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   isotopic age data 的翻译结果: 查询用时:0.037秒
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isotopic age data
相关语句
  同位素年龄数据
     Comment on the Isotopic Age Data of Basement Metamorphic Rocks in Cathaysia Block
     华夏地块基底变质岩同位素年龄数据评述
短句来源
     A number of rock chemical data and 21 isotopic age data (Himalayan, 23-48 Ma) of intrusive rocks have been obtained, indicating syncollision in the south and post-orogenic extension in the north during the Himalayan stage.
     岩浆侵入岩获得一批岩石化学资料和21个喜马拉雅期的同位素年龄数据(23~48Ma),显示南部同碰撞、北部造山后拉张的特点。
短句来源
     Six age data(7.02~225.81kaBP) in Quaternary strata and four isotopic age data(169~130 Ma)of intrusive rocks have been obtained,and the study of a number of lithogeochemical data is indicated that magma rocks in the mapping area characterize arc magma rock.
     第四纪地层中获得了6个年龄数据(7.02~225.81 kaBP),侵入岩中获得4个同位素年龄数据(169~130 Ma);
短句来源
     In the present paper, the eight isotopic age data of four alkaline rock bodies (Miaoya, Shaxiongdong, Guanzishan and Huashanzhai) located in northern Hubei Province are first reported. Determined by U-Pb, K-Ar and Rb-Sr methods, these data range from 213 to 306 Ma. It is therefore safe to say that these bodies were formed in Hercynian-Indosinian Period.
     本文首次报导了湖北北部四个碱性岩体(庙垭、杀熊洞、观子山和花山寨)的8个同位素年龄数据,这些数据采用U-Pb、K-Ar和Rb-Sr法测定,其变化范围在213—306百万年之间,因此可以判定它们均形成于海西——印支期。
短句来源
     Owing to lack of formation temperature data of mylonites,such problems as the formation depth,metamorphic evolution,deformation mechanism,exhumation history of mylonites,relation with host rocks and explanation of isotopic age data are difficult to interpret correctly and reasonably.
     在缺少糜棱岩形成温度资料的情况下,糜棱岩的形成深度、与所叠加岩石的关系、变质演化、抬升-剥露历史、矿物的变形机制、同位素年龄数据的解释等一系列问题就很难得到正确合理的解释。
短句来源
  同位素年代数据
     The major geological events succession of this area has been estalished based on the existing isotopic age data and field observations.
     就现有同位素年代数据和野外产状建立了本区主要地质事件的序列。
短句来源
  “isotopic age data”译为未确定词的双语例句
     Based on the isotopic age data: U-Pb is 1 768Ma, 1 717Ma;
     三座庙序列侵入岩U—Pb法一致曲线年龄值1708Ma、1717Ma;
短句来源
     The probability analysis,clusting method and trend method are applied to study the distribution of isotopic age data of granitic rocks in time and space.
     本文应用概率分析,聚类分析和趋势分析方法研究了华南花岗岩年龄值的时空分布。 花岗岩年龄值的概率分析表明花岗岩的形成作用呈现周期性和旋迥性。
短句来源
     (5)the reexamination of geological significance of the obtained isotopic age data;
     (5 )已有同位素测年数据确切的地质意义 ;
短句来源
     Based on studies of styles of structural deformation types of sedimental formations and isotopic age data, the orogeny in the Alaides can be divided into five stages according to the time sequences: (1) the Kanas orogeny, which represents the early compression event as evidenced by the angular unconformity between the Habahe Group (Z-O_2) and the Baihaba Group (O_3);
     变形式样、建造类型及同位素年代学数据研究表明,阿尔泰造山带依次经历了5期构造运动,即:喀纳斯运动,形成白哈巴组(O_3)与哈巴河群(Z—O_2)间的角度不整合;
短句来源
     Based on new isotopic age data, the age of the Precambrian-Cambrian boundary should now be 597 Ma.
     根据同位素年龄测定的最新结果,提出前寒武系-寒武系界线年龄值为597Ma。
短句来源
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  isotopic age data
In this paper the interpretation of isotopic age data is discussed.
