A ca. 2.2Ga Acidic Magmatic Event at the Northern Margin of the Yangtze Craton: Evidence from U-Pb Dating and Hf Isotope Analysis of Zircons from the Kongling Complex

Objective The Yangtze craton collisional orogeny at ca. extensional events at ca. 1 experienced Paleoproterozoic 1.95-2.0 Ga and post-orogenic 85 Ga related to amalgamation of the Columbia （Nuna） supercontinent （Zhao and Cawood, 2012）. A ca. 2.15 Ga suprasubduction zone ophiolitic melange was recongized in the Archean- Paleoproterozoic Kongling Complex of the northern Yangtze craton （Han et al., 2017）. However, the tectonic evolution in early Paleoproterozoic from 2.4 Ga to 2.2 Ga remains unclear. We report here the presence of a suite of Paleoproterozoic （2.2 Ga） granites in the Huangling dome, northern Yangtze craton, which may provide important insights into crustal growth processes in the craton prior to the assembly of Columbia.

Krypton-85 dating of shallow aquifer in Hebei Plain

The inert gas radioactive isotope ^(85)Kr(with a half-life of 10.74 years), due to its stable physical and chemical properties, is an ideal tracer for shallow groundwater dating. In such a dating application, first the dissolved gas is extracted from groundwater in the field, then krypton is separated from the gas sample, and finally the isotopic abundance ^(85)Kr/Kr will be determined by an ATTA instrument. According to the atmospheric input curve of ^(85)Kr, the ^(85)Kr age of groundwater is determined. We conducted ^(85)Kr analysis in three wells in Zhengding County on the plains in front of the Taihang Mountains, and made a comparison with tritium(~3H) method.

In situ Rb-Sr dating of mica by LA-ICP-MS/MS

Mica exhibits a relatively high Rb/Sr ratio and possesses a closure temperature for the Rb-Sr isotope system that is higher than the ore-forming temperature range of low-to medium-temperature deposits.Consequently,utilizing the laser ablation(LA)technique for in situ Rb-Sr dating in mica constitutes a significant methodology for resolving the mineralization chronology of low-to medium-temperature hydrothermal ore deposits.In this study,we employed a combination of a triple quadrupole inductively coupled plasma mass spectrometer(ICP-MS/MS)and 193 nm LA system with SF_6as the reaction gas to achieve interference removal of~(87)Rb~+on~(87)Sr~+.We then developed an in situ Rb-Sr dating method for mica.In addition,an investigation was conducted to identify the factors that could influence the analytical accuracy of the method.Subsequently,we applied the developed method to carry out in situ Rb-Sr dating for the ZBH-25 biotite,a national primary reference material(GBW04439)for K-Ar dating,and yielded a younger age(ca.12%,relative standard deviation,RSD)than the reference K-Ar age when using NIST SRM 610 as the reference material for external calibration.This finding indicated that in the process of determining Rb-Sr ages for mica by LA-ICP-MS/MS,there are significant matrix effects between the NIST SRM 610 and the mica samples,resulting in inaccurate Rb-Sr ages.In response to this issue,a two-step calibration method is proposed here.Based on external calibration using NIST SRM 610,ZBH-25 biotite is employed as a second external reference material to perform a second calibration of the sample data to correct the matrix effect between the glass standards and the natural mica samples,thereby improving the accuracy of Rb-Sr dating by LA-ICP-MS/MS.Using the proposed method,in situ Rb-Sr dating by LA-ICP-MS/MS was performed on mica samples from monzonite exposed in Mt.Dromedary,New South Wales,Australia,porphyritic granodiorite in Fangshan pluton and albionite granite in the Gyirong area of Tibet.The obtained Rb-Sr age results show agreement with the recommended values within the analytical uncertainty,which serves to validate the accuracy and effectiveness of the proposed method.

