Disparities in Prevalence and Determinants of Hypertension amongst Bamiléké Adults Residing in Two Different Agroecological Zones of Cameroon

Background: Cardiovascular diseases such as hypertension (HTN) are one of the main causes of death in Cameroon. This study aimed at assessing prevalence disparities and determinants of hypertension amongst Bamiléké adults residing in two different agroecological zones of Cameroon. Methods: A cross-sectional and descriptive survey was conducted among Bamiléké population living in the Highlands zone (Western region) and in the Monomodal Rainforest zone (Littoral region) of Cameroon from August 2016 to August 2017. Participants (962) were aged at least 20 years old. Data on sociodemographic, hemodynamic, anthropometric, and biochemical parameters and lifestyle of the participants were collected. Results: Results obtained revealed that 34.2% were hypertensive and those residing in the highland zone were more affected than those living in the monomodal rainforest zone (44.5% vs 22.9%). The different subtypes of HTN (Isolated systolic hypertension (14.1%), isolated diastolic hypertension (7.2%) and Systo-diastolic hypertension (23.3%)) were also more prevalent in the Highlands Zone. The most prevalent stage of HTN was pre-HTN (31.5%). However, people living in the monomodal rainforest zone were more affected by pre-HTN compared to Bamiléké living in the highland zone (33.6% vs. 29.6%). Results also showed that high consumption (≥ 3 times/week) of carbohydrate- and fat-rich foods, ageing, obesity, and marital status were associated with high blood pressure in both agroecological zones. Besides, secondary education (OR = 0.68;95% CI: 0.42 - 0.99) in the Highlands Zone and high (≥3 times/week) vegetable consumption (OR = 0.66;95% CI: 0.44 - 0.98) in the Monomodal Rainforest Zone had a protective effect on elevated blood pressure of population. Conclusion: There is a disparity in the prevalence of hypertension and some of its determinants among Bamiléké adults residing in different agroecological zones. This work highlights the need to advocate for local and ethno-cultural health policies to prevent, diagnose and manage hypertension.

Mechanical mechanism of overlying strata breaking and development of fractured zone during close-distance coal seam group mining

This study mainly investigates the mechanical mechanism of overlying strata breaking and the development of fractured zones during close-distance coal seam group mining in the Gaojialiang coal mine.First,a mechanical model for the second"activation"of broken overlying strata is established,and the related mechanical"activation"conditions are obtained.A recursive formula for calculating the separation distance of overlying strata is deduced.Second,a height determining method for predicting the height of fractured zones during close-distance coal seam group mining is proposed based on two values,namely,the separation distance and ultimate subsidence value of overlying strata.This method is applied to calculate the fractured zone heights in nos.20107 and 20307 mining faces.The calculated results are almost equal to the field observation results.Third,a modified formula for calculating the height of a waterflowing fractured zone is proposed.A comparison of the calculated and observed results shows that the errors are small.The height determining method and modified formula not only build a theoretical foundation for water conservation mining at the Gaojialiang coal mine,but also provide a reference for estimating the height of water-flowing fractured zones in other coal mines with similar conditions.