      
Isotopic age data suggest the presence in Madagascar of Archaean, Early and Mid-Proterozoic crustal material that was extensively reworked in Pan-African times.
      
Isotopic age data suggest the presence in Madagascar of Archaean, Early and Mid-Proterozoic crustal material that was extensively reworked in Pan-African times.
      
Rb-Sr and U-Pb isotopic studies of the two contrasting granite types of the Daguzhai and Luobuli massifs in South China provide new constraints on the interpretation of isotopic age data for plutonic igneous rocks.
      
These younger belts enable in general more precisely constrained isotopic age data for both hydrothermal and magmatic activity.
      
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With the help of the Periogram, isotopic age data of China have been

措助“周期图”法研究了中国大陆同位素年龄资料,初步结果表明: 1.存在着7个隐蔽周期:2040m.y.(百万年)、160m.y.、145.5m.y.、99m.y.、69.3m.y.、56.8m.y.和52m.y.。2.这些隐蔽周期的发展过程与中国地质年代表相吻合。

Ⅰ. Stratigaphic Summary The Yangjiaping section in Shimen County is located in the northern border of Hunan Province. Geotectonically it lies on the northern limb of Dongshanfeng anticlinorium of the southern margin of Yangtze platform. In tthis section the Precambrian system is well developed, and the upper and lower boundaries, are well defined. I is stratigraphical sequence is continuous and the geological structure is simple, while a lot of stromato-lites, microfossils, and small shelly fossils can be collected...

Ⅰ. Stratigaphic Summary The Yangjiaping section in Shimen County is located in the northern border of Hunan Province. Geotectonically it lies on the northern limb of Dongshanfeng anticlinorium of the southern margin of Yangtze platform. In tthis section the Precambrian system is well developed, and the upper and lower boundaries, are well defined. I is stratigraphical sequence is continuous and the geological structure is simple, while a lot of stromato-lites, microfossils, and small shelly fossils can be collected in this section. The total thickness is 1193. 34m. This section can be divided as follows: Overlying strata; lower cambrian Yangjiaping Formation Conformity Upper Sinian Dengying Formaton 176. 44m. in thickness. Upper Member, greyish white, lightgrey midium to thick bedded micro-litic dolomite, Clastic dolomite silicified muddy clastic dolomite, Sparry clastic dolomite. 69. 67m. Lower Member, dark grey thin-midium bedded microlitic dolomite, Siliceous dolomite, calcareous dolomite. 106. 77m. Conformity Upper Sinian Doushantuo Formation 475. 68m. Upper Member; grey, greyish-white midium thick micro-granular clastic dolomite, phosphoric calcium-bearing dolomite, intercalated with a few dolomitic limestone, phosphorite. 84. 