Geological analysis and FT dating of the large-scale right-lateral strike-slip movement of the Red River fault zone

Tectonically, the large-scale right-lateral strike-slip movement along the Red River fault zone is char-acterized at its late phase with the southeastward extension and deformation of the Northwestern Yunnan normal fault depression on its northern segment, and the dextral shear displacement on its central-southern segment. Research of the relations between stratum deformation and fault movement on the typical fault segments, such as Jianchuan, southeast Midu, Yuanjiang River, Yuanyang, etc. since the Miocene Epoch shows that there are two times dextral faulting dominated by normal shearing occurring along the Red River fault zone since the Miocene Epoch. The fission track dating (abbrevi-ated to FT dating, the same below) is conducted on apatite samples collected from the above fault segments and relating to these movements. Based on the measured single grain’s age and the con-fined track length, we choose the Laslet annealing model to retrieve the thermal history of the samples, and the results show that the fault zone experienced two times obvious shear displacement, one in 5.5 ± 1.5 MaBP and the other in 2.1± 0.8 MaBP. The central-southern segment sees two intensive uplifts of mountain mass in the Yuanjiang River-Yuanyang region at 3.6―3.8 MaBP and 1.6―2.3 MaBP, which correspond to the above-mentioned two dextral normal displacement events since the late Miocene Epoch.

A Thermal Event in the Ordos Basin:Insights from Illite ^40Ar-^39Ar Dating with Regression Analysis

Four samples from a Permian reservoir in the Ordos Basin of North China were separated into twelve fractions in grain sizes of 〈0.5, 0.5-1 and 1-2 μm. Using the ^40Ar-^39Ar step-heating method, all of the fractions essentially yielded plateau ages ranging from 172.5 to 217.1 Ma. These scattered plateau ages might not have been obtained from pure diagenetic illites but from mixed clay minerals, although the samples were disaggregated using a gentle freeze-thaw cycle to free them of non-clay minerals. A regional thermal event, as suggested by several proxies, led to intensive iHitization as a distinct diagenetic process when the Yanshanian Movement triggered magmatism around the entire North China Block during the Jurassic to Cretaceous. Thermal illites formed during a short time period, whereas detrital illites came from various sources. The scattered plateau ages could have resulted from mixed degassing of thermal and detrital illites. Within one sample, the plateau ages decrease with the diminution of grain sizes, but it is difficult to extrapolate to the detrital-illite-free ages. Because the plateau age is a mixture of ages for thermal and detrital illites, this regression analysis studies the dependence of the plateau ages on the synthetic values of contents and ages of detrital illites instead of on the grain sizes. Comparing the samples to one another, the plateau ages show the same trend among the different grain sizes. Weighted by the contents and ages of detrital illites, linear regression analysis revealed the relationship between the plateau ages and the relative weight proportions. Based on iterated calculations, a thermal event age and a set of weight proportions were derived. The regressed thermal event age is 163.3±1.6 Ma, which coincides with regional thermal activities and links to gas accumulation.

Combined apatite fission-track dating, chlorine and REE content analysis by LA-ICPMS

As one of the best established low temperature thermochronology techniques,apatite fission-track(AFT)analysis has proved an important tool for constraining a wide variety of upper crustal processes,e.g.,landscape evolution,hydrocarbon exploration and tectonics[1].The most common method employed for AFT analysis is the external detector method(EDM)[1]and this involves the thermal neutron irradiation of samples for determination of

Activation of northern margin of the North China Craton in Late Paleozoic:Evidence from U-Pb dating and Hf isotopes of detrital zircons from the Upper Carboniferous Taiyuan Formation in the Ningwu-Jingle basin

LA-MC-ICPMS U-Pb dating has been performed on detrital zircons from the Upper Carboniferous Tai-yuan Formation (N-8) in the Ningwu-Jingle Basin, west of the North China Craton (NCC). The ages of 72 detrital zircon grains are divided into three groups: 303―320 Ma (6 grains), 1631―2194 Ma (37 grains, peaked at 1850 Ma), 2318―2646 Ma (29 grains, peaked at 2500 Ma). Detrital zircons of Group 2 and Group 3 were likely derived from the basement of the NCC. Group 1 zircons exhibit 176Hf/177Hf ratios ranging from 0.281725 to 0.282239, with corresponding negative εHf(t) values of -12.4―-30.3 and old Hf model ages of 1.4―2.2 Ga. These characteristics show a strong resemblance to those of Carboniferous igneous zircons from the Inner Mongolia Paleo-uplift (IMPU) on the northern margin of the NCC, but differ significantly from those of the Xing-Meng Orogenic Belt, suggesting that the source of the Tai-yuan Formation partly came from the IMPU. All detrital zircons of Group 1 have relatively high Th/U ratios (> 0.67), indicating a magmatic origin. The mean age (304 ± 6 Ma) of the two youngest grains is close to the depositional age of the Taiyuan Formation, suggesting a strong tectonic uplift and magmatism in the IMPU during the Late Carboniferous. This paper provides important geological evidence for the activation of the northern margin of the NCC in the Late Paleozoic.

