Mineral chemistry of Plio-Quaternary subvolcanic rocks,southwest Yazd Province,Iran

The NW–SE-trendingLate Cretaceous–Cenozoic Urumieh-Dokhtar Magmatic Arc (UDMA) in southwest Iran hosts numerous Plio-Quaternary subvolcanic porphyritic andesitic to rhyodacitic domes intruded into a variety of rock sequences. Bulk-rock geochemical data show that the calc-alkaline dacitic to rhyodacitic subvolcanic rocks share compositional affinities with high-silica adakites, including high ratios of Na₂O/K₂O >1, Sr/Y (most >70), and La/Yb (>35), high Al₂O₃ (>15 wt.%), low Yb (<1.8 ppm) and Y (<18 ppm) contents, no significant Eu anomalies, and flat to gently upward-sloping chondrite-normalized heavy rare-earth element (HREE) patterns. All analysed rocks are characterized by enrichment in large-ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). They also display typical features of subduction-related calc-alkaline magmas. In chondrite-normalized rare-earth element patterns, the light rare-earth elements (LREEs) are enriched ((La/Sm) _N = 3.49–7.89) in comparison to those of the HREE ((Gd/Yb) _N = 1.52–2.38). Except for the G-Aliabad Dome, plagioclase crystals in the Shamsabad, Ostaj, Abdollah, and Bouragh Domes are mostly oligoclase to andesine (An_19–49). Amphibole and biotite are abundant ferromagnesian minerals in the subvolcanic rocks. Calcic amphiboles are dominantly magnesiohornblende, magnesiohastingsite, and tschermakite with Mg/(Mg + Fe_tot) ratios ranging from 0.58 to 0.78. In all the studied domes, amphiboles are typically ferric iron-rich, but that those the Shamsabad Dome have the highest Fe³⁺/(Fe³⁺ + Fe²⁺) ratios, between 0.69 and 0.98. Amphiboles from the Ostaj and Shamsabad Domes are relatively rich in F (0.39–1.01 wt.%) in comparison to the other studied domes. This phase commonly shows pargasitic and hastingsitic substitutions with a combination of tschermakitic and edenitic types.

Temperature-corrected Al-in-hornblende data show that amphibole phenocrysts from the Ostaj, Abdollah, and G-Aliabad Domes crystallized at pressures ranging from 2.14 to 3.42 kbar, 3.49 to 3.96 kbar, and 2.02 to 3.47 kbar, respectively. Temperatures of crystallization calculated with the amphibole–plagioclase thermometer for the Ostaj, Abdollah, and G-Aliabad subvolcanic domes range from 735°C to 826°C (mean = 786 ± 29), 778°C to 808°C (mean = 791 ± 13), and 866°C to 908°C (mean = 885 ± 12), respectively. In the annite–siderophyllite–phlogopite–eastonite quadrilateral, biotite from the G-Aliabad, Bouragh, and Ostaj Domes are characterized by relatively low total Al contents with variable Fe_tot/(Fe_tot + Mg) values from 0.26 to 0.43. All biotite analyses define a nearly straight line in the X _Mg versus Fe_tot plot, with r = –0.96 correlation coefficient. In comparison to other domes, the F content of biotite from the G-Aliabad Dome shows high concentrations in the range of 1.80–2.57 wt.% (mean = 2.20). Inferred pre-eruptive conditions based on the calcic amphibole thermobarometric calculations for the Shamsabad, Abdollah, and Ostaj Domes show that the calc-alkaline subvolcanic magma chamber, on average, was characterized by a water content of 6.10 wt.%, a relatively high oxygen fugacity of 10^–10.66 (ΔNNO + 1.28), a temperature of 896°C, and a pressure of 2.75 kbar.     

滇西高黎贡山南段奥陶纪花岗岩SHRIMP锆石 U-Pb测年和地球化学特征

在1∶5万马厂幅、道街坝幅区域地质调查工作的基础上,对高黎贡山南段的2个二长花岗质糜棱片麻岩样品所作的SHRIMP锆石U-Pb测年结果分别为（473.5±2.9）Ma和（461.5±7.3）Ma,属于中奥陶世侵入岩。岩石地球化学分析结果表明,岩石的SiO2、Al2O3、K2O含量高（SiO2=71.06%~73.88%,Al2O3=13.03%~14.27% ,K2O=2.81%~5.53%）,CaO含量低（CaO=0.67%~1.71%）,属于过铝质(AL/CNK=1.4~1.8)钙碱性岩;稀土元素Eu明显亏损(δEu=0.19~0.47);微量元素中Rb、Th相对富集,Ba相对亏损;Sm、Nd同位素分析结果：143Nd/144Nd为0.512022、0.512056。结合野外地质调查所作的综合研究认为该期花岗岩为壳源岩石,反映了泛非运动晚期冈瓦纳大陆北部陆－陆碰撞环境的岩浆活动。     

江苏及邻区震群活动特征分析

系统地整理研究了江苏及其邻近地区36次小震群活动,总结了震群活动的参数特征,探讨了震群活动与大震的关系,分析检验了前兆震群类型的判定指标.江苏地区震群活动分布集中,强度以ML2.0～3.9地震为主,震群序列总频次在30次以下居多,持续时间在15天以内的震群占总数的55％;震群序列中地震总频次和震群持续时间与震群的最大震级之间不成正比;研究区78％震群发生后对应M4.6以上中强地震,其中500km范围内时间间隔在1年内的占对应地震总数的57％,具有一定的中短期地震预测指示意义;震群与未来中强地震的距离较为离散,但尚无在原地发生大地震的震例.震群强度大小与未来中强地震的对应率高低和对应的地震强度大小没有明显的相关关系,震群频次的多少与其后发生地震的对应率高低也没有明显的相关关系.采用U-p组合或者全组合判定震群类型的效果相对较好,检验正确率约占总数的50％,但总体而言效果并不十分有效,需要参考其它方法和手段综合判定.     