53m. Lower Member; greyish black thin bedded micrite micro-granular car-bonaceous dolomite, dolomitic limestone, calcareous dolomite and a few pelitic siltstone, sandstone, carbonaceous slaty shale. 391. 15m. Conformity Lower Sinian Nantou Formation 719. 77m. Upper Member; grey massive morainic arenaceous mudstone, gompho- lite and siltstone with morainic pebbles. 68. 24m. Lower Member; dark grey massive arenaceous mudstone with mora-inic pebbles and a few pebbles-bearing sandstone intercalcated with slaty shale. 11. 53m. Conformity Lower Sinian Xiangmeng Formation 11. 93m. Dark-grey, greyish black slaty shale, carbonaceous slaty shale, Mn-bearing slaty shale intercalated with lens of dolomite. Conformity Lower Sinian Dongshanfeng Formaton 3. 7m. Dark-grey massive arenaceous slate with morainie pebbles, pebbles-bearing sandstone. Disconformity (Xuefeng movement) Presinian Banxi Group Xieshuihe Formation 260. 07m. Upper Member; purplish red, greyish green thick bedded medium-coarse granular slight metamorphic feldspathic quartz-sandstone, quartzose-sand-stone, siltstone, arenaceous slate and slate. 97. 60m. Lower Member; purplish red, greyish white quartzose conglomerate, arenaceous conglomerate, pebbles-bearing sandstone, coarse granular qu-artz-sandstone intercalated with a few quartz-siltstone and slate. 162. 47m. Conformity Presinian Banxi Group Madiyi Formation 175. 50m. Upper Member; purplish red, greyish green medium-thick bedded sli-ght metamorphic medium-fine granular quartz-sandstone, rudaceous sand-stone, siltstone.slate etc. 159. 37m. Lower Member; purplish red thick bedded massive slight metamorphic quartzose conglomerate, arenaceous conglomerate, pebbles-bearing sands-tone, coarse sandstone intercalated with a few arenaceous slate. 16. 13m. Unconformity (Wuling movement) Underlying strata; presinian Lengjiaxi Group. Ⅱ. Geochemical characteristics of rocks The geochemical characteristics of rocks of precambrian system in Yangjiaping section may be mentioned as follows: 1. Si. Al. Ca. Mg. K. Na. Fe. being the pretty high content chemi-cal elements, may be further subdivided into four assemblages, i. e. Al. Ti. B. Fe. Mn; Si. K. Ba. Cu. Pb; Ca. Mg. Na. P. Sr; and Cr. Ni Co. V. Zn. 2. Elements with closely correlative relationships are: Mn-B-Al-Ti; Sr-P-Ca-Mg; Cr-Ni-V; and Ba-Cu-Pb. 3. Variables of CaO-MgO and TiO_2-Fe_2O_3-K_2O-Al_2O_3-Na_2O respecti-vely control the carbonate rocks and the silicate rocks and both of them are in reverse relation which have been throughout the course proved by the mathematical method of factor analysis. 