The results in this study suggest that the UHI effect should be determined and incorporated in preparing high temperature forecasts in cities.     

海岛生态脆弱性的内涵、特征及成因探析

海岛生态系统拥有明显且独特的脆弱性,对海岛的生态环境和社会经济构成威胁。准确把握和有效控制海岛生态脆弱性是维护海岛生态系统、合理开发利用海岛的根本前提,一套科学、统一且针对性强的概念体系是海岛生态脆弱性研究的基础。参考相关研究,以海岛生态系统的特殊性为基点,以我国海岛为侧重点,通过梳理和分析大量海岛典型案例,提出并探析海岛生态脆弱性的内涵、特征和成因。海岛生态脆弱性是在独特的自身条件和复杂的系统干扰下海岛生态系统表现出的易受损性和难恢复性,具备长期性、分异性和可调控性的特征;特殊的地理位置、有限的规模大小和明显的空间隔离使得海岛生态系统具有明显的海陆二相性、资源短缺性和独立完整性,与不同类型、不同程度的自然扰动和人为干扰相互作用,形成并加剧海岛生态脆弱性。概念体系的建立能够为海岛生态脆弱性的深入分析与合理调控提供切实依据。     

近三十年来曹妃甸岸线岛体时空演变特征分析

在对1979年、1987年、1991年、1997年、2002年-2005年、2008年、2012年十个时期曹妃甸遥感影像图解译的基础上,从自然地理学角度对岸线和岛体历史演变趋势进行系统分析,得到曹妃甸岸线和岛体动态变化。研究结果显示,曹妃甸岛体面积在近半个世纪发生了较大的变化,由0.34 km2增加为227.34 km2;岸线整体表现为向海推进,1979年曹妃甸陆域岸线25.21%为自然岸线,之后自然岸线比例逐渐减少,自2002年起人工岸线占据了曹妃甸陆域岸线的全部,2012年岛体整体人工岸线长度较1989年自然岸线增长10倍之多;岛体在自然演变时期呈现中部侵蚀、两端淤积、端点延长、西向漂移且中心点逐步向大陆靠拢的变化特征,自2005年起自然状态岛体已不复存在。