磁共振表观扩散系数鉴别诊断移行带高危前列腺癌及与病理分级分组的相关性

目的探讨磁共振扩散加权成像(diffusion-weighted imaging,DWI)的表观扩散系数(apparent diffusion coefficient,ADC)值和相对ADC值对移行带高危前列腺癌(high-risk prostate cancer,hPCa)的鉴别诊断价值及与国际泌尿病理学会(International Society of Urological Pathology,ISUP)前列腺癌分级分组(grading group,GG)的相关性。材料与方法回顾性分析经病理证实的40例移行带前列腺癌患者的双参数MRI资料,分别测量移行带癌灶和基质型增生结节的平均ADC(mean ADC,ADC_(mean))值和最小ADC(minimum ADC,ADC_(min))值,并计算移行带癌灶与基质型增生结节ADC比值的相对ADC_(mean)(relative ADC_(mean),rADC_(mean))值和相对ADC_(min)(relative ADC_(min),rADC_(min))值。比较hPCa组与低危前列腺癌(low-risk prostate cancer,lPCa)组之间ADC_(mean)、ADC_(min)、rADC_(mean)和rADC_(min)值的差异。绘制受试者工作特征(receiver operating characteristic,ROC)曲线评估ADC各参数对移行带hPCa的诊断效能,并根据约登指数确定最佳截断值。采用DeLong检验比较ROC曲线下面积(area under the curve,AUC)的差异。Spearman相关分析ADC各参数与ISUP GG之间的相关性。结果hPCa组的ADC_(mean)、ADC_(min)、rADC_(mean)和rADC_(min)值均低于lPCa组(P均<0.05)。ADC_(mean)、ADC_(min)、rADC_(mean)和rADC_(min)鉴别诊断移行带hPCa的AUC分别为0.775[95%置信区间(confidence interval,CI):0.615~0.892]、0.879(95%CI:0.736~0.960)、0.751(95%CI:0.589~0.874)和0.914(95%CI:0.782~0.979),rADC_(min)的AUC最大。rADC_(min)与ADC_(mean)和rADC_(mean)的AUC差异均有统计学意义(P均<0.05),但与ADC_(min)的AUC差异无统计学意义(P>0.05)。当rADC_(min)最佳截断值取0.664×10^(-3)mm^(2)/s,约登指数最大(0.783),诊断移行带hPCa的敏感度和特异度分别为100.00%、78.26%。ADC_(mean)、ADC_(min)、rADC_(mean)和rADC_(min)值与ISUP GG均呈负相关[r=-0.486(95%CI:-0.755~-0.151)、-0.613(95%CI:-0.769~-0.365)、-0.553(95%CI:-0.745~-0.260)、-0.678(95%CI:-0.810~-0.474),P均≤0.001]。结论rADC_(min)鉴别诊断移行带hPCa的效能高,并且能够无创预测移行带PCa的ISUP GG,有助于为患者的个性化治疗决策提供支持。

基于网络群组特征的生态管理分区--以武汉市为例

生态管理分区是维持区域生态安全、实现城市生态差异化治理的重要手段。然而现有分区方法侧重生态功能属性,较少考虑生态斑块之间联系强度差异,忽视了斑块的群组结构。以武汉市为例构建生态网络,从生态系统结构和功能的视角,结合斑块空间组织和斑块联系强弱,运用凝聚子群方法,提取联系紧密的生态组分,将网络划分为异质性群组,基于网络群组特征和生态景观辐射范围进行分区覆盖分析,并进行分区评价。结果表明:(1)86条生态廊道连接研究区34处生态斑块,进一步形成8个生态群组;(2)多数群组内部连通性较好,北部群组之间联系较强,南部群组之间联系相对较弱;(3)依据群组结构功能特征,形成6大网络群组分区,通过与武汉市经济发展规划分区对比,两者具有较高的一致性;(4)城市外围的分区网络稳定性较好,中部稳定性较差,识别分区内13个重要斑块和16条重要廊道,作为重点发展保护对象;(5)综合分区特征将6大分区确立为生态屏障区、生态控制区、生态改善区、生态修复区、生态开发区以及生态保育区,并提出生态发展差异化保护措施。研究将生态功能属性和空间结构属性进行有机关联并制定分区策略,为区域生态管理分区、生态保护规划提供新视角。

川东地区高陡构造带寒武系洗象池群天然气成藏条件

利用岩心、测井与地震资料,采用地震解释、平衡剖面以及包裹体检测等技术,恢复了川东地区高陡构造带的构造演化史,并对平桥、建南、梓里场构造的天然气来源、运聚与保存条件进行了分析。研究结果表明:(1)川东地区平桥断背斜圈闭东翼的单条逆断层使得下盘的龙马溪组烃源岩与上盘的洗象池群储层发生了侧向对接,天然气可穿过断裂带向上盘储层运移,具备较好的输导条件,且圈闭盖层未受到断裂作用破坏,保存条件良好,有利于天然气的聚集成藏。(2)建南断背斜圈闭翼部的多条平行的逆断层虽然实现了部分源-储对接,但是多条断层组合降低了其侧向输导能力,天然气未能大规模聚集。(3)梓里场断背斜圈闭的源-储配置与输导条件优良,但盖层的封盖能力较差,大多被断层破坏,钻探显示储层为水层。(4)川东地区高陡构造带寒武系洗象池群天然气聚集成藏的主控因素包括:断层或断层组合控制下的源-储配置、侧向输导条件以及盖层的封盖能力。

