Size distributions and source function of sea spray aerosol over the South China Sea

The number concentrations in the radius range of 0.06 – 5 μm of aerosol particles and meteorological parameters were measured on board during a cruise in the South China Sea from August 25 to October 12, 2012. Effective fluxes in the reference height of 10 m were estimated by steady state dry deposition method based on the observed data, and the influences of different air masses on flux were discussed in this paper. The number size distribution was characterized by a bimodal mode, with the average total number concentration of(1.50 ± 0.76)×10~3 cm~(-3). The two mode radii were 0.099 μm and 0.886 μm, both of which were within the scope of accumulation mode. A typical daily average size distribution was compared with that measured in the Bay of Bengal. In the whole radius range, the number concentrations were in agreement with each other; the modes were more distinct in this study than that abtained in the Bay of Bengal. The size distribution of the fluxes was fitted with the sum of log-normal and power-law distribution. The impact of different air masses was mainly on flux magnitude, rather than the shape of spectral distribution. A semiempirical source function that is applicable in the radius range of 0.06 μmr_(80)0.3 μm with the wind speed varying from 1.00 m s~(-1) to 10.00 m s~(-1) was derived.     

基于无人船的大洋中尺度涡观测系统展望

中尺度涡在大洋中普遍存在,研究发现其能量比大尺度海洋环流的能量大一个量级,在海洋物质能量输运和全球气候变化中起着重要的作用。受观测条件限制,目前对中尺度涡的观测主要通过卫星高度计实现,只能从海面高度来推算中尺度涡大小、分布、强度及其伴随的水体和能量输送,而卫星高度计对中尺度涡垂直结构特征认识不足,也导致了对中尺度涡所引起的上层海洋能量、热量输送估计误差偏大。目前对中尺度涡三维结构观测认识不足,展望未来将会出现基于无人船平台的大洋中尺度涡三维结构自动观测系统,该平台将集成自动水下剖面观测功能等先进技术,以便观测中尺度涡的垂直结构特征及其时空变化特征,进而可对中尺度涡带来的物质和能量输送进行系统认识。     

油铀兼探的找矿思路在松辽盆地的应用——以中央拗陷区南部为例

以"油铀兼探"的找矿思路,带动松辽盆地中南部开展砂岩型铀矿调查选区及钻探验证工作.将异常强度250 API和450 API确定为划分潜在铀矿孔、潜在铀矿化孔和正常孔的关键技术指标,对中央拗陷区南部1572个钻孔进行异常筛查工作.排查发现潜在铀矿孔362个,潜在铀矿化孔223个.对191号钻孔和36号钻孔进行钻探验证,发现1个工业孔、1个异常孔.认为区内寻找砂岩型铀矿的有利地段为油田区反转构造形成的隆起区边部四方台组河流相砂体,并总结了中央拗陷区南部6种主要控矿因素.     

The dominant driving force for supercontinent breakup: Plume push or subduction retreat?

Understanding the dominant force responsible for supercontinent breakup is crucial for establishing Earth's geodynamic evolution that includes supercontinent cycles and plate tectonics. Conventionally,two forces have been considered: the push by mantle plumes from the sub-continental mantle which is called the active force for breakup, and the dragging force from oceanic subduction retreat which is called the passive force for breakup. However, the relative importance of these two forces is unclear. Here we model the supercontinent breakup coupled with global mantle convection in order to address this question. Our global model features a spherical harmonic degree-2 structure, which includes a major subduction girdle and two large upwelling(superplume) systems. Based on this global mantle structure,we examine the distribution of extensional stress applied to the supercontinent by both subsupercontinent mantle upwellings and subduction retreat at the supercontinent peripheral. Our results show that:(1) at the center half of the supercontinent, plume push stress is ～3 times larger than the stress induced by subduction retreat;(2) an average hot anomaly of no higher than 50 K beneath the supercontinent can produce a push force strong enough to cause the initialization of supercontinent breakup;(3) the extensional stress induced by subduction retreat concentrates on a ～600 km wide zone on the boundary of the supercontinent, but has far less impact to the interior of the supercontinent. We therefore conclude that although circum-supercontinent subduction retreat assists supercontinent breakup, sub-supercontinent mantle upwelling is the essential force.     

