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171.
Chemistry of major and minor elements, 87Sr/86Sr, δD, δ18O and δ34S of brines were measured from Tertiary strata and Quaternary salt lakes in the western Qaidam Basin. The water chemistry
data show that all oilfield brines are CaCl2 type. They were enriched in Ca2+, B3+, Li+, Sr2+, Br−, and were depleted in Mg2+, SO4
2−, which indicated that these brines had the characteristics of deeply circulated water. The relationship between δD and δ18O shows that all data of these brines decline towards the Global Meteoric Water Line (GWL) and Qaidam Meteoric Water Line
(QWL), and that the intersection between oilfield brines and Meteoric Water Lines was close to the local spring and fresh
water in the piedmont in the western Qaidam Basin. The results suggest that oilfield brines has initially originated from
meteoric water, and then might be affected by water-rock metamorphose, because most oilfield brines distribute in the range
of metamorphosing water. The 87Sr/86Sr values of most oilfield brines range from 0.71121 to 0.71194, and was less than that in salt lake water (>0.712), but close
to that of halite in the study area. These imply that salt dissolution occurred in the process of migration. In addition,
all oilfield brines have obviously much positive δ34S values (ranging from 26.46‰ to 54.57‰) than that of salt lake brines, which was caused by bacterial sulfate reduction resulting
in positive shift of δ34S value and depleteed SO4
2− in oilfield brines. Combined with water chemical data and δD, δ18O, 87Sr/86Sr, δ34S values, we concluded that oilfield brines mainly originate from the deeply circulated meteoric waters, and then are affected
by salt dissolution, water-rock metamorphose, sulfate reduction and dolomitization during the process of migration. These
processes alter the chemical compositions of oilfield brines and accumulate rich elements (such as B, Li, Sr, Br, K and so
on) for sustainable utilization of salt lake resources in the Qaidam Basin. 相似文献
172.
针对北秦岭丹凤地区产铀花岗岩的区域地层、赋矿围岩、蚀变岩和铀矿石进行稀土元素地球化学研究,结果表明:各类样品具有大体类似的LREE富集及Eu负异常的稀土配分模式,表明它们之间稀土元素特征具有继承性;赋矿黑云母二长花岗岩与区域地层(丹凤岩群变质基性火山岩)稀土元素特征指示,二者均形成于岛弧环境;蚀变花岗岩和铀矿石主要继承了赋矿花岗岩的特征。各类样品Y/Ho值变化范围狭窄,为25.09~33.46,显示它们具有共同的源区。铀矿石具有最高的wB(∑HREE),且与铀矿石的品位存在正相关关系,暗示HREE与铀的迁移具有同步性。 相似文献
173.
针对用均匀高阻介质中的低阻体来模拟含水岩溶构造的缺陷,用积分方程法对两层介质中的岩溶构造进行了数值模拟,并分析了计算曲线的特征,以及表层、岩溶与围岩的电阻率差异对探测结果的影响。计算结果对野外施工和资料解释具有指导意义。 相似文献
174.
相山及邻区七个火山盆地火山岩岩性特征及成因探讨 总被引:4,自引:0,他引:4
本文研究赣杭构造带西南端相山及其邻区7个火山盆地主体岩石的特征和成因,从地质产状、岩性、岩石化学等方面做了论述。采用了红外光谱、矿物包裹体、高温实验等研究方法,探讨了岩石的形成机理。相山主体岩石是一种成因特殊的火山碎屑(斑)熔岩,即岩颈碎屑熔岩和岩流碎屑熔岩。相山等火山盆地主体岩石边部的塑性岩屑不是熔离成因,而是由火山喷发作用形成的。火山碎屑熔岩中的斜长石牌号变化大,钾长石主要是低透长石,表明岩石的形成具有高温特征。不同岩石相的矿物中的熔融包裹体有明显的形态标型。碎眉熔岩中的石英碎斑结构,主要是高温热炸裂成因的。7个火山盆地中的主体岩石可划分两大类:相山、玉华山和礼陂火山盆地的主体岩石是火山碎屑熔岩;高家、林家、谙源和谭港火山盆地的主体岩石是弱熔结凝灰岩。 相似文献
175.