基于风环境优化的岭南高校教学组团形态布局设计研究

校园形态与环境舒适性的关系是校园建设的热门议题。探讨高校公共教学组团布局类型及关键设计要素与风环境评价指标的关系,目的在于为风环境导向下的公共教学组团空间形态控制提供思考路径。选取岭南地区54所建成高校公共教学组团作为研究对象,归纳总结组团布局类型,分析风环境相关设计要素(包括建筑朝向、建筑间距与围合形式),抽象高校公共教学组团理想模型,运用Phoenics软件进行夏季风环境模拟;设计单因子变量实验,分析不同因素与室外风环境的关联关系;对3个设计要素进行关联分析,探讨不同设计制约条件下的最优因素水平组合。结果显示,行列式布局在4种布局类型中室外风环境表现最优;当建筑根据地形呈斜向行列式布局时,组团室外风环境舒适性和空间感受较好;建筑间距与组团室外风环境呈正相关关系,但差异性较小;呈E型或S型围合的组团布局模式,连接体采用架空、挖洞等手法进行通透性处理,是兼顾室外风环境舒适性与空间需求的较优组团形式。

考虑频率死区的储能单元协同控制策略

新能源并网比例的不断攀升降低了电力系统惯量,导致系统调频能力下降。为此,开展了储能参与调频的研究。储能参与调频受到单元数量、荷电状态(state of charge,SOC)、充放电策略等因素影响,提出一种考虑频率死区的储能单元协同控制策略,根据SOC一致性对储能单元进行分组,不同组别单独执行下垂控制或虚拟惯量控制,简化出力控制指令。依据系统频率偏差或频率变化率进行控制指令切换,并分别设置频率偏差和频率变化率死区,以减少小扰动干扰导致储能系统频率充放电。基于Matlab/Simulink进行仿真验证,结果表明:所提控制策略简单便于执行,能够快速响应调频需求,并且能保证储能电池使用寿命。

大同火山群及邻区中小地震重定位

文中基于中国地震台网中心在大同火山群及周边地区记录到的2008年1月-2023年1月期间3 218个地震的到时资料,采用双差地震重定位法开展了重新定位研究,获得了2 447个事件的重定位结果。结果显示,地震大多发生在16km深度以浅处,集中分布于断陷盆地内及盆地边界的断裂带附近,整体走向NE-SW,与区域活动构造的活动断裂及其控制的地堑、半地堑型断陷盆地的走向较为一致。这些地震E-W向、S-N向、垂直向的平均定位误差约为0.21km、0.22km、0.30km,平均均方根残差为0.14s。口泉断裂带附近的地震分布由南部的较深、较集中变化为北部的较浅、较分散,可能与矿山开采活动有关。大同-阳高地震震源区的地震多集中在与大王村断裂平行的东侧隐伏断层的3~16km深度处,该隐伏断层与团堡断裂和六棱山山前断裂交会,可能与大同-阳高地震的余震活动有关。火山区内部的地震活动并不强烈。结合该区域新的背景噪声层析成像结果分析发现,大多数地震发生在低速异常边界,可能暗示了这些地震的发生与热物质上涌所携带的流体上升至地壳深度,进而降低断面有效正应力密切相关。

谱系群分析法在洮河大夏河流域水资源区划分中的分析应用

洮河大夏河流域位于黄河流域第一阶梯东部边缘一隅,属第一阶梯向第二阶梯的过渡地带。水资源时空分布在一定范围内的相似性就是变化与联系相互制约的结果。在洮河大夏河区域内选择15个降水量代表站,各站组合计算相关系数,然后采用逐次形成法依次进行连接合群,相关系数在一定置信水平下的临界值作为水资源区划群的划分参照。经区域站点相关性分析计算和流域对照,相关站点降水量呈现较好的相关性,计算的分区能较好的反映区域内各分区的降水量特点,与当地的降水特性,地形地貌及成雨条件吻合度较高,对水资源分区与计算提供了可行可操作的分析方法。