4. The result of the cluster analysis shows that the Fe_2O_3-Al_2O_3-K_2O- TiO_2-Na_2O can be clustered together, and represents the clay-rock, siltsto-ne and sandstone with pretty high content of the feldspar, while the FeO and MnO can be clustered together and represents the carbonate rocks. Ⅲ. Palaeomagnetic characteristics of rocks The palaeomagnetic characteristics of upper precarmbrian system at Yangjiaping section are as follows: 1. During the time of sedimentation of Precambrian rocks the palaeo-magnetism was basically located in the normal polarity epoch. The average palaeolatitude of Madiyi Formation, Xieshuihe Formation, Dongshanfeng Formation, Xiangmeng Formation, Nantuo Formation, Doushantuo Forma-tion and Dengying Formation were 30.49°, 19.93°, 12.25°, 23.32°, 9.84°, -20.20°, -19.46°, respectively. 2. There were three times of polar reversion during the deposition of precambrian rocks. One of the three times happened at the base of Cam-brian, and it may be served the proof of the boundary of Sinian and cam-brian systems, the other two occured in Madiyi Formation of Banxi Group and its cause of formation needs further research. 3. By comparing Upper precambrian Apw path at Yangjiaping section with that of Yangtze gorges, an Upper Precambrian Apw path at studied area has preliminaryly been set up. Ⅳ. Palaeontological characteristics There are chiefly micropaleoflora, stromatolites, and a few trace fossils in the Precambrian system of Yangjiaping section, the micropaleoflora may be subdivided into two assemblages: Banxi group-lower Sinian system consists of the first assemblage, They belong to unicellular alage Sphaeromorphitae (being the dominant eleme-nts) and numerous fragments of brown algae, among them, the sphaerical forms are dominant, and fibre fragments are secondary, and a few triangu-lar, quadrate or irregular forms, the diameters of most individuals are large than 50μ with coarse surfaces and simple-complicated ornament. The second assemblage consists of the micropaleoflora of Upper Sinian system, presenting acantomorphitae and a few elements of new genera and species of prismatomorphitae and Lophosphaeridium yichangense, Hubeis- phaera sp., which have never been seen in the first assemblage. The stromatolites are distributed in Doushantuo Formation and Dengy-ing Formation. In these formations the main elements; Nucleelo f., Boxonia f., Gymnosolen f., Baicalia f., etc. are dominant. The trace fossils consist of some irregular tubular bodies. V. Paleoglaciers The glacier periods of early Sinian may further be subdivided into two subglacier periods and an inter-glacier period. The Nantuo Formation is typical sedimentary type of morainic facies. The Xiangmeng Formation is the deposits of Xiangmeng inter glacier Period. The Dongshanfeng form-ation is pretty typical sedimentary type of glaciomarine facies. The Com-mon characteristics of the two types of glacier sediments are as follo-ws. 1. The contents of moraine are complicate but the main compositions are basically identical. 