Comparative Analysis of Climatic Change Trend and Change-Point Analysis for Long-Term Daily Rainfall Annual Maximum Time Series Data in Four Gauging Stations in Niger Delta

The aim of this study is to establish the prevailing conditions of changing climatic trends and change point dates in four selected meteorological stations of Uyo, Benin, Port Harcourt, and Warri in the Niger Delta region of Nigeria. Using daily or 24-hourly annual maximum series (AMS) data with the Indian Meteorological Department (IMD) and the modified Chowdury Indian Meteorological Department (MCIMD) models were adopted to downscale the time series data. Mann-Kendall (MK) trend and Sen’s Slope Estimator (SSE) test showed a statistically significant trend for Uyo and Benin, while Port Harcourt and Warri showed mild trends. The Sen’s Slope magnitude and variation rate were 21.6, 10.8, 6.00 and 4.4 mm/decade, respectively. The trend change-point analysis showed the initial rainfall change-point dates as 2002, 2005, 1988, and 2000 for Uyo, Benin, Port Harcourt, and Warri, respectively. These prove positive changing climatic conditions for rainfall in the study area. Erosion and flood control facilities analysis and design in the Niger Delta will require the application of Non-stationary IDF modelling.

兴县碧村遗址小玉梁台地F5建筑遗存研究

碧村遗址地处蔚汾河与黄河交汇处,是一处具有内外双重城垣的石城聚落。本文对碧村遗址小玉梁台地F5 (1)出土的6块木炭进行了树种鉴定、树轮年代学和碳十四年代加速器质谱测定。树种鉴定表明F5的建筑木材为松属双维管束亚属硬木松(Subgen. Diploxylon);利用木炭横切面年轮曲率和photoshop软件判断建筑木材年龄不小于119年,直径不小于27.06厘米;利用树轮年代学方法建立了跨度为68年的硬木松浮动树木年轮年表;对木炭系列样品进行碳十四年代质谱测定,最后一个年轮的年代约为公元前2027年(95.4%),F5建筑营建或修葺年代约为公元前2027年。该研究为小玉梁台地F5建筑构建或修葺提供了基础性资料。

Deformation characteristics of granitic rocks in Erguna ductile shear zone,NE China

The Erguna ductile shear zone is situated in the Erguna Massif,which has been exposed along the eastern bank of the Erguna River in northeastern China.The authors present comprehensive study results on the macro-and micro-structures,finite strain and kinematic vorticity,quartz electron backscatter diffraction(EBSD)fabrics,and geochronology of granitic rocks in the Erguna ductile shear zone.The deformed granitic rocks have experienced significant SE-trending dextral strike-slip shearing.Finite strain and kinematic vorticity in all deformed granitic rocks indicate that the deformation is characterized by simple sheardominated general shearing with S-L tectonites.Mineral deformation behaviors and quartz C-axis textures demonstrate that the deformed granitic rocks developed under greenschist to amphibolite facies conditions at deformation temperatures ranging from 450 to 550℃.New LA-ICP-MS zircon U-Pb ages indicate that these granitic rocks were formed in Early Triassic(~248.6 Ma)and Early Cretaceous(~136.7 Ma).All the evidence indicates that this deformation may have occurred in Early Cretaceous and was related to the compression resulting from the final closure of the Mongol-Okhotsk Ocean.

谷子抽穗期基因SiGI的表达与单倍型变异分析

谷子抽穗期是决定品种适应性的关键性状,解析抽穗期关键基因的表达规律及其单倍型变异特点可为提升品种改良效率奠定基础。本研究通过全基因组关联分析,发现了一个与抽穗期紧密相关的关联信号,该信号定位于谷子5号染色体的11062649 bp处,该位点附近存在一个拟南芥抽穗期基因AtGI的同源基因SiGI。使用qRT-PCR技术研究短日照(10 h光照/14 h黑暗)条件下SiGI 24 h节律变化规律,并对其进行了组织时空表达及亚细胞定位分析。利用697份谷子品种,分析SiGI编码区和启动子区的遗传多态性和单倍型变异规律,并对单倍型的表型效应进行鉴定。结果显示,SiGI在光周期响应组织(根、茎、叶等)中高表达,亚细胞定位于细胞核,在傍晚表达量上调,呈现出24 h节律性表达模式。SiGI在不同谷子品种中存在丰富的多态性,其中,启动子Hap-6单倍型较Hap-3单倍型品种的相对表达量显著上调了约1.5倍(P=0.0083)。在8个不同种植环境下,Hap-6单倍型品种的抽穗期显著提前,并在4个环境中株高显著降低。结果表明SiGI基因的Hap-6单倍型具有早熟且对产量影响较小的优势,可作为优异单倍型用于分子育种选择。

