The preparation of 238U targets on 2mm Al foils

Preparation of 238U on 2μm Al foils by molecular plating technique is described. In order to obtain optimum conditions for deposition, several parameters influencing the quality of layers such as current density, distance between the anode and cathode and the deposition time were investigated. The target thickness was determined by spectrophotometry. The uniformity and morphology of the target surface were studied by means of scanning electron microscopy, energy dispersive X-ray spectrometry and Infrared spectra. The results show that uranium is deposited in its oxide or hydroxide form uniformly and adherently onto the foil.

洞穴碳酸盐^230Th-^234U-^238U测年初始钍校正的等时线研究

IEECAS SKLLQG

铀矿坑水样中铀电沉积层的表征

描述了硫酸铵溶液中铀矿坑水样品中铀的电沉积层特性。电沉积液为10ml0.8M的硫酸铵溶液,电流密度0.6A/cm2,pH值为2.5,电镀1h。电沉积经化学分离后的水样品和电沉积的纯硝酸铀酰样品进行了比较,并对二者分别做了红外(IR)光谱、扫描电镜(SEM)、元素分析以及α能谱测量。IR谱上铀酰离子的反对称伸缩振动峰在887cm-1附近,使电沉积在不锈钢片上的铀主要以铀酰离子水合物的形式存在,有一部分NH4+以NH3的形式替代水合物中的水,使电沉积层中铀的化合物形式为UO2(OH)2.xNH3.yH2O或者UO2(OH)2-x.(ONH4)x.yH2O,铀酰离子通过链的形式形成聚合结构。SEM照片显示电沉积层均匀,没堆积成团现象出现。α谱表明电沉积层中铀的同位素主要是238U和234U,相应的α能量峰4198和4773keV很显著,没其它峰的干扰。

~(239)Pa的鉴别及其特性

利用60 MeV/u18O离子束轰击天然铀靶,经多核子转移反应生成重丰中子核素239Pa。用放射化学方法从被照射的靶中分离出镤。借助于239Pa和它的子体239U的γ射线观测和分析,鉴别了239Pa,测得239Pa的半衰期为(106±30)min。长寿命同位素,如232Th和238U,可给出一个测定核合成持续时间的可能性,而中等寿命同位素,如235U,则可给出有关产生函数时间历史的信息。总地说来,通过232Th/238U2、35U/238U或244Pu/238U的比率,用公式NA(Δ)/NB(Δ)=(PA/PB)f(λA,λB,S0,λR,Δ)便可推导出宇宙年龄。由239Pa的衰变途径,可简单叙述239Pa的异常长的半衰期对于宇宙年龄估计的影响。

基于双核模型对准裂变产物质量分布的研究

在双核模型基础上引入一维的Kramers公式,计算了48Ca+244Pu,48Ca+238U和58Fe+232Th这三个反应准裂变碎片的质量分布,得到了与实验比较符合的结果.同时提取出了碎片质量分布随时间的演化关系,为理解熔合与准裂变竞争过程提供了非常有用的信息.由于准裂变在重离子熔合反应中起着重要作用,理论计算与实验结果的比较是对现有熔合模型的重要检验.

~(40)Ar+~(238)U实验介绍

主要介绍了利用兰州重离子加速器提供的270 MeV的40Ar离子束轰击238U靶,通过熔合蒸发反应进行试合成Z=110附近的新同位素的实验情况。分析了目前关于超重核研究的现状并描述了这次实验的目的、可行性分析、实验装置以及实验过程等。本次实验仍然用氦喷嘴技术对产物进行传输,并用一套具有数对探测器组的转轮收集探测系统对产物进行收集和测量。

单次分子镀法制备部分La系及~(238)U靶的实验研究

采用单次分子镀方法研究了异丙醇-硝酸体系中电流密度、分子镀持续时间及两极间距离对镀层性能和电沉积效率的影响,确定了制备La,Sm,Eu,Gd,Tb靶及238U靶的最佳工艺条件。因制备的靶不同,电流密度一般介于2—8mA/cm2之间,两极间最优距离为3cm,分子镀1h,用分光光度法测定各靶的沉积效率均高于85%。利用扫描电子显微镜(SEM)对部分靶的表面形貌分析后发现靶面结构均匀致密。目前制得的Gd靶和Tb靶已用于中国科学院近代物理研究所加速器SFC低能核化学终端上,利用19F束流轰击,分别产生了Ta和W的短寿命同位素,从而成功完成了Db(Z=105)及Sg(Z=106)的模型试验。