近距离煤层群隔层“探、治”瓦斯技术体系研究及应用

为解决贵州地区近距离复杂群层群采掘过程中邻近煤层瓦斯防治难题,提出了包括邻近煤层瓦斯参数探查技术、保护层开采上覆岩层“三带”范围考察技术和邻近煤层瓦斯抽采防治技术的隔层“探、治”瓦斯技术体系。该技术体系在安顺煤矿的应用结果表明:M9煤层工作面采空区冒落带和裂隙带高度分别约为3.8 m和15.7 m,能够有效增益上覆M8煤层瓦斯治理;临近煤层瓦斯抽采效果受到抽采孔空间位置、长度和工作面推进情况影响,高位钻场、高位巷、高位定向长钻孔和密集穿层高位钻孔抽采方式的抽采纯量分别能达到12、37.7、10.0、40.1 m^(3)/min,高位巷和密集穿层高位钻孔抽采效果更优。研究成果为贵州地区煤层群瓦斯高效治理提供了理论和工程实践基础。

山西转型综改示范区实现高质量发展路径研究——基于“一群两区三圈”区域发展战略布局的思考

改革开放以来,山西逐渐形成了资源型经济发展模式,该模式之下发展瓶颈日趋凸显,为了实现更高质量发展,山西转型综改示范区应运成立。山西省第十二次党代会提出打造“一群两区三圈”的区域格局,这为山西转型综改示范区更好地引领辐射带动省内其他区域提出了更高的要求。示范区成立以来,发展的瓶颈也日趋凸显,如营商环境有待优化、产业链条有待延伸、发展空间有待拓展、产业化发展快于城镇化等。针对这些问题,文章从构建创新生态、打造“规划—考评—协调”的产业发展引导体系、发挥比较优势发展“飞地经济”、产城融合助力产城一体化高质量发展四个方面着力推动实现转型综改示范区高质量发展。

闽北太阳山金矿外围麻源群第三段下部土壤地球化学分区的作用

福建省建阳市太阳山金矿是闽北具有代表性的金矿点,矿区出露的主要地层属新元古界麻源群第三段下部,麻源群第三段第二岩性带是金的矿源层和赋矿层位。通过太阳山金矿及周边矿点资料数据和采矿区外围1:1万土壤地球化学测量土壤样品Au含量数据分析,发现麻源群第三段下部各地质单元Au含量在地层层序上存在“低-高-低”异常分布的规律性。以有限出露的基岩岩石组合类型为基础并结合Au在土壤中的分布异常、石墨矿物分布特征、地貌特征和少量地质工程验证等进行土壤地球化学分区,辅助划分了麻源群第三段第二岩性带与上覆和下伏地质单元的界线。

浅埋近距煤层群开采覆岩三带发育特征分析

研究浅埋近距离煤层群开采的覆岩三带规律对于指导矿井下行安全开采有着至关重要的作用。为了研究上、下煤层开采过程中覆岩层的破坏规律,根据韩家湾煤矿现场实际情况,通过物理相似模拟实验研究浅埋近距离煤层过上层煤的采空区时上覆岩层结构失稳特征。研究浅埋近距离煤层群条件下开采4-2煤层后的覆岩移动变形规律、裂隙发育规律、矿压变化规律及其随工作面推进的变化情况及地表岩层的运移规律,发现浅埋近距离煤层下组煤层回采过程中,上覆岩层下沉量呈现三阶段变化,即下沉量上升阶段、下沉量恒定不变阶段、下沉量减小阶段。距离下组煤层越近,覆岩下沉量越大,距离下组煤层越远,覆岩下沉量越小。明确覆岩三带发育特征,能够为浅埋近距离煤层群开采水害防治提供依据,为榆神府矿区类似重复采动时工作面的安全回采提供指导和借鉴。

