基于时空聚类的引雷塔区域雷电地闪活动分析

近年来,基于主动防雷思想,利用引雷塔降低邻近输电线路遭受雷击概率的措施在实际中开展应用,但目前仍缺乏引雷塔对区域雷电活动影响规律的研究,对引雷塔的主动防雷效果及原理的研究仍存在空白。由于雷电地闪活动在时间和空间上具有丛聚性的特征,为了研究引雷塔区域雷电活动规律,基于雷电定位系统统计的佛山高明地区2011—2017年雷电活动数据采用网格法划定引雷塔区域。对区域内海量雷电数据进行时间和空间上的聚类处理,采用基于密度的聚类分析算法提取了雷暴时区内雷电地闪活动的轨迹,对雷电地闪活动过程中的分裂、聚合现象进行数据处理,并对比分析了引雷塔投产前后雷电地闪活动强度、雷电地闪运动轨迹以及雷电地闪走廊的趋向。结果表明,引雷塔对雷电活动有一定的吸引作用,雷电击中引雷塔区域并放电的概率大大增加,同时引雷塔对雷云电荷的消纳作用会使经过引雷塔区域后的雷电流幅值有一定程度的降低。引雷塔的建设在一定程度上改变了雷电走廊通道的主要方向和占比情况,所得结论可为未来引雷塔工程选址提供参考。

云南输电线路邻近典型地形区域的雷电地闪活动聚类分析

不同地区由于不同的气候条件、地形地貌等因素的影响,落雷分布存在很大的差异,对复杂地形情况下的落雷分布规律进行研究具有重要的工程实用价值。开展了输电线路区域的局部地形划分,采用基于DBSCAN算法与OPTICS算法相结合的改进聚类分析方法并得到不同地形下单次雷电地闪活动在时间属性和空间属性上的分布。根据结果发现,不同地形对雷电地闪活动的时空分布略有差异,其中,沿峡谷风道地形和山脊地形走向的雷电地闪活动轨迹占比较多,沿山谷地形和河流地形走向的雷电活动轨迹占比次之。同时对单次雷电活动经过不同地形前后的落雷频次和雷电流幅值进行分析,进一步分析地形对雷电地闪活动的影响规律。研究输电线路邻近区域宏观地形和局部地形地面落雷分布规律,能够为今后的差异化防雷工作提供工程借鉴和理论参考。

四川宜宾泸州长江河谷地带雷电监测数据特征分析

利用四川宜宾泸州长江河谷地带2011—2015年地闪数据,对该境内的雷电强度分布、频率分布、时间分布等特征进行了统计分析,为防雷技术服务提供科学合理的数据,为社会提供防雷减灾服务。

广东近年“龙舟水”期间地闪特征及其与降水关系

选取广东2018-2022年“龙舟水”期间(5月21日—6月20日)发生在粤港澳地区地闪定位数据,分析其地闪发生的特征,并结合86个国家站逐日降水资料探讨了地闪强度、频次与降水的关系。结果显示:(1)广东近5a地闪强度集中在-40~15kA;正闪发生占比38.80%,平均电流为6.28 kA;负闪发生占比61.20%,平均电流强度为-16.18kA;(2)逐日闪电频次较多,主要集中在5月下旬至6月上旬;降水量与总地闪频次随年份起伏变化基本一致,二者呈弱相关,相关性系数为0.45;另外,近年“龙舟水”期间总地闪频次逐时变化呈单峰型,而2021年总地闪频次逐时变化呈双峰型,2022年总地闪频次逐时变化呈三峰型。(3)广东中心地区发生地闪密度大,其平均地闪强度相对较小,而四周边缘地区地闪密度小,平均强度反而大;另外,粤东、粤北等丘陵地区“龙舟水”期间地闪强度普遍在20~25kA;而雷州半岛地区平均地闪强度大于25kA,尤其是2022年平均地闪强度达到了40kA。

Zircon U-Pb geochronology and geochemistry of diorite dikes from Nancha ore deposit in Tonghua area of Jilin and its geological significance