基于短波红外技术的蚀变矿物特征及勘查模型——以斯弄多银铅锌矿床为例

印度-亚洲大陆的碰撞成就了青藏高原的冈底斯成矿带,位于该成矿带的斯弄多银铅锌矿床赋存于林子宗群火山岩中,经过勘查确认该矿床属于低硫化浅成低温热液型矿床。通过对5个钻孔进行短波红外测量,发现钻孔中的蚀变矿物主要有绢(白)云母、钠云母(富Na云母)、伊利石和蒙脱石,并在垂向形成绢(白)云母→绢(白)云母+钠云母+蒙脱石+伊利石→绢(白)云母+伊利石→绢(白)云母的组合特征。通过总结归纳蚀变矿物分布、分带特征并与地质编录相结合,构建了基于短波红外技术的斯弄多找矿勘查模型。笔者在数据分析与模型构建中发现:(1)伊利石-蒙脱石混合矿物组成是寻找深部及外围矿体的重要线索;(2)绢(白)云母属于成矿前期的蚀变,与矿体之间的关系不明显;(3)矿床深部表现为两种不同的化学反应:SW方向深部反映了绢云母被交代形成伊利石的过程;NE方向深部表现为绢(白)云母二八面体结构的变化;(4)未被剥蚀的青磐岩化带是寻找浅成低温热液型金矿的主要依据。     

微波消解-电感耦合等离子体质谱法测定海泡石中的稀土元素

海泡石是一种纤维状含水的富镁硅酸盐黏土矿,其中的稀土元素含量在1×10~(-7)～1×10~(-5)之间,目前还没有建立海泡石中稀土元素的国家标准分析方法。测定岩石中的稀土元素主要是采用电感耦合等离子体质谱法(ICP-MS),样品前处理一般采用封闭溶矿和碱熔,但这两种处理方法耗时较长,效率不高。本文通过比较硝酸-氢氟酸-过氧化氢、硝酸-氢氟酸、硝酸-过氧化氢三种样品前处理方法,确定使用硝酸-氢氟酸溶矿,然后进行微波消解同时赶去氢氟酸,避免氢氟酸与稀土元素生成难溶的氟化物,再采用ICP-MS法测定15种稀土元素的含量。由于海泡石中的镁含量较高,为降低基体效应,以~(103)Rh和~(185)Re作内标补偿基体效应和校正灵敏度漂移,各元素测定值的准确性显著提高,回收率为91. 2%～110. 9%,检出限为0. 002～0. 011μg/L,精密度≤2. 79%。本方法与封闭酸溶ICP-MS法的分析结果吻合较好,且用酸量少(7 mL),溶矿效率高(1 h),检出限更低。     

辽东半岛大金山花岗岩体SHRIMP U-Pb年龄、元素地球化学和Hf同位素特征及地质意义

辽东半岛早白垩世时期受到强烈的构造—岩浆作用使岩石圈构造环境由挤压造山向伸展减薄转变,前人对其成因有所争议。本文通过锆石SHRIMP U- Pb测年、原位Lu- Hf同位素和主量、微量、稀土元素测试对辽东半岛大金山花岗岩体进行了系统研究,结果显示：大金山花岗岩体结晶年龄为~ 124Ma,侵位于早白垩世岩浆活动的高峰期。岩石地球化学特征显示大金山花岗岩属弱过铝质~过铝质岩石,经历了高程度的结晶分异过程,富集Rb、Th、U、K等大离子亲石元素（LILE）,亏损P、Ti等高场强元素（HFSE）,中等Eu负异常,为I型花岗岩。TW003样品εHf(t)值为-25.8~ -14.2,tDM2为2093~2805Ma,岩浆物质来源于新太古代—古元古代下地壳火成岩的部分熔融。根据年代学和岩石地球化学研究认为大金山花岗岩是古太平洋板块向欧亚大陆板块俯冲所形成的活动大陆边缘弧花岗岩,辽东半岛早白垩世的伸展环境是受板块俯冲造山后伸展作用和下地壳拆沉作用的联合制约。     

肥东杂岩的锆石U-Pb年龄及其地质意义——兼论下扬子地区新元古代岩浆活动历史

近年来在下扬子西缘地区厘定的一系列新元古代火成岩,为认识该区扬子板块新元古代岩浆活动历史与规律提供了窗口。结合本次与前人锆石U-Pb年代学数据,指示下扬子地区张八岭群、肥东杂岩与董岭杂岩内变火成岩的原岩时限分别为767~748 Ma、812~745 Ma和829~754 Ma。这些新元古代火成岩分别是峰期为750 Ma、800 Ma和825 Ma岩浆活动的产物。下扬子地区峰期为825 Ma的岩浆活动只出现在靠近江南造山带的南部。锆石年代学信息显示,下扬子地区还发生过峰期为840 Ma、2010 Ma和2454 Ma岩浆活动,但缺失1000~860 Ma的岩浆活动。通过区域对比表明,攀西—汉南弧没有延入下扬子地区。下扬子地区南部受到峰期为840 Ma的弧岩浆活动的影响。扬子板块上峰期为825 Ma的岩浆活动及早阶段的南华裂谷应是江南造山带后造山伸展的产物;而峰期为800 Ma和750 Ma的岩浆活动与相应的南华裂谷扩展,代表了Rodinia超大陆裂解的全面影响。     

