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1.
赞比亚东北部伊鲁米德带是一个北东向延伸的中元古代构造活动带,起自赞比亚中部,向北东一直延伸至赞比亚-坦桑尼亚边境,并进入马拉维北部;其东北部以古元古代乌本迪构造带为界;西北部以班韦乌卢地块为界;西部和西南部受新元古代的达马拉-卢菲利安弧-赞比西构造事件的影响.Kachinga长石砂岩位于伊鲁米德带的东北部伊索卡南部.本文获得Kachinga长石砂岩的416颗碎屑锆石U-Pb年龄多集中在1749±25～1920±23Ma之间,Kachinga长石砂岩的形成时代可能晚于1331±26Ma,属于中元古代.Kachinga长石砂岩碎屑锆石CL图像表明,大部分锆石为岩浆结晶锆石,少部分锆石颗粒为增生-混合型锆石,表明其经历了多期构造-热事件的改造.锆石中存在有一部分磨圆度较好的颗粒,表明其经历了多次搬运和沉积过程,从而指示了古老沉积岩为Kachinga长石砂岩提供了物源.主量元素、微量元素和稀土元素构造环境判别及物源分析表明了Kachinga长石砂岩物源主要为上地壳大陆长英质源区,并且可能混有古老沉积物成分,物源区构造背景为大陆岛弧环境.  相似文献   

2.
山西吕梁山地区界河口岩群（后文简称界河口群）主要由一套变质砂泥质岩石组成,含有一定量的条带状大理岩、斜长角闪岩等。利用LA-ICP-MS对位于关帝山西榆皮、娄烦县杜交曲及云中山三角镇地区的含石榴黑云二长花岗片麻岩（12LL05-1）、片状黑云母石英岩（12LL09-2）和含石榴钾长石英岩（12LL15-1）进行锆石U-Pb年龄测定,获得的二长花岗片麻岩（12LL05-1）岩浆结晶年龄为1941±28Ma、片状黑云母石英岩（12LL09-2）碎屑锆石最小的峰值年龄为2519.5±6.7Ma及含石榴钾长石英岩（12LL15-1）碎屑锆石2个峰值年龄2143±15Ma和2599±11Ma。根据岩石组合和同位素测定结果推测,关帝山西榆皮地区的界河口群与界河口-汉高山一带的界河口群可以对比,沉积时代在1.94Ga之前;娄烦县杜交曲一带的界河口群可与五台岩群相对比,属新太古代;云中山三交镇一带的界河口群可与野鸡山群或岚河群相对比。沿岚县-方山-吕梁一线存在一条大型韧性剪切带,倾向NNW-NWW,表现为右行剪切的运动学性质,将吕梁山区近EW向构造带改造为NNE向。  相似文献   

3.
周喜文  耿元生 《岩石学报》2009,25(8):1843-1852
贺兰山孔兹岩系作为华北克拉通西部孔兹岩带的重要组成部分,其变质时代问题一直悬而未决.利用SHRIMP锆石U-Pb定年技术,对贺兰山孔兹岩系中3个代表性富铝片麻岩(石榴堇青钾长片麻岩、石榴堇青二长片麻岩与石榴黑云斜长片麻岩)样品进行了精确定年.发现这3种岩石虽处不同层位,但其碎屑锆石年龄却非常集中,各测点207Pb/206Pb年龄总体变化在2.0～2.1Ga之间,加权平均年龄则在2017～2040Ma之间.这些碎屑锆石都具有岩浆结构特征,反映当时曾存在大规模花岗质岩浆活动,所成岩体为孔兹岩系沉积提供了充足物源.另有少量大于2.5Ga的碎屑锆石(2520～2949Ma),表明本区存在太古代岩浆活动记录.本区石榴堇青二长片麻岩中发育典型的变质增生锆石,其成因很可能与黑云母的脱水熔融反应有关.利用该锆石确定贺兰山孔兹岩系的变质时代为1950±8Ma.该时代与东部大青山、乌拉山孔兹岩系变质时代相同,表明华北克拉通西部的阴山地块与鄂尔多斯地块大体是以平行的方式正面拼贴到一起的,形成了目前的孔兹岩带.  相似文献   