东昆仑东段各玛龙闪长岩年代学、地球化学特征及成因分析

各玛龙地区位于东昆仑造山带东段南部,该地区构造活动与岩浆活动强烈。本文以两件花岗闪长岩和两件英云闪长岩为研究对象,开展LA-ICP-MS锆石U-Pb年代学和岩石全岩元素组成研究,探讨岩石成因类型和岩浆源区特征,分析闪长岩的构造演化环境。研究结果表明:两件具有代表性的闪长岩样品成岩年龄分别为405.3±1.1 Ma和405.8±1.2 Ma,说明成岩时代为早泥盆世;4件闪长岩样品具有高硅、高铝、高碱、贫钙、贫镁、弱过铝质特征,属于弱过铝质高钾钙碱性系列岩石;4件样品中未发育S型花岗岩的代表性矿物,并且Rb/Sr值为0.32~0.43,均小于0.9,A/CNK值为0.98~1.09,均小于1.1,符合I型花岗岩的地球化学特征;通过分析La-La/Sm图解与(Zr+Nb+Ce+Y)-(Na_(2)O+K_(2)O)/CaO图解,同时结合Nb/Ta、Zr/Hf、Nb/U、Rb/Sr、Ti/Y、Ti/Zr值,可以得知各玛龙地区闪长岩是由地壳岩石部分熔融形成的,并且可能伴有幔源物质的参与。结合前人研究及(Y+Nb)-Rb图解与Rb/30-Hf-Ta*3图解可知,各玛龙地区闪长岩形成于早泥盆世东昆仑造山带的后碰撞伸展环境。

印度-欧亚板块碰撞带中下地壳分层流动与减薄:来自希夏邦马峰地区藏南拆离系构造解析的证据

造山带中下地壳物质流动是造山带地壳变形的重要表现,它制约着造山作用过程。印度-欧亚板块碰撞带内藏南拆离系为理解陆-陆板块会聚过程中中下地壳物质流动提供了范例。本项研究围绕喜马拉雅造山带中段希夏邦马峰地区藏南拆离系开展构造解析、显微构造观察和淡色花岗岩独居石U-Th-Pb年代学分析。结果表明希夏邦马峰地区藏南拆离系为一宽约2km的韧性剪切带,剪切变形岩石具有显著的分层流动特征。藏南拆离系新生代时期经历了两阶段塑性变形:D 1期变形表现为面理S 1、对称状透镜体和层间褶皱F 1的发育;D 2期变形表现为糜棱面理S 2、近E-W向拉伸线理L 2、不对称旋转碎斑和透镜体及褶皱的发育。运动学标志表明D 2期变形为上盘向东的运动学特征。淡色花岗岩独居石U-Th-Pb测年分析获得三组年龄:32.26±0.29Ma、22.31±0.18Ma和15.54±0.11Ma,这三组年龄的淡色花岗岩分别表现出D 1期变形、D 2期变形和未变形特征。结合前人已发表数据,本文得出藏南拆离系ca.35~26Ma发生以纯剪为主的剪切变形(D 1期),ca.26~15Ma发生以单剪为主的剪切变形(D 2期)。D 1-D 2期变形为一递进剪切变形,二者可能归咎于印度-欧亚板块碰撞过程中中下地壳固态分层流动。

基于主成分分析的果蝇算法优化支持向量机回归的红枣产量预测

随着大数据技术和人工智能的快速发展,针对当前红枣产量预测模型精度低、模型优化时间过长等问题,以山西省1993—2020年的红枣产量及17个维度的因素作为基础数据,提出一种基于主成分分析的果蝇算法优化支持向量机回归(principal component analysis-fruit fly optimization algorithm-support vector regression,PCA-FOA-SVR)的红枣产量预测模型。首先利用主成分分析(principal component analysis,PCA)对数据进行降维处理,以5维的指标作为输入变量,产量作为输出变量;其次以支持向量机回归(support vector regression,SVR)为基础模型,利用果蝇优化算法(fruit fly optimization algorithm,FOA)对SVR参数惩罚因子c和核函数参数g进行寻优,构建PCA-FOA-SVR模型。对试验结果进行验证。发现PCA-FOA-SVR的均方根误差(root mean square error,RMSE)、平均绝对误差(mean absolute error,MAE)、决定系数R 2分别为3.11、3.01、0.96,SVR的各指标分别为5.33、4.07、0.9,分别提高了41.7%、26%、6.7%,最后通过GM(1,1)对各维度的数据进行预测,利用PCA-FOA-SVR模型对未来10年山西省红枣产量进行预测,结果显示在2025年红枣产量会达到一个峰值,对后续相关研究提供了一定的科学依据。