环境样品的低水平放射性测量

环境样品中的低水平放射性测量在环境放射性现状调查和探矿中有广泛的应用。本论文对CSR环境水样品的放射性利用γ能谱方法进行了测量；对铀矿坑水样铀电沉积层用红外谱图和扫描电镜进行了表征，并且对其进行了α能谱测量；对便携式钾40探测器样机在不同条件下进行了测试。 CSR环境水样品经过采集，静置，预处理和封装，用高纯锗探测器在低本底大铅室内对水样品进行了测量，每个样品测量86400秒。标准源由中国原子能科学研究院提供，用相对比较的方法，给出样品中天然铀、钍、镭和钾的放射性活度。测量结果表明，CSR环境水样品中的放射性处于兰州地区本底水平，在样品中没有发现人工放射性核素。 对铀矿坑水样中的铀进行离子交换化学分离，在0.8M的硫酸铵溶液中进行电沉积，电流密度为0.6A cm-2,pH值为2.5；和同样条件下电沉积的硝酸铀酰进行对比，并对二者分别作了红外光谱、扫描电镜、元素分析以及α能谱测量，红外谱上铀酰离子的反对称伸缩振动峰在887cm-1附近，电沉积在不锈钢片上的铀主要以铀酰离子水合物的形式存在，电沉积层中铀化合物形式为UO2(OH)2•xNH3•yH2O或者UO2(OH)2-x•(ONH4)x•yH2O。扫描电镜照片显示电沉积层均匀，没有成团现象出现。α谱表明电沉积层中铀的同位素主要是238U和234U，相应的α能量峰分别为4198keV和4773keV。 对研制的40K探测器样机在屏蔽和未加屏蔽的条件下进行了测试，测量配制的40K标准源，绘出标准曲线，在同样的条件下测量未知钾含量的样品，根据峰面积计算40K的含量。研制的40K探测器样机基本满足样品中钾含量测量的需要，在野外测量时，在一定程度上受本底的影响

青岛市区辐射环境质量评价

安全环境是人类赖以生存的基础，天然放射性辐射环境是人类生存环境的重要组成部分，放射性物质存在于各类物质中，包括空气、水源和土壤等。放射性物质的辐射对环境的影响往往被人们所忽视，但又是最危险的环境影响因素。为了生存和健康不仅需要了解重金属和有机物污染，而且需要了解辐射污染。 天然放射性辐射环境与该区域内的地质环境密切相关。青岛地区燕山期岩浆活动频繁，形成了以钾长花岗岩和二长花岗岩为主的大规模侵入岩体，大多数母岩为富含铀、钍的花岗岩。本论文选择青岛地区做为放射性的研究区，该花岗岩地区与放射性核素的辐射强度的关系具有典型的代表性。 论文在大量密集测量地表岩石、土壤γ总量、土壤中238U、232Th 、40K放射性核素的含量基础上，分析了天然放射性辐射环境与该区域内的地质环境. 分析了环境中氡的来源及迁移机制，给出了氡的运移理论模型，指出了环境中氡的危害及其土壤中的分布与地质环境的关系。