近距离煤层群覆岩裂隙带瓦斯治理措施优化及效果分析

为解决近距离煤层群综采工作面回采中上隅角瓦斯治理难题,保障综采工作面有效衔接,实现连续安全高效生产,利用同位素测定分析技术明确了近距离煤层群卸压瓦斯涌入覆岩裂隙带内的规律特征,提出施工地面L型钻孔以优化原有的覆岩裂隙带瓦斯治理技术,降低综采工作面上隅角瓦斯体积分数。结果表明:屯兰矿2号煤层综采工作面的覆岩裂隙带高度附近,工作面自切眼回采的95 m范围内,02号煤卸压瓦斯抽采占比逐渐降低,2号和4号煤层的卸压瓦斯抽采占比逐渐升高,95 m后,02、2和4号煤卸压瓦斯抽采占比趋于稳定,占比分别为60%、25%和10%.优化后的“以孔代巷”技术“高位钻孔+低位钻孔+高位走向长钻孔+地面L型钻孔”将上隅角平均瓦斯体积分数由0.65%降低至0.25%.地面L型钻孔的施工在空间和时间上保障了井下综采工作面的连续稳定生产,对井下工程不形成干扰,有助于解决上隅角瓦斯超限问题,实现了综采工作面的安全高效连续生产。

Response of ants to grazing disturbance at the central Monte Desert of Argentina: community descriptors and functional group scheme

Livestock ranching is one of the main productive activities in arid regions of the world.Grazing produces changes in animal as well as plant communities(e.g.richness,abundance and species dominance relationships).Ants are good biological indicators due to the environmental fidelity of some of their community parameters.We described the functional structure of the ant community in the central Monte of Mendoza,Argentina,and examined the effect of grazing using richness,diversity and the functional group scheme.We used pitfall traps to sample ants at a reserve with 30-year cattle exclusion and at an adjacent ranch.Eleven of the 27 recorded species showed significant differences in their abundance and two species were absent at the ranch.While richness and diversity did not reflect these differences,functional groups did.Hot Climate Specialists were more abundant at the ranch while Cryptic Species and Generalized Myrmicinae increased at the reserve.This study supports the utility of the functional group scheme to study the effects of grazing disturbance in ant communities of arid regions.

A new understanding of Demala Group complex in Chayu Area, southeastern Qinghai- Tibet Plateau: Evidence from zircon U-Pb and mica ^(40)Ar/^(39)Ar dating

The Chayu area is located at the southeastern margin of the Qinghai-Tibet Plateau.This region was considered to be in the southeastward extension of the Lhasa Block,bounded by Nujiang suture zone in the north and Yarlung Zangbo suture zone in the south.The Demala Group complex,a set of high-grade metamorphic gneisses widely distributed in the Chayu area,is known as the Precambrian metamorphic basement of the Lhasa Block in the area.According to field-based investigations and microstructure analysis,the Demala Group complex is considered to mainly consist of banded biotite plagiogneisses,biotite quartzofeldspathic gneiss,granitic gneiss,amphibolite,mica schist,and quartz schist,with many leucogranite veins.The zircon U-Pb ages of two granitic gneiss samples are 205±1 Ma and 218±1 Ma,respectively,representing the ages of their protoliths.The zircons from two biotite plagiogneisses samples show core-rim structures.The U-Pb ages of the cores are mainly 644–446 Ma,1213–865 Ma,and 1780–1400 Ma,reflecting the age characteristics of clastic zircons during sedimentation of the original rocks.The U-Pb ages of the rims are from 203±2 Ma to 190±1 Ma,which represent the age of metamorphism.The zircon U-Pb ages of one sample taken from the leucogranite veins that cut through granitic gneiss foliation range from 24 Ma to 22 Ma,interpreted as the age of the anatexis in the Demala Group complex.Biotite and muscovite separates were selected from the granitic gneiss,banded gneiss,and leucogranite veins for 40Ar/39Ar dating.The plateau ages of three muscovite samples are 16.56±0.21 Ma,16.90±0.21 Ma,and 23.40±0.31 Ma,and the plateau ages of four biotite samples are 16.70±0.24 Ma,16.14±0.19 Ma,15.88±0.20 Ma,and 14.39±0.20 Ma.The mica Ar-Ar ages can reveal the exhumation and cooling history of the Demala Group complex.Combined with the previous research results of the Demala Group complex,the authors refer that the Demala Group complex should be a set of metamorphic complex.The complex includes not only Precambrian basement metamorphic rock series,but also Paleozoic sedimentary rock and Mesozoic granitic rock.Based on the deformation characteristics,the authors concluded that two stages of the metamorphism and deformation can be revealed in the Demala Group complex since the Mesozoic,namely Late Triassic-Early Jurassic(203–190 Ma)and Oligocene–Miocene(24–14 Ma).The early stage of metamorphism(ranging from 203–190 Ma)was related to the Late Triassic tectono-magmatism in the area.The anatexis and uplifting-exhumation of the later stage(24–14 Ma)were related to the shearing of the Jiali strike-slip fault zone.The Miocene structures are response to the large-scale southeastward escape of crustal materials and block rotation in Southeast Tibet after India-Eurasia collision.