2. The shapes of pebbles are various but the chief outlines, Sphericiti-es and roundnesses are similar. 3. The uneven distribution, different sizes, random arrangements, great changes in longitudinal distribution and without definite rules are characters of pebbles. 4. The Striae, carve-traces, pressed crevasses, pressed pit., slide tra-cks and grinding pebbles are all present. The differences of the two types of the glacier sediments are: 1. The thickness of glacier marine deposit is rather stable and with a few intercalated beds that reveals the characteristics of marine deposit. but the thickness of morainic facies deposit varies greatly, intercalated beds almost absent, bedding also invisible. 2. There are litlle quantities of pebbles in glaciermarine deposit and with few boulders, ice slide tracks and grinding pebbles. The falling stone structures are well developed. On the contrary, the pebbles of morainic facies are very much with a definite of boulders. The ice slide tracks and grinding pebbles are generally seen, without falling stone-structures. Ⅵ. Sedimentary facies 1. The lower member of madiyi Formation is of meanderring river de-posit, and the upper member is of tidal flat deposit of river mouth gulf. 2. The lower member of Xieshuihe Formation is of the deposit of braided river, The upper member is of tidal flat deposit of river mouth gulf. 3. The Dongshanfeng Formation is the deposit of glacialmarine. 4. The Xiangmeng Formation is the deposit of subtidal gulf. 5. The lower member of Nantou Formation is the deposit of glacier-marine, the upper member is deposit of moraine. 6. The lower member of Doushantuo Formation represents the deposit of subtidal basin, the upper member is the deposit of subtidal flat carbo-nate rock. 7. The lower part of Dengying Formation represents the deposit of subtidal half closed flat shallow beach and interbeach, the upper member is the deposit of subtidal flat margin gradient. Based on the characteristics of isotopic age data, paleontology, crustal movement, and paleoglacier, the Precambrian System may be correlated as follows: The Yangjiaping Formation rich in small shelly fossils is the equivale-nce of Tianzhushan Formation in east of the Yangtze Gorges, the Meishu-cun Formation in eastern Yunnan, the Maidiping Formation in Sichu-an. The upper morainic Nantou formation may be correlated with Nantou formation in Yunnan and in east of the Yangtze Gorges, Silikou Forma-tion North of Guangsi, Leigongwu Formation in Western Zejiang and Nor-theast of Jiangsi. The lower Morainic Dongshanfeng Formation is the equivalence of Gucheng Formation in Changyang, Hubei, the Changan Formation-lover Member of Fulu Formation in eastern Guizhou and Guangsi. The Xueshuihe Formation is suitable to be correlated with the