华北板块南缘伏牛山花岗岩锆石LA-MC-ICP-MS U-Pb定年、Lu-Hf同位素特征及岩石成因

伏牛山花岗岩体出露于华北板块南缘,南召县城以北,面积超过4200km~2。岩体的岩石组合为花岗岩+花岗闪长岩+石英闪长岩,具有I型花岗岩的特征。花岗岩锆石的LA-MC-ICP-MS U-Pb定年得到145.4±1.0Ma和118.5±0.6Ma,说明岩体形成于燕山期,并经历了至少两期岩浆活动。锆石Hf同位素分析表明,第一期花岗岩的ε_(Hf)(t)平均值为-16.53,二阶段模式年龄(t_(DM2))平均为2216Ma,表明其源岩以壳源物质为主;第二期花岗岩的源岩分为两个部分,一部分花岗岩的ε_(Hf)(t)平均值为-13.67,二阶段模式年龄(t_(DM2))平均为2044Ma,表明其源岩以壳源物质为主,另一部分花岗岩的ε_(Hf)(t)平均值为1.61,二阶段模式年龄(t_(DM2))平均为1073Ma,表明其源岩以新生地壳为主。根据研究结果及区域地质构造分析,认为第一期岩浆作用是由于太平洋板块俯冲导致秦岭造山带断裂构造再活动,发生部分熔融形成小规模的岩浆作用;而第二期岩浆作用是由于太平洋板块俯冲导致岩石圈拆沉,使地幔软流圈的物质上升,形成巨大的热场,引起大陆地壳大规模的部分熔融形成花岗岩浆。最终形成的花岗岩浆沿着华北板块与扬子板块之间的断裂上侵至地壳浅处,形成了伏牛山复式岩体。     

藏南喜马拉雅造山带造山型马扎拉Au-Sb矿床和沙拉岗Sb矿床流体包裹体He-Ar同位素组成:对成矿流体来源的制约

马扎拉Au-Sb矿床和沙拉岗Sb矿床是藏南金锑成矿带中典型的造山型矿床。马扎拉Au-Sb矿床中矿体以含金辉锑矿石英脉的形式产于下中侏罗统陆热组地层中,主要组成矿物有自然金、辉锑矿、石英和碳酸盐矿物;沙拉岗Sb矿床中矿体主要以辉锑矿石英脉的形式产于下白垩统多久组地层和辉长岩体中,主要组成矿物为辉锑矿、辰砂、锑华、石英和少量碳酸盐矿物。在两个矿床的矿脉石英和辉锑矿中均发现有三类原生和假次生包裹体:水溶液包裹体、CO2-水溶液包裹体和有机包裹体。流体包裹体显微测温结果显示:马扎拉Au-Sb矿床的成矿温度为160～280℃,沙拉岗Sb矿床的成矿温度为140～240℃。He-Ar同位素分析显示马扎拉Au-Sb矿辉锑矿石英脉矿石中辉锑矿和石英以及赋矿地层中沉积层状硫化物中黄铁矿的流体包裹体均具有低的3He/4He比值,分别为0. 01382～0. 05642Ra和0. 03353～0. 08744Ra,40Ar/36Ar比值具有比较大的变化范围,分别为346. 8～4770. 1和349. 4～2689. 1;沙拉岗Sb矿床中辉锑矿样品的3He/4He比值为0. 02385～0. 11488Ra,40Ar/36Ar比值变化小,为300. 6～537. 5。与藏南Au-Sb成矿带中造山型Au矿床成矿流体中含一定量的幔源挥发份相对比,马扎拉AuSb矿床和沙拉岗Sb矿床成矿流体中均无幔源流体的参与,马扎拉Au-Sb矿床成矿流体为壳源变质流体与改造型饱和大气水形成的混合流体;沙拉岗Sb矿床成矿流体以改造型饱和大气水为主,并有壳源变质流体的加入。