分别从内照射和外照射的角度，将土壤中238U (226Ra) 、232Th 、40K放射性核素的比活度、γ能量谱、环境中的氡浓度和直接测量空气中的吸收剂量率相结合，首次对青岛地区的辐射环境进行了研究和评价，可为奥运和青岛市长远发展提供科学保障。 结果表明研究区内土壤中的238U含量低于全国及世界平均值，土壤中232Th含量分别是全国和世界均值含量的1.1和1.5倍, 土壤中40K含量分别是全国和世界均值含量的2.43和2.44倍，因此空气中的吸收剂量率高于全国（81.5nGy•h-1）和世界（80 nGy•h-1）约1.2倍。通过能谱估算的空气吸收剂量率与实际测量值近似相等。研究区的年有效剂量为0.83 mSv，低于世界平均年有效外部照射的剂量限值1.0mSv，外照射指数和内照射指数均小于1，该区的等效镭浓度Raeq均值为197 Bq•kg-1，低于建议最大容许值370 Bq•kg-1，基于以上的各类指标均在世界均值或容许值范围内，可以认为该区的外照射水平属于安全辐射范畴。 222Rn浓度对人体内部照射具有举足轻重的地位，也是评价辐射环境质量的关键所在。本文采用经典的氡在空气中的扩散和对流的理论模式，通过研究区内的土壤中铀的含量推算出离地面1米高的空气中的氡的浓度，并且分析了土壤中的氡浓度与土壤中的放射性核素U、Th、K的含量的关系。研究区的土壤氡浓度总体平均值为5887Bq/m3，与全球土壤氡浓度的平均值7400 Bq/m3相比属于土壤氡浓度正常地区。由于青岛市区土壤覆盖层很薄,地表储气条件较差，造成土壤氡逸散。因此除区内土壤氡浓度几处偏高区以的其他区域，甚至断裂带上他和其他区域的土壤氡浓度也普遍偏低。通过计算可以得出青岛市区大气中氡浓度所导致的居民室外吸入氡子体所产生的年均人有效剂量估算结果是0.94mSv/a。这与联合国辐射防护委员会公布世界平均本底值1.2mSv/a相比,此值在正常范围内。 这个地区虽然大面积出露富含放射性物质的花岗岩，由花岗岩风化形成的土壤中放射性核素含量（钍、钾）也较高，但是因为铀含量不高，另外本区临海，一年四季的风速较大，因此本地区室外和室内空气中氡浓度不高。 综上可以得出结论：本区的辐射环境属于安全区域，适于人类生活。 本论文研究成果和创新点有：首次在大量密集测量的基础上，系统地对青岛地区的辐射环境进行了研究和评价；在数据采集方面，采用直接就地测量，跟其他调查方法比，采样密度大，数据量大。从研究方法方面，本文从外照射和内照射的角度，采用了多指标相结合的综合方式来评价本区的辐射环境质量，详实可信；引入GIS技术，和放射性评价相结合，较为系统深入地探讨了放射性核素和氡浓度的分布特征及其与岩性的关系。