Liantuo Formation east of the Yangtze Gorges, the Qingshuijiang Formation-Rongli Formation east of Guizhou, Gongdong Formation, north, of Guangsi, Kaiji-anqiao formation in southwestern Sichuan. The Madiyi Formation may be correlated with Jialu Formation, Fan-shao Formation of eastern Guizhou. Baizhu Formation, Hetong Formation of Northern Guangsi. the Suxiong Formation of southwestern Sichuan. The Lengjiaxi Group may be correlated with the Fanjingshan group of eastern Guizhou, the Sibao group of Northern Guangsi, the Kunyang group of eastern Yunnan, the Ebian group of southwestern Sichuan, the Sandouping group of the eastern Yangtze G

一、地层剖面剖面全长2公里,出露较好,构造简单,层序连续完整,顶、底界接触关系清晰,产较丰富的微古植物、叠层石、小壳动物等古生物化石,可分一群、一系、两统、七组。地层总厚度为1193.34米。自上而下分为: 上覆地层:下寒武统杨家坪组黑色炭质页岩与薄层硅质岩互层。整合震旦系灯影组 176.44米上部:由灰白色、浅灰色中—厚层粉晶云岩、粒屑云岩、硅化泥晶云岩、亮晶粒屑云岩等组成。 69.67米下部:由深灰色薄—中厚层泥—粉晶云岩、硅质云岩、灰质云岩等组成。 106.77米整合陡山沱组 475.68米上部:由灰色、灰白色中—厚层状粉晶粒屑含灰质云岩、含磷质云岩、含硅质云岩夹少量白云质灰岩、磷块岩等组成。 84.53米下部:由灰黑色薄层泥晶—粉晶炭质云岩、白云质灰岩、灰质云岩及少量泥质粉砂岩、砂岩、炭质板状页岩等组成。 391.15米整合南沱组 90.02米上部:由冰碛砾砂质泥岩、冰碛砾泥岩及冰碛砾粉砂岩等组成。 78.49米下部:由深灰色冰碛砾砂质板岩、冰碛砾板岩及少许冰碛砾砂岩、板状页岩等组成。 11.53米整合湘锰组:由深灰色、灰黑色板状页岩、炭质板状页岩、含锰板状页岩及夹白云岩透镜体等组成。 11.93米整...

一、地层剖面剖面全长2公里,出露较好,构造简单,层序连续完整,顶、底界接触关系清晰,产较丰富的微古植物、叠层石、小壳动物等古生物化石,可分一群、一系、两统、七组。地层总厚度为1193.34米。自上而下分为: 上覆地层:下寒武统杨家坪组黑色炭质页岩与薄层硅质岩互层。整合震旦系灯影组 176.44米上部:由灰白色、浅灰色中—厚层粉晶云岩、粒屑云岩、硅化泥晶云岩、亮晶粒屑云岩等组成。 69.67米下部:由深灰色薄—中厚层泥—粉晶云岩、硅质云岩、灰质云岩等组成。 106.77米整合陡山沱组 475.68米上部:由灰色、灰白色中—厚层状粉晶粒屑含灰质云岩、含磷质云岩、含硅质云岩夹少量白云质灰岩、磷块岩等组成。 84.53米下部:由灰黑色薄层泥晶—粉晶炭质云岩、白云质灰岩、灰质云岩及少量泥质粉砂岩、砂岩、炭质板状页岩等组成。 391.15米整合南沱组 90.02米上部:由冰碛砾砂质泥岩、冰碛砾泥岩及冰碛砾粉砂岩等组成。 78.49米下部:由深灰色冰碛砾砂质板岩、冰碛砾板岩及少许冰碛砾砂岩、板状页岩等组成。 11.53米整合湘锰组:由深灰色、灰黑色板状页岩、炭质板状页岩、含锰板状页岩及夹白云岩透镜体等组成。 11.93米整合东山峰组:由深灰色、灰色块状含冰碛砾石砂质板岩、含冰碛砾石砂岩等组成。3.70米假整合板溪群渫水河组 260.10米上段:由紫红色、灰绿色粗—细粒浅变质长石石英砂岩、石英砂岩、粉砂岩、砂质板岩、板岩等组成。 97.60米下段:由紫红色、灰白色厚层—块状变质石英砾岩、砂砾岩、含砾砂岩、粗粒石英砂岩夹少量石英粉砂岩、板岩等组成。 162.47米整合马底驿组 175.50米上段:由紫红色、灰绿色中—厚层状浅变质中—细粒石英砂岩、长石石英砂岩、含云母砂岩、粉砂岩、板岩等组成。 159.37米下段:由紫红色厚层—块状变质石英砾岩、砂砾岩、含砾砂岩、石英粗砂岩夹少量砂质板岩等组成。 16.13米不整合下伏地层:冷家溪群变质砂岩、板岩互层。二、岩石地球化学据1395个岩石光谱样、47个化学样的分析数据,用因子分析、聚类分析研究了各类岩石地球化学分类、元素间相关关系;用有序地质体最优分割法及对分移动窗口法研究了剖面上层序的划分。初步掌握了该剖面地球化学特征如下: 1.平均化学成分以Si、Al、Ca、Mg、K、Na、Fe为主,可划归A1、Ti、B、Fe、Mn;Si、K、Ba、Cu、Pb;Ca、Mg、Na、P、Sr;Cr、Ni、Co、V、Zn等组合。 2.元素相关关系较密切的有Mn-B-A1-Ti;Sr-P-Ca-Mg;Cr-Ni-V;Ba-Cu-Pb等,其中尤以Si、P、Ca、Mg关系密切。 3.元素丰度在时间上的演化规律与剖面上地层划分基本上相吻合。 4.因子分析表明变量CaO—MgO控制碳酸盐岩;变量TiO_2—Fe_2O_3—K_2O—A1_2O_3—Na_2O控制硅酸盐岩,且两者始终保持反间关系。 5.聚类分析表明Fe_2O_3、Al_2O_3、K_2O、TiO_2、Na_2O聚类一起,代表了粘土岩、粉砂岩、含长石较高的砂岩类;FeO、MnO聚集一起,反映了还原条件下形成的岩石;CaO、MgO聚类一起,代表了碳酸盐岩类岩石。三、古地磁据30个样品的磁测数据,获得了磁性地层的初步成果如下: 1.晚前寒武纪沉积期,基本上处于正极性时期,同时均处于低纬度地带,其中马底驿组平均古纬度为30.49°,渫水河组为19.93°,东山峰组为12.25°,湘锰组为23.32°,南沱组为9.84°,陡山沱组为-20.20°,灯影组为-19.46°。 2.晚前寒武纪沉积期,经历了三次极性倒转,其中寒武系底部求得的北磁极落在南半球的东经62.72°,南纬8.67°,该次极性倒转可作为震旦系与寒武系分界的佐证。另两次极性倒转发生在马底驿组沉积期内,其成因尚待进一步研究解释。 3.