Platinum-Group Elements Geochemistry and Chromian Spinel Composition in Podiform Chromitites and Associated Peridotites from the Cheshmeh-Bid Deposit, Neyriz, Southern Iran: Implications for Geotectonic Setting

Dunite and serpentinized harzburgite in the Cheshmeh-Bid area, northwest of the Neyriz ophiolite in Iran, host podiform chromitite that occur as sehlieren-type, tabular and aligned massive lenses of various sizes. The most important chromitite ore textures in the Cheshmeh-Bid deposit are massive, nodular and disseminated. Massive chromitite, dunite, and harzburgite host rocks were analyzed for trace and platinum-group elements geochemistry. Chromian spinel in chromitite is characterized by high Cr#（0.72-0.78）, high Mg#（0.62-0.68） and low TiO2 （0.12 wt%-0.2 wt%） content. These data are similar to those of chromitites deposited from high degrees of mantle partial melting. The Cr# of chromian spinel ranges from 0.73 to 0.8 in dunite, similar to the high-Cr chromitite, whereas it ranges from 0.56 to 0.65 in harzburgite. The calculated melt composition of the high-Cr chromitites of the Cheshmeh-Bid is 11.53 wt%-12.94 wt% A1203, 0.21 wt%-0.33 wt% TiO2 with FeO/MgO ratios of 0.69-0.97, which are interpreted as more refractory melts akin to boninitic compositions. The total PGE content of the Cheshmeh-Bid chromitite, dunite and harzburgite are very low （average of 220.4, 34.5 and 47.3 ppb, respectively）. The Pd/Ir ratio, which is an indicator of PGE fractionation, is very low （0.05- 0.18） in the Cheshmeh-Bid chromitites and show that these rocks derived from a depleted mantle. The chromitites are characterized by high-Cr#, low Pd ＋ Pt （4-14 ppb） and high IPGE/PPGE ratios （8.2- 22.25）, resulting in a general negatively patterns, suggesting a high-degree of partial melting is responsible for the formation of the Cheshmeh-Bid chromitites. Therefore parent magma probably experiences a very low fractionation and was derived by an increasing partial melting. These geochemical characteristics show that the Cheshmeh-Bid chromitites have been probably derived from a boninitic melts in a supra-subduction setting that reacted with depleted peridotites. The high-Cr chromitite has relatively uniform mantle-normalized PGE patterns, with a steep slope, positive Ru and negative Pt, Pd anomalies, and enrichment of PGE relative to the chondrite. The dunite （total PGE = 47.25 ppb） and harzburgite （total PGE =3 4.5 ppb） are highly depleted in PGE and show slightly positive slopes PGE spidergrams, accompanied by a small positive Ru, Pt and Pd anomalies and their PdJIrn ratio ranges between 1.55-1.7and 1.36-1.94, respectively. Trace element contents of the Cheshmeh-Bid chromitites, such as Ga, V, Zn, Co, Ni, and Mn, are low and vary between 13-26, 466-842, 22-84, 115- 179, 826-1210, and 697-1136 ppm, respectively. These contents are compatible with other boninitic chromitites worldwide. The chromian spinel and bulk PGE geochemistry for the Cheshmeh-Bid chromitites suggest that high-Cr chromitites were generated from Cr-rich and, Ti- and Al-poor honinitic melts, most probably in a fore-arc tectonic setting related with a supra-subduction zone, similarly to other ophiolites in the outer Zagros ophiolitic belt.