西天山造山带古生代构造演化与地壳增生—来自花岗岩和蛇绿岩的证据

The Central Asian Orogen Belt (CAOB), which is different from the subductional orogen and the collisional orogen, is known as the most important site of crustal growth in the Phanerozoic, and it has been a ‘hot spot’ for studying the orogenic belts. The Chinese West Tianshan Orogen is occupying the west-southern part of the CAOB and is of great importances to understand the orogenic processes and the continental growth in the Central Asia. The West Tianshan Orogen had undergone complex tectonic evolutional processes in Paleozoic times and large volumes granitic rocks have recorded important information about these processes. Litter is known about Phanerozoic continental growth in the Western Tianshan area so far, compared with the other areas of the CAOB, such as eastern Junggar, western Junggar, Altai and Alakol. The aim of this dissertation is to set up the chronology frame of granitoids in western Tianshan, provide new evidence for the tectonic evolution and discuss the Paleozoic continental growth in this area, on the basis of the studies on the isotopic chronology, major element, trace element and Nd-Sr isotopic geochemistry of granitoids and the isotopic chronology and geochemistry of the ophiolites in this area, especially the Kule Lake ophiolites. 25 precise SHRIMP U-Pb zircon and LA-ICPMS U-Pb zircon ages have been obtained in this dissertation. The granitic rocks in western Tianshan had been formed during two periods: the granitic gneiss with an age of 896Ma, possibly representing the forming age of the Precambrian basement; the granitic rocks with ages varying from 479Ma to 247Ma, recording the Paleozoic orogenic process of western Tianshan. The granitoids in western Tianshan are composed of intermediate-basic rocks, intermediate rocks, intermediate-acid rocks and acid rocks, mainly intermediate-acid rocks and acid rocks. They are mostly granite, granodiorite, quartz syenite and monzodiorite. Different types of granitic rocks are exposed in different tectonic units. The granitoids on the northern margin of the Yili Plate mainly formed in late Paleozoic (413Ma ~ 281Ma), those with ages varying from 413Ma to 297Ma show continental arc affinities and the magnesian calc-alkalic metaluminous diorite of 281Ma display the geochemical characteristics similar to those of granites formed during the post-orogenic period. The granitiods on the southern margin of the Yili Plate include the adakite diorite of 470Ma which was formd by partial melting of thickened lower crust, the post-collisional alkali-feldspar granite of 430Ma, the volcanic arc granite of 348Ma and the Triassic post-collisional granite. The granitoids in the Central Tianshan Plate formed in 479Ma ~ 247Ma, mainly in 433Ma ~ 321Ma. The granitic rocks with ages of 479Ma ~ 321Ma are magnesian calc-alkalic to alkalic rocks with continental arc affinities. A few post-collisional granitoids of 276Ma ~ 247Ma may have inherited the geochemical characteristics of pre-existing arc magma. The granitic rocks in Southern Tianshan (northern margin of the Tarim plate) formed two stages, 420Ma ~ 411Ma and ca. 285Ma. The magnesian calcic to alkalic granites of 420Ma ~ 411Ma may formed during the extension process of the continental margin. The granite of 285Ma includes mostly ferroan calc-alkalic to alkali-calcic rocks with high SiO2 and high alkaline contents, and obviously negative anomaly of Eu, Ba, Sr, P, Ti, similar to the geochemical characteristics of the A-type granite which is formed during post-collisional extension. The Kule Lake ophiolite in southern Tianshan shows the affinity of N-MORB. A SHRIMP zircon U-Pb age of 425±8Ma has obtained for gabbros. Some zircons have given another group of 206Pb/238U age 918Ma, which may indicate the information of the pre-exist old basement rock. The small oceanic basin represented by Kule Lake ophiolite probably developed on the split northern margin of Tarim block. A model for Paleozoic tectonic evolution of the West Tianshan Orogen has been proposed here on the basis of the new results obtained in this dissertation and the previous published data. In Early Cambrian, the Terskey Ocean occurred along the North Nalati fault (NNF), and it separated the Yili plate from the Central Tianshan plate which was probably connected with the Tarim plate. The Terskey Ocean probably subducted towards south under the Central Tianshan plate and towards north under the Yili plate simultaneously. In the early stage of Late Ordovician, the Terskey Ocean had been closed, and the Yili and Central Tianshan plates collided. Meanwhile, extension happened within the joint Central Tianshan and Tarim plates gradually and the Paleo-South Tianshan Ocean had been formed. In Early Silurian, the Paleo-South Tianshan Ocean began to subduct beneath the composite Yili-Central Tianshan plate, which was intruded by volcanic arc granitoids. In Middle Silurian, the Paleo-South Tianshan Ocean, which had reached a certain width, was subducting strongly. And this subduction may have produced voluminous granitoids in the Central Tianshan plate. In the latest stage of Carboniferous, the Paleo-South Tianshan ocean closed, and the Yili-Central Tianshan plate and Tarim plate collided. In Late Cambrian, Paleo-Junggar Ocean occurred to north of the Yili plate; and started to subduct towards south under the Yili plate in Ordovician. This subduction may have produced a magma arc on the northern margin of the Yili plate. In Late Carboniferous, the Paleo-Junggar Ocean had been closed. The Yili-Central and Junggar plates amalgamated together. The West Tianhan Orogen may undergo a post-collisional collapse since Permian. And the magmatic activities may continue to early Triassic. The initial 87Sr/86Sr ration of the granitic rocks in the western Tianshan Mountains varies from 0.703226 to 0.716343, and Nd（t）from -6.50 to 2.03. The characteristics of Sr-Nd isotope indicate that the source of granitic material is not a sole source, which may be produced by mantle-crust magma mixing. In Paleozoic time, lateral growth of the continental crust along active continental margins was dominant, whereas the vertical growth of continental crust resulted from post- collisional mantle derived magmas was not obvious.