CH4 inclusions in orogenic harzburgite: Evidence for reduced slab fluids and implication for redox melting in mantle wedge 总被引:3,自引:0,他引:3
Fluids released from the subducting oceanic lithosphere are generally accepted to cause mantle wedge peridotite melting that produces arc magmas. These fluids have long been considered to be dominated by highly oxidized H2O and CO2 as inferred from erupted arc lavas. This inference is also consistent with the geochemistry of peridotite xenoliths in some arc basalts. However, the exact nature of these fluids in the mantle wedge melting region is unknown. Here, we report observations of abundant CH4 + C + H2 fluid inclusions in olivine of a fresh orogenic harzburgite in the Early Paleozoic Qilian suture zone in Northwest China. The petrotectonic association suggests that this harzburgite body represents a remnant of a Paleozoic mantle wedge exhumed subsequently in response to the tectonic collision. The mineralogy, mineral compositions and bulk-rock trace element systematics of the harzburgite corroborate further that the harzburgite represents a high-degree melting residue in a mantle wedge environment. Furthermore, existing and new C, He, Ne and Ar isotopes of these fluid inclusions are consistent with their being of shallow (i.e., crustal vs. deep mantle) origin, likely released from serpentinized peridotites and sediments of the subducting oceanic lithosphere. These observations, if common to subduction systems, provide additional perspectives on mantle wedge melting and subduction-zone magmatism. That is, mantle wedge melting may in some cases be triggered by redox reactions; the highly reduced (∼ΔFMQ-5, i.e., 5 log units below the fayalite-magnetite-quartz oxygen fugacity buffer) CH4-rich fluids released from the subducting slab interact with the relatively oxidized (∼ΔFMQ-1) mantle wedge peridotite, producing H2O and CO2 that then lowers the solidus and incites partial melting for arc magmatism. The significance of slab-component contribution to the geochemistry of arc magmatism would depend on elemental selection and solubility in highly reduced fluids, for which experimental data are needed. We do not advocate the above to be the primary mechanism of arc magmatism, but we do suggest that the observed highly reduced fluids are present in mantle wedge peridotites and their potential roles in arc magmatism need attention. 相似文献
176.
Geochemical Features of Ophiolite in Mianxian Lueyang Suture Zone,Qinling Orogenic Belt 总被引:10,自引:0,他引:10
GeochemicalFeaturesofOphioliteinMianxianLueyangSutureZone,QinlingOrogenicBeltLaiShaocong;ZhangGuowei(DepartmentofGeology,Nort... 相似文献
177.
178.
乳砷铅铜石的发现与研究 总被引:2,自引:0,他引:2
乳砷铅铜石发现于1984年,在广西德保和平桂等矿区的硫化物型矿床的氧化带铁帽中.对该矿物的物理、化学和X射线粉晶分析、红外光谱分析以及差热分析等方面进行了测试研究,其结果与国外已知数据基本一致.矿物呈淡黄绿或深绿色,细粒状或葡萄状,硬度H=4,比重D=5.35,透明,二轴晶负光性,2V大,Ng=1.9817,Nm=1.9703,NP=1.9584.化学成分为PbO 35.19,CuO 30.64,As_2O_5 30.09,FeO 0.28,ZnO 0.05,H_2O 4.10(%).相应的化学分子式为Cu_(2.96)Pb_(1.21)(AsO_4)_(2.01)(OH)_(2.31)·0.59H_2O.X射线粉晶数据与JCPDS26~1410卡基本一政,衍射强线为3.14(10),3.24(8),2.92(8),2.55(8),2.74(7),2.49(7),2.27(7),4.51(6),4.94(5),2.66(4),1.902(4),1.817(4).计算的晶胞参数为a=10.236(?).b=5.904(?),C=14.213(?),β=106.39°,z=4,单斜晶系;空间群为A2/a.红外吸收光谱波数为3440、1640、870、820、775、465和1100、590、557(cm~(-1));差热分析吸收峰为580、773、812、889、898(℃). 相似文献
179.
基于CMIP5模式的中国气候变化敏感性预估与分析 总被引:4,自引:0,他引:4
以CMIP5提供的26个全球气候系统模式的温度和降水数据为基础,采用区域气候变化指数(Regional Climate Change Index,RCCI)分析中国的不同区域对21世纪气候变化响应的敏感性。结果表明,三种排放情景(RCP 2.6、RCP 4.5、RCP 8.5)下,21世纪全期,气候变化最敏感的区域分布在西藏地区,其次为我国西北地区以及东北地区,气候变化敏感性最低的区域分布在我国内蒙古中东部、华北地区以及长江中下游一带,且高排放情景对应更高的气候变化敏感性。对RCCI指数贡献因子分析结果表明,对中国气候变化敏感性贡献的大小依次为Δσ_TΔσ_pΔRRWAF。冬夏两季温度变化的大值区与RCCI指数的大致区分布一致,RCCI大小的分布很大程度上由温度变化的敏感性决定。而夏季降水变化的大值区主要出现在西藏地区、华南地区和东北地区,冬季降水变化的大值区则主要出现在黄河以南长江以北的中原地区以及东北地区。 相似文献
180.
利用场地误差优化模式对深圳地区的地闪定位资料进行优化处理。首先对深圳市闪电定位系统进行简单介绍,然后利用改进的传输线模式对真实地表环境下的闪电辐射电磁场进行计算,以分析深圳市闪电定位系统的场地误差,最后基于定位误差和场地误差模式对闪电定位数据进行定位误差订正。结果表明不同方位角上的不规则地形对继后回击电磁场波形具有不同影响,随着表征地形粗糙程度的高度均方根的增加,电场的峰值下降,波形的上升沿时间增加。同时,电场波形上升沿时间也会随着方位角的变化而变化,这可能会给时间到达法的定位带来一定误差。为了验证该算法的合理性,对该系统覆盖的区域进行了闪电定位数据优化精度的时空分布分析和评估。结果表明这种优化方案是可行的、可靠的,优化后的闪电定位精度明显提高。 相似文献