Geochemistry of platinum-group elements in the podiform chromitites and associated peridotites of the Nain ophiolites,Central Iran:Implications for geotectonic setting

The Nain ophiolite complex with an extent of[600 km2 is a part of the Central Iranian ophiolite,which is related to the opening and subsequent closure of the Neo-Tethys Ocean.Dunite and serpentinized harzburgite in the Nain area host podiform chromitites that occur as three(eastern Hajhossein,western Hajhossein,and Soheil Pakuh)schlieren-type tabular and aligned massive lenses with various sizes.The most common chromitite ore textures are massive,nodular,disseminated,and banded,reflecting crystal settling processes.The Cr#[Cr/(Cr+Al)]ranges from 0.43 to 0.81(average 0.63).The Mg#[Mg/(Mg+Fe2+)]varies from 0.25 to 0.78(average0.62).The Nain ophiolite and hosted chromitite are generally characterized by high Cr#,reflecting crystallization from a very hot boninite magma in a MORB setting.The high Cr#in the Nain chromitite also indicates a high degree of melting(15%–35%)of the depleted peridotite.The average total PGE content in the ophiolitic host rock(harzburgite and dunite)and chromite are 107 and 221 ppb,respectively.The Nain ophiolite and chromitite have high IPGE/PPGE and negative Pt*(Pt/Pt*=0.6)anomaly,which is a characteristic of high Cr#chromitite.The U-shaped REE pattern of dunite host rock suggests the interaction of depleted mantle peridotite with boninitic melt.Geochemical data suggest that the Nain chromitites are related to the boninitic magma emplacement in a suprasubduction zone.

Stability Assessment of Open Stope under Overlaying Mined-Out Regions at Modi Taung Gold Mine, Myanmar

Stability assessment is one of the most important issues in mining ground control. Mine development and/or production instability can cause production delay, loss of reserves, as well as injury to miners. Within the scope of this study, a series of open stope’s instability under the influence of overlaying mined-out regions were carried out with different mining scenarios at Modi Taung gold mine which is operated by National Prosperity Gold Production Group Limited (NPGPGL) in Myanmar. NPGPGL has been developing stopes up to 150 m from the surface at Shwesin vein system, and the mining activities are going to continue to deeper levels to fulfill the ore mineral supply. Creating a new stope opening under overlaying mined-out regions is not easy considering the instability of mined-out regions can affect the stope. The instability of new stope opening is not only due to its own induced stress but also the strong influence by the mined-out regions situated on upper part of the stope. Therefore, the understandings of ground behaviors and failure mechanisms of new stope opening due to the influence of overlaying mined-out regions are paramount to be studied. This paper describes in detail the strength factor and failure zones under the overlaying mined-out regions with different mine conditions by using numerical simulations, 3D finite difference software (FLAC 3D).

The Grouping of the Strike-Slip Offset Data and Its Relation With the Seismicity Along Middle Segment of the Xiaojiang Active Fault

The data of the strike-slip offset along the Xiaojiang active fault can be obviously grouped.The groups of small orders of magnitude data within 100 m show clear linear characteristics of increments between 8 m and 12 m,which indicates that the segments of the Xiaojiang active fault is of characteristic seismicity and the distribution of the values of each group indicates that there are smaller earthquakes and creep between two large earthquakes along each segment of the Xiaojiang active fault.The interval between two characteristic large earthquakes can be calculated with the increments for two groups of slip data and the slip rate of the fault.Furthermore,the frequency of smaller earthquakes can also be estimated by comparing the distributions of the displacements of the large earthquakes with the distributions of the values of each group of data.The groups of large slip displacements show that there is close relationship between the records of the displacements of the fault and the changes of the