东准噶尔和尔赛斑岩铜矿特征及其形成的构造背景

Hersai porphyry copper deposit(PCD) of eastern junggar, newly discovered copper deposit, is located at the eastern segment of the Xiemisitai-Kulankazigan-Zhifang-Qiongheba Paleozoic island arc, Eastern Junggar. The Hersai PCD is developed in a intrusive complex, characterized by intensive and multiform hydrothermal alteration, including potassic alteration, silification, chloritization，sericitization，kaolinitization and carbonatization. Granodiorite, grandiorite porphyry, granite and concealed explosion breccia are hosts of the ore bodies containing veinlet and disseminated ore. Ore-bearing granite (ZK107-1-9), granodiorite (ZK107-1-9) and Ore-barren granodiorite (HES2-1) are selected to date zircon U-Pb age by SHRIMP method, and have an age of 429.4±6.4Ma ,413.0±3.4Ma and 411.1±4.8Ma, respectively, showing that they were emplaced from Late Silurian to Early Devonian. In addition, sample ZK107-1-9 has some hydrothermal zircons with a weighted mean 206Pb/238U age of 404.9±3.7Ma which is interpreted to be related to the granodiorite porphyry. Re-Os dating of five molybdenite samples yielded a weighted average model age of 408.0±2.9Ma, indicating the metallogenic epoch of the Hersai PCD. The ore-forming age is close to the petrogenic time of garnodiorite (411-413Ma), this suggests the ore-forming porphyry is most possiblely granodiorite porphyry. Systematic major - trace elements and Rb-Sr-Sm-Nd-Pb-Hf isotopic characteristics were studied. Analysis results show that these intrusives have some interesting and special characteristics, as following:1) containing both calc-alkaline rocks and high potassium calc-alkaline rocks ; 2) have some characteristics of adakite, but not totally, such as much lower La/Yb ratios and no Eu anomaly or just faint Eu anomaly; 3) have an initial 87Sr/86Sr ratios(0.703852-0.704565) similar to that of BSE, positive εNd(t) values between 6.1 and 7.4, the initial 206Pb/204Pb values (17.576-17.912), 207Pb/204Pb values (15.400-15.453) , 208Pb/204Pb values (37.252-37.466) , and high εHf(t) values (10.2-15.4) close to the value of depleted mantle. These geochemical features suggest that these igneous rocks in the Hersai area not only have some characteristics of island arc, but also some characteristics that only appear in the continental margin arc. It is suggested that Hersai PCD is formed in the subduction setting by the partial melting of young crust. These works and advancements mentioned in the paper are helpful to understand the deposit geology, geochemistry and metallogenesis of Hersai PCD. It is also significant to understand mineralization and tectonic setting in the Qiongheba area.

东海和冲绳沉积物中自生铀蓄积过程及控制机理

采用同位素稀释ICP—MS测定法，对中国东海陆架及日本冲绳海槽的6个沉积物芯中U和Th的同位素地球化学行为进行了研究，以了解氧化还原敏感元素U在近海次氧化性沉积物中的蓄积行为，并评价其在全球海洋铀平衡中的意义。东海沉积物芯中，^238U浓度及^238U／^232Th比值随深度变化不明显。但是在冲绳海槽沉积物芯中，^238U浓度及^238U／^232Th比值在沉积芯表层氧化带显示较低值，然后在次氧化层随深度增加而增加。^230Th和^232Th浓度在所有沉积物芯中基本不随深度变化。这些结果说明，冲绳沉积物中有“自生铀”的蓄积过程发生，蓄积速率约为（47±5）-（90±8）ng／（cm^2·a），与文献报道的世界其他海域次氧化性沉积区大致相当。进一步证明了U在近海次氧化性沉积区的蓄积对于全球海洋铀平衡有重要意义。“自生铀”的主要蓄积机制是海水U（Ⅵ）向沉积物迁移，在还原条件下被还原为惰性的U（Ⅳ）并被吸附在沉积物固体相上。

都龙锡锌矿床锡石和锆石U-Pb年代学：滇东南白垩纪大规模花岗岩成岩-成矿事件

都龙锡锌矿床是我国最大的锡石硫化物矿床之一.由于缺少可靠的年代学数据,对该矿床的成因尚存在较大争议.本文报道了利用锡石和锆石U-Pb法,首次获得的都龙锡锌矿床及相关的燕山晚期老君山花岗岩的年龄.其中,锡石TIMS法^206Pb/^238U年龄加权平均值为79.8±3.2Ma（MSWD=3.16）,^238U/^204Pb-^206Pb/^204Pb等时线年龄为82.0±9.6Ma（MSWD=4.81）;隐伏花岗岩的锆石SHRIMP法^206Pb/^238U年龄加权平均值为92.9±1.9Ma（N=10,MSWD=0.71）,花岗斑岩的锆石SHRIMP法^206Pb/^238U年龄加权平均值为86.9±1.4Ma（N=9,MSWD=3.70）,表明锡（铜）矿化主要与晚白垩世岩浆热液活动有关.结合个旧、白牛厂两个超大型矿床和相关花岗岩体的年代学资料,指示滇东南地区于白垩纪存在以锡矿化为特色的大规模花岗岩成岩-成矿事件,可能与晚中生代以来华南地块岩石圈伸展有关.