视古地磁极迁移轨迹表明,距今1000百万年前冷家溪群开始,地磁极位置从163.42°东、65.42°北起向西北方向迁移;板溪群时期,则在北极点附近绕动,而后向北西方向迁移;震旦纪时,磁极位置由早—晚,由5.65°—327.60°东、47.05°—39.00°北之间绕动。由于经验不够,又因受仪器设备限制,精度尚待进一步深化。但作为资料积累,对建立南方晚前寒武纪古地磁年表无疑将是有益的。四、古生物主要为微古植物、叠层石及一些虫迹化石。微古植物可建立两个组合:板溪群—下震旦统中微古植物为第一组合,是以球藻亚群为主的单细胞藻类及一些褐藻碎片,形态多为球形,其次为纤维状碎片,少数为三角形、方形及不规则形状,多数个体大于50微米,表面粗糙,有简单—复杂的纹饰。该组合近似蓟县青白口系及峡东莲沱组—南沱组中微古植物特征。上震旦统微古植物为第二组合,它除了继承下震旦统及板溪群中微古植物的许多分子外,更重要的是出现了刺球藻亚群及棱面藻亚群中少数分子及前所未见的Lophosphaerium yichangense, Hubeisphaera sp.等新属新种。该组合和南方各地上震旦统微古植物特征基本一致。叠层石产于陡山沱组及灯影组,主要为Nucleela f., Boxonia f., Gymnosolen f., Baicalia f. 等。虫迹化石较普遍,主要为一些不规则形管状体。五、古冰川统称早震旦世冰期,可进一步划分两亚冰期及一间冰期。南沱组代表南沱亚冰期沉积,为较典型的冰碛相沉积类型;湘锰组代表湘锰间冰期沉积;东山峰组代表江口组亚冰期沉积,为较典型的冰海沉积类型。两种沉积类型具有如下的共性: 1.冰碛物成分复杂,随地而异,但砾石的主要组分基本相同。 2.砾石的形状多种多样,但主要形态、球度及圆度相近似。 3.砾石分布不均匀,大小不一,排列杂乱,在纵向分布上,变化急剧,无一定规律。 4.均具有条痕、刻痕、压裂、压坑等冰溜遗痕及研磨砾石。上述共性说明冰海相与冰碛相有相近的亲缘关系。两种沉积类型有如下差别: 1.冰海相沉积厚度较稳定,具有少量夹层,其层理显示海相沉积特征;冰碛相沉积厚度变化大,几乎无夹层,不显层理。 2.冰海相沉积砾石数量少,大砾石少,冰溜遗痕及研磨砾石少见,落石构造非常普遍;冰碛相沉积砾石数量多,有一定数量大砾石,冰溜遗痕及研磨砾石普见,无落石构造。上述差异的原因,主要与冰川进入海洋的部位有关。六、沉积相共划分了3相组、4相、7亚相、16微相及62相段: 1.马底驿组沉积相下段曲流河沉积:结构成熟度低,杂基—颗粒支撑,板状及平行层理为主,剖面二元结构明显,粒度分析多数样品落在河流范畴。上段河口湾潮坪沉积:结构成熟度低,楔状、槽状、脉状再作用面、人字形等层理及波痕、泥裂大量出现,薄互层发育,粒度分析多数样品落在海(湖)滩范畴,部分样品落在河流范畴。 2.渫水河组沉积相下段辫状河流沉积:矿物及结构成熟度均较低,颗粒支撑为主,大型楔状、槽状交错层理发育,剖面二元结构发育不全,绝大多数样品落在费里德曼标准偏差散点图河流范畴。上段河口湾潮坪沉积:结构成熟度较低,杂基支撑,楔状、槽状、爬升、脉状、鱼骨状等层理及波痕、泥裂普见,薄互层发育,粒度分析结果,样品一半落在海洋,另一半落在河流范畴。 3.东山峰组冰海相沉积:矿物及结构成熟度低,杂基支撑,具微层理,落石构造发育,粒度分析参数值反映为中值,变化范围大,峰态及标准偏差变化范围小,偏度全为负偏。 4.湘锰组河口湾潮下海湾沉积:富含有机质、藻类及硫化物,常夹含锰碳酸盐岩及锰矿层,细纹状水平层理发育。 5.南沱组沉积相下段与东山峰组沉积相类似,为冰海相沉积,上段为冰碛相沉积。矿物及结构成熟度低,杂基支撑,不显层理,冰溜遗痕及研磨砾石普见,粒度参数值反映峰态中等—尖窄,偏度为极负偏。 6.陡山沱组沉积相下部浅海台地潮上—潮间—潮上带沉积:富含有机质、藻类及硫化物,岩石化学成分中Fe~(3+)/Fe~(2+) <1,微量元素Rb/K=0.0037,水平层理发育。上部浅海台地碳酸盐岩潮坪沉积:富含藻叠层石,岩石化学成分Fe~(3+)/Fe~(2+)<1,Rb/K=15.30,平行层理为主,局部有小—中型楔状交错层理。 7.灯影组沉积相下部浅海台地潮间—潮上带沉积:富含藻叠层石,钙球藻及少量藻丝体,泥—粉晶结构,水平层理为主,条纹状及网格状泥裂发育。上部浅海台地潮间—缘斜坡—盆地边缘:富含大型柱状叠层石,常见圆形或椭圆形、竹叶状砂屑、砾屑,具有大型滑动构造及包卷层理。七、划分与对比 (一)划分 1.震旦系与寒武系界线(顶界) 分界的主要依据为小壳动物群,已于188层炭质页岩与薄层硅质岩中发现:Protohertzina sp., P. unguliformis, P. anabarica, Turcutheca sp., Torellella sp. 等,此外尚见Oxe-aklostera monaxon等海绵骨针、微型海绵骨针及分类位置尚存疑的蚕形、球形类化石,其中Protohertzina sp., 为钱逸建立的早寒武世早期小壳化石带第一组合中的分子。其二,同时于188—190层中发现极为丰富的微古生物化石,计有蓝藻门、绿藻门、红藻门、细菌、疑源类及分类位置不明的藻微化石,共18属、19种(内3个新属、9个新种、9个未定种、2个未命名化石),它们保存好,属种类型复杂,除少数分子分别见于云南、四川下寒武统梅树村组、麦地坪组外,多数分子亦为首次发现,是国内已发现的相当层位微化石最特殊的类型,且与震旦系上统的微古化石组合有明显差异。其三,在震旦系顶部(187层)云岩中发现有虫管化石。综上三者依据对湖南湘西北地区震旦系与寒武系界线的划分和对比进行了论述,并将其界线置于产小壳化石的188层之底部。 2.板溪群与冷家溪群界线(底界) 界线置于1与0_2层之间,划分的主要依据为: (1)板溪群与冷家溪群呈高角度不整合接触,为一理想界面。 (2)冷家溪群为复理石建造,板溪群为类磨拉石建造。 (3)B、P、K、Cr、V、Sr等元素在冷家溪群顶部出现低值,进入板溪群后则出现高值。 (4)冷家溪群多数分子为一些形状简单、个体微小、膜壳较薄、表面光滑的球形藻类。板溪群多数分子则为形状较复杂、个体较大、膜壳较厚、表面具纹饰的藻类。 3.震旦系与板溪群界线界线置于102与103层之间,主要依据为古气候标志,即将冰成地层置于震旦系底部,这种意见的理由为: (1)早震旦世冰成地层遍布五大洲,便于世界对比。 (2)峡东震旦系经历了两次构造运动,缺失不少地层,如以冰成地层为底界,可摈除其中较大的一次构造运动的影响。 (3)如以莲沱组为底界,震旦纪时限大于2亿年,如从冰成地层开始,震旦纪时限小于1.5亿年,更符合建立新纪的时限要求。 (二)对比对比的依据主要是同位素、古生物及构造运动、古冰川,其次可考虑沉积建造、变质程度、岩性组合等因素。据此可作如