Pseudofrenelopsis fossils from Cretaceous gypsum beds in Guixi,Jiangxi Province,China and their geological significance

Compressed fossil plants were found in the gypsum beds of the Zhoujiadian Formation in Guixi City, Jiangxi Province, China. The cuticular features of two species of Pseudofrenelopsis (Cheirolepidiaceae) were examined by scanning electron microscopy in this study: Pseudofrenelopsis papillosa Cao ex Zhou and Pseudofrenelopsis guixiensis Bainian Sun et Dai, sp. nov. A detailed analysis of the internode epidermis, and the adaxial and abaxial leaf cuticles of the two species, was performed, extending our knowledge of the morphological and anatomical characteristics of the extinct Pseudofrenelopsis. A new species, Pseudofrenelopsis guixiensis sp. nov., is proposed based upon comparison of its cuticular features. It differs from previously published species in that it has hairs on the abaxial surfaces of its leaves, sometimes shares subsidiary cells on the surfaces of internodes, lacks a hypodermis, and has no papillae on its epidermal cells. Because the distribution of fossil Pseudofrenelopsis is restricted to the Lower Cretaceous, the Early Cretaceous age of the Zhoujiadian Formation is affirmed. The fossils of Pseudofrenelopsis show obvious xeromorphic characteristics, such as apparent thickening of the cuticles, subsidiary cells with obvious papillae, and anticlinal walls with strong cutinization, and they are found associated with gypsum beds and close to red beds. All of these features indicate an arid climate.     

地球化学异常下限不同确定方法及合理性探讨

地球化学异常下限的确定对于圈定有利的成矿带,指导找矿非常关键.文章以甘肃省白银市白银矿区及外围水系沉积物Cu,Pb,Zn,Ag等4个元素为例,分别运用传统方法、归一化法和分形方法对数据进行处理.将3种方法圈定的异常进行比较发现:传统方法圈出的异常有限,主要是在矿区出现异常;而归一化法可以圈出更多的异常,并且与矿化集中区...     

蒙古国巴颜乌列盖多兰哈达地区地球化学特征及成矿

蒙古国巴颜乌列盖多兰哈达位于世界著名的铜—金—铅锌—钨金属成矿区—阿尔泰多金属成矿带北西段。区内出露地层主要为泥盆纪火山—沉积岩系。地球化学异常呈环带状分布,与岩体关系密切,该区铅锌矿为受火山通道控制的火山热液型金—铅锌矿床。矿区西部有寻找深部富矿体的前景,矿区南部及矿区东部次火山斑岩体附近,有寻找深部盲矿体的潜力。     

甘肃小陇山林区甘肃鼢鼠危害面积的气象预测预报技术研究

甘肃小陇山林区位于我国四大自然植被区系（华北、华中、喜马拉雅、蒙新）交汇处的温带向亚热带过渡带,林业植物种类繁多、茂密,但区内地形、地貌复杂,气候差异大,林业生物灾害频繁,环境气候条件是其发生发展的主要制约因素。为此,进行区内林业生物灾害的气象预测预报技术研究,对林业有害生物灾害的预防、防治和林业产业发展具有显著的指导...     

甘肃漳县马路里红柱石矿矿床地质特征及综合利用探讨

红柱石作为高级耐火材料,适用于冶金、建材、陶瓷等多种行业。甘肃省漳县马路里红柱石矿床是具有大型规模的矿床,矿体最大厚度42.77m,精矿品位达56%,耐火度大于1 830℃,累计探明资源量496.54万t。经国家非金属研究中心西北实验基地等多家单位科研人员的联合攻关,漳县红柱石精选试验获得成功,为大规模工业化生产铺平了...     

吉林省三所城市电磁辐射监测结果统计分析与评价

以城市环境电磁污染为研究对象,根据吉林省长春、延吉、四平环境综合电场强度监测数据．利用统计学方法和指数评价法进行统计分析和评价,计算了三所城市的电磁污染评价指数和污染风险概率,并对环境电磁辐射容量进行了估算。结果表明：目前三所城市环境电磁辐射电场强度监测值具有不同的概率分布,辐射强度低于中国电磁辐射安全标准,污染风险概率为0。如果电磁辐射能量以年均14％的速度递增,长春、延吉、四平将分别在19年、16年和18年后电磁辐射水平超过电磁环境保护限值,因此应该加强城市环境电磁辐射的管理和防控。     

河南省城市化水平综合评价及区域格局分析

根据城市化的内涵构建城市化水平综合评价指标体系,采用多目标决策TOPSIS法结合信息熵赋权法,对河南2001-2009年各地市的城市化水平进行综合评价分析;继而采用ESDA-GIS方法,对河南城市化综合水平的地域空间格局演化特征进行探讨。研究表明,河南各地市城市化综合水平虽然自2001年以来均获得了不同程度的提升,但地市间城市化水平的绝对差异和相对差异均呈拉大趋势;城市化热点地区在空间上表现出由集中分布向随机分布的演变态势,但整体上仍呈现出以中原城市群地区为核心的热点区和以外围地市为冷点区的核心—边缘型空间格局,由此认为着力推进边缘化传统农区的城市化进程是实现河南城市化区域协调发展的关键。