The authors presented geochronology and geochemical data of diorites from Nancha gold deposit in Tonghua region, with the aim to constraining its formation age, magma source and tectonic setting. LA-ICP-MS U-Pb dating results of zircons from the diorites indicate that the rocks were formed in the Middle Jurassic （171 ±2 Ma, MSWD = 1. 19）. Geochemically, these rocks have Si02 concentrations of 52. 52%-54. 90%,K20 of 2. 14%-3.84% , Na20 of 3. 17%-3. 35% , MgO of 7. 43%-9. 34% and high Mg# of 68. 57-72. 57. These rocks are characterized by enrichment in large ion lithophile elements（ LILE,such as K, Ba, Rb and Sr） and light rare earth elements （ LREE） , relatively depletion in high field strength elements （ HFSE, such as Ta, Nb, Ti and Zr） , and heavy rare earth elements （HREE）. These characteristics suggest that primary magma of the rocks were derived from the partial melting of mantle with miner crustal contamination, which may related to partial melting of mantle wedge by addition of sediment melt from subducting oceanic crust. Based on former and present studies, the authors consider that the Nancha ore deposit high-Mg diorites were formed in compres- sional structural setting which is similar to volcanic arc. It could be related to the subduction of the Paleo-Paci- fic plate beneath the Eurasian continent.

Zircon U-Pb geochronology and geochemistry of Early Cretaceous granodiorite porphyries in Hutouya,western Shandong and their implications for petrogenesis

Zircon LA-ICP-MS U-Pb age and whole-rock geochemistry data are presented for the Hutouya grano-diorite porphyries in Mengyin, western Shandong, to restrict its petrogenesis. The analyzed zircons exhibit os-cillatory growth zoning and core-rim textures in the cathodoluminescence images and have high Th/U ratios （0.04-1.66）,indicating its magmatic origin. The youngest group of magmatic zircon yields weighted mean 206Pb/238U age of 132 ±2 Ma, which represents the forming age of the granodiorite porphyries, i. e., the Early Cretaceous. The oldest group of magmatic zircon 207Pb/206Pb ages ranges from 2 398 Ma to 2 370 Ma, yielding a weighted mean age of 2 389 ±23 Ma,suggesting that the basement of the North China Craton should exist in the research area. Geochemically, the samples are characterized by high Si02（70. 38% and 64. 87% ） , low MgO （0.60% and 1. 53% ） and Mg# values （42. 92 and 50. 42）. Moreover, they show enrichment of light rare earth elements and large ion lithophile elements （e. g. Rb, Ba and K） , depletion of heavy rare earth ele-ments and high field strength elements （e. g. Nb and Ta） , positive anomaly of Pb, and negative anomaly of Ti. These results, together with previously published data, indicate that the Hutouya granodiorite porphyries were derived from partial melting of a delaminated lower continental crust and subsequent interaction with the mantle peridotites. They are consistent with the period of lithospheric thinning beneath the eastern North China Craton and may be formed in an extensional tectonic environment.

Geochronology,geochemistry and Hf isotopic study of Early Carboniferous granodiorites in Taerqi region,central Daxing'anling and its tectonic implication

Zircon U-Pb age,whole rock geochemical and zircon Hf isotopic data are presented for Late Paleozoic granodiorites from the Taerqi region,central Daxing'anling to constrain its petrogenesis and tectonic implication.LA-ICP-MS zircon U-Pb age data indicates that the Late Paleozoic granodiorites were emplaced with age of333.4 ± 2.2 Ma(Early Carboniferous).Geochemically,the granodiorite samples have Si O2= 60.54%-71.40%,Na2 O = 4.04%--4.66%,K2 O = 1.65%--4.27% and Mg O = 0.96%--3.53%,belonging to medium-K to high-K calc-alkaline I-type granites.They are slightly enriched in large ion lithophile elements(e.g.Rb,Th,U and K) and light rare earth elements,and depleted in high field strength elements(e.g.Nb,Ta and Ti),with εHf(t) values of 8.0--11.8 and Hf two-stage model ages of 586-829 Ma.All these geochemical features suggest that the primary magma was derived from partial melting of Neoproterozoic to Phanerozoic newly accreted lower crust.According to the geochemical data and regional geological investigations,the Early Carboniferous granodiorites formed in an island arc setting linked to the subduction of the Paleo-Asian Oceanic Plate beneath the Xing'an Terrane.This also implies that the Xing'an and Songliao terranes have not amalgamated before the Early Carboniferous.