With the deveiopment of the methods of the determination of isotopic age, various new processes are established and hence the data of various geological ages are rapidly increasing. Howevet, a great number of data are not able to provide for further geological information becanse the basis theoretical study of the treat- ment of isotopic age does not meet the demand of present environment and even the data themself are full of contradiction. For example, there are around four hundred isotopic age data...

With the deveiopment of the methods of the determination of isotopic age, various new processes are established and hence the data of various geological ages are rapidly increasing. Howevet, a great number of data are not able to provide for further geological information becanse the basis theoretical study of the treat- ment of isotopic age does not meet the demand of present environment and even the data themself are full of contradiction. For example, there are around four hundred isotopic age data in qinling but, combining with the study of regional geology, we have found that part of the data are obviously giving younger ages than it should be, especially in the region of old basement which leads to the difficulty for the correlation of stratigraphy or rock facies. The factors which brings about deviation of the isotopic age are various but, from the point of view of physics, we stress on the effect of thermal diffusion. In monomineral there are daughter isolope formed by radioactive decay and they are apt to diffuse from the interior to the outlier or from one mineral to another mineral due to thermal diffusion which results in the lose of daughter isotope. If the isotopic age is determined according to the ordinary calculation method, it will evidently give a younger age which is not consistent with the geological observa- tion. Careful study reveals that there exist two parts of curve relationship between a geological age which has suffered late thermal disturbance and the distance of the sample away from the contact of igneous body i.e. within a certain distance in the proximate of the thermal source, the distance is a lineal function of the radioactive mother-daughter and it turns to an index function further away from the thermal source. Hence the correction of one geological superfical age after thermal disturbance must be taken part in two stages i.e. the index equation and the lineal equation(detail deduction given in this paper).

本文结合国内外实际资料,探讨引起同位素地质年龄偏差的原因,主要是矿物的扩散作用,即单矿物里由于放射性衰变所形成的同位素子体,热散从矿物内部扩散到边部,从一种矿物散到另一种矿物,造成放射性子体的丢失。一个受后期热源扰动的地质体的年龄与样品距热源的距离,存在两部分曲线关系,距离热源较近的一段距离内,放射性母子体比值与距离呈直线关系,而后呈指数函数关系。据此,提出指数方程和直线方程进行年龄校正。

 
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