温州朔门古港宋代文化层沉积间断及其成因探讨

温州朔门古港遗址于2022年被评为年度全国十大考古发现,为研究1700年以来瓯江下游地区的历史环境变迁和人地关系提供了新的素材。本研究对遗址区内从标高2.5m到-4.5m的3个剖面及1个钻孔进行了分析,依据沉积物粒度和考古文化层的分布,整个遗址区地层自下至上可以分为4层,其中在第二层砂泥互层现象明显,与上下沉积环境差异显著,为较明显的洪水事件层。综合沉积物的AMS14C测年结果、文化层遗存发现和历史文献记载,发现本次洪水事件层与两宋期间温州朔门古港遭受的一期极端洪水灾害事件密切相关。本研究通过结合地层学分析、文物鉴定和历史文献验证的方式,重建了温州古港在两宋交际之时发生的环境变化及古人类响应过程,即:正常贸易活动-极端灾害侵扰-环境逐渐稳定-恢复贸易进程的四个阶段演化。

播期对不同穗型冬小麦生长及产量的影响

为提高冬小麦产量,开展播期对不同穗型冬小麦生长及产量影响的研究。本研究以大穗型品种‘泰农18’、中穗型品种‘山农18’和多穗型品种‘红地95’为试验材料,设置9月30日、10月10日、10月20日、10月30日4个播期,对不同播期条件下的株高、叶面积指数、茎蘖数、产量及产量三要素进行测定。结果表明,随着播期推迟,‘泰农18’、‘山农18’、‘红地95’的株高呈下降趋势,叶面积指数、单位面积茎蘖数、穗数、穗粒数、千粒重和产量均呈现先上升后下降的趋势。产量在播期为10月10日时最高,分别为9.38 t/hm^(2)、8.94 t/hm^(2)、9.22 t/hm^(2),播期为10月30日时最低,分别为7.26 t/hm^(2)、7.32 t/hm^(2)、7.74 t/hm^(2),比最高处理分别下降22.6%、18.1%、16.1%。通过对3个品种产量和三要素之间的通径分析可知,播期主要影响大穗型品种‘泰农18’的穗粒数,中穗型品种‘山农18’的千粒重,多穗型品种‘红地95’的单位面积穗数。综合比较,3个品种的最适播期均为10月10日,晚播可造成株高、叶面积指数、茎蘖数下降,产量降低。

四川盆地西北部中侏罗统沙溪庙组物源:碎屑锆石U-Pb年代学的证据

通过对沙溪庙组三个砂岩样品进行碎屑锆石U-Pb定年,结果显示,其年龄区间呈现为五个年龄组,分别为2660~2300 Ma,1905~1738 Ma,1690~1442 Ma,866~811 Ma和298~160 Ma。通过与周边区域不同地块(体)锆石年龄对比并综合区域相关地质资料,发现2660~2300 Ma和1905~1738 Ma两个年龄组的碎屑锆石主要来自南秦岭造山带与扬子板块北缘,少量来自碧口地体和松潘-甘孜地体;1690~1442 Ma,该年龄组碎屑锆石来源于武关岩群、武当岩群及碧口杂岩;866~811 Ma,该组碎屑锆石主要来源于扬子克拉通北缘、碧口岩群及南秦岭造山带;298~160 Ma,碎屑锆石主要来自南秦岭造山带和晚三叠世的松潘-甘孜地体。以上证据表明,沙溪庙组物源主要来自南秦岭造山带及松潘-甘孜褶皱带,扬子克拉通则贡献较少,且南秦岭已于沙溪庙组之前隆升结束,阻挡了来自北秦岭及华北板块南缘的物质输入。

青海沟里地区斜长角闪岩锆石U-Pb年代学、Lu-Hf同位素特征及其指示意义

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