碳酸盐岩风化过程中的U－Th不平衡研究－以黔中、黔北为例

为了进一步获得贵州碳酸盐岩风化成土过程的信息，为测定风化成土速率的研究工作奠定基础，本次研究工作通过U－Th的地球化学特征与主量元素、微量元素、稀土元素的地球化学特征的对比研究以及U－Th不平衡来研究贵州两个碳酸盐岩风化剖面的风化成土过程，并得出以下总体认识： 贵州碳酸盐岩风化剖面中的238U－234U－230Th不平衡说明风化剖面中的U－Th不平衡与风化过程密切相关，与风化壳中矿物和铁壳的演化特征密切相关。风化剖面不仅被简单的持续积累或者滤失过程所控制，而且被每一个土层中的复杂的重组过程所影响。U－Th不平衡也说明风化系统的扰动可能与中更新世晚期的气候变化有关。风化剖面中的U－Th不平衡是由母岩碳酸盐岩的风化、风化流体的溶解作用、表土层中的有机质、铁质结核带中的氧化铁矿物以及伊利石、高岭石等粘土矿物对U、Th的吸附作用、α反冲作用以及微生物的还原作用等共同作用的结果。 具体结论如下： （1）两个风化剖面中的U、Th都在半风化层中相对基岩强烈富集，安顺白云岩风化剖面中U、Th在全风化层中下部富集；而遵义石灰岩风化剖面中的U在全风化层中部富集，Th在全风化层上部富集，然后向表土层逐渐减少。 （2）U、Th在半风化层中相对基岩强烈富集，是因为在半风化层中，基岩中的原生矿物发生溶解、蚀变，生成新的次生粘土矿物伊利石，而伊利石对U、Th具有强烈的吸附能力。风化剖面中U、Th的富集主要与地表水的淋滤作用以及铁壳在进一步的风化过程中溶解释放出其中所富集的U、Th，而U、Th向下重新迁移的过程有关。 （3）风化剖面中U、Th的分布特征说明U、Th的含量与风化过程密切相关，与风化壳中的矿物和铁壳的演化特征密切相关。遵义石灰岩风化剖面中U、Th的淋失程度比安顺白云岩风化剖面中U、Th的淋失程度弱也说明了遵义石灰岩风化剖面的风化程度要低于安顺白云岩风化剖面的风化程度。 （4）安顺白云岩风化剖面中，234U/238U在<1和＞1之间交替变化。除在剖面中部，230Th/238U≈1外，230Th/238U基本上都＞1。 （5）安顺白云岩风化剖面中的238U －234U－230Th不平衡表明：安顺白云岩风化剖面中的U－Th不平衡是母岩碳酸盐岩的风化、风化流体的溶解作用、表土层中的有机质、铁质结核带中的氧化铁矿物以及伊利石、高岭石等粘土矿物对234U、230Th的吸附作用、α反冲作用以及微生物的还原作用等共同作用的结果。 （6）遵义石灰岩风化剖面中234U/238U除少数几个点外，大多数采样点的234U/238U都＜1。除了少数几个点外，大部分230Th/238U＞1。 （7）遵义石灰岩风化剖面中的238U －234U－230Th不平衡表明：234U－238U不平衡主要是由地表水和入渗水的溶解作用以及α反冲作用为主要的控制机制。而风化剖面中230Th－238U不平衡主要是由表土层中的有机质、高岭石、氧化铁矿物以及伊利石对230Th吸附作用和α反冲作用共同作用的结果。 （8）将U的迁移模型应用于本研究中的两个碳酸盐岩风化剖面，说明这两个风化剖面都被U的近期积累或者滤失过程所影响，风化系统处于过渡的不稳定状态，并通过U在风化剖面中的重新迁移将系统带回稳定状态。 （9）由等时线定年法计算出的安顺白云岩风化剖面的年龄范围为：87.0±7.8－479.2±47.9ka；遵义石灰岩风化剖面的年龄范围为：62.3±8.7－353.3±31.8ka。 （10）由等时线定年法可知：两个风化系统将在～1.1Ma达到稳定状态。 （11）碳酸盐岩风化剖面应用U的迁移模型得出的U的迁移过程与风化剖面中主量元素和微量元素的迁移特征相吻合，说明模型的选择是正确的。 （12）整个风化剖面的238U－234U－230Th不平衡说明风化剖面中的U－Th不平衡与风化过程密切相关，与风化壳中矿物和铁壳的演化特征密切相关。风化系统的扰动可能与中更新世晚期的气候变化有关。碳酸盐岩风化剖面被U的近期迁移过程所影响，风化剖面中的每一个单元甚至每一个土样都具有复杂的历史。这些单元或者土样是古老的风化历史和近期的重新迁移过程的叠加。