4.
山西吕梁山地区界河口岩群(后文简称界河口群)主要由一套变质砂泥质岩石组成,含有一定量的条带状大理岩、斜长角闪岩等。利用LA-ICP-MS对位于关帝山西榆皮、娄烦县杜交曲及云中山三角镇地区的含石榴黑云二长花岗片麻岩(12LL05-1)、片状黑云母石英岩(12LL09-2)和含石榴钾长石英岩(12LL15-1)进行锆石U-Pb年龄测定,获得的二长花岗片麻岩(12LL05-1)岩浆结晶年龄为1941±28Ma、片状黑云母石英岩(12LL09-2)碎屑锆石最小的峰值年龄为2519.5±6.7Ma及含石榴钾长石英岩(12LL15-1)碎屑锆石2个峰值年龄2143±15Ma和2599±11Ma。根据岩石组合和同位素测定结果推测,关帝山西榆皮地区的界河口群与界河口—汉高山一带的界河口群可以对比,沉积时代在1.94Ga之前;娄烦县杜交曲一带的界河口群可与五台岩群相对比,属新太古代;云中山三交镇一带的界河口群可与野鸡山群或岚河群相对比。沿岚县—方山—吕梁一线存在一条大型韧性剪切带,倾向NNW-NWW,表现为右行剪切的运动学性质,将吕梁山区近EW向构造带改造为NNE向。  相似文献   

5.
在欧龙布鲁克地块东部地区的正片麻岩中识别出呈透镜状产出的基性麻粒岩,部分已转变为斜长角闪岩。其主要矿物组合为单斜辉石、斜方辉石、斜长石、角闪石等,为典型中低压麻粒岩相组合。锆石SHRIMP U-Pb定年得到基性麻粒岩1928±9Ma的变质年龄,片麻岩围岩得到了1927±20Ma的变质年龄,以及2368±5Ma、2377±7Ma的岩浆结晶年龄。片麻岩锆石Hf同位素数据显示变质锆石及岩浆锆石均具有相似的Hf同位素成分,其二阶段模式年龄为2590~2830Ma,显示其可能源于太古代地壳物质的再造。欧龙布鲁克地块古元古代岩浆及变质演化历史与塔里木克拉通及华北克拉通很高的相似性,预示着在古元古代三者可能具有一定的亲缘性。  相似文献   

6.
陕西小花岔铀矿床位于北秦岭造山带的东北部,矿体产于黑云母花岗伟晶岩和黑云斜长片麻岩的接触带同化混染区。为了厘定研究区花岗质岩浆演化与铀矿化作用的关系,对矿区内出露的花岗岩、花岗伟晶岩开展了详细的年代学和岩石地球化学研究。LA-ICP-MS锆石U-Pb定年结果表明:灰池子花岗岩体的形成年龄为(444±4.0)Ma;高山沟花岗岩株的形成年龄为(422±0.82)Ma;产铀黑云母花岗伟晶岩的形成年龄为(417±2.6)Ma;非含矿黑云母花岗伟晶岩的形成年龄为(413±1.8)Ma。地球化学数据表明:矿区花岗质岩石富集大离子亲石元素Rb、Ba、K,亏损高场强元素Nb、Ta。含矿黑云母花岗伟晶岩由于同化混染作用及与围岩的元素交换等原因,其基性组分Fe、Mg和挥发分F-含量较高,同一条黑云母花岗伟晶岩脉元素组成的差异是由于伟晶岩浆的同化分离结晶所致,在伟晶岩-黑云斜长片麻岩的接触带发生化学组分的元素交换,使得伟晶岩浆中U-F络合物发生分解,并且在良好的成矿条件下(围岩的铀含量较高、较好的构造环境)使得铀饱和沉淀形成铀矿物,如晶质铀矿等。小花岔铀矿床的形成主要受到了伟晶岩浆、围岩成分、岩浆热液中挥发分共同的作用,最终导致了铀矿床的形成。  相似文献   

7.
本文报道了华北克拉通西部大青山地区新太古代晚期变质深成侵入岩的锆石SHRIMP年龄。本文涉及的3个样品取自大青山的石拐南部,岩性为黑云母二长花岗质片麻岩、紫苏石英闪长质片麻岩和闪长质片麻岩。根据矿物组合,黑云母二长花岗质片麻岩和紫苏石英闪长质片麻岩遭受高角闪岩相-麻粒岩相变质,闪长质片麻岩遭受角闪岩相变质。锆石具核-幔-边或核-边结构。岩浆锆石年龄为2484±7Ma、2494±12Ma和2495±10Ma,考虑到岩石遭受后期构造热事件强烈改造,岩浆锆石发生不同程度变质重结晶,振荡环带变得模糊,年龄很可能偏年轻,岩浆锆石真实的形成年龄应更大一些,形成于新太古代晚期。2个样品记录早期变质锆石年龄为2441±7Ma和2481±10Ma;2个样品记录晚期变质锆石年龄为1847±35Ma和为1919±73Ma。结合前人工作,可得出如下结论:1)石拐地区存在新太古代晚期二长花岗岩、石英闪长岩和闪长岩等不同类型变质深成侵入岩。新太古代晚期岩浆作用在整个大青山地区很可能广泛发育,古元古代晚期孔兹岩带是在太古宙基底之上或其邻区发展起来的。2)与大青山地区其它古元古代早期以前的地质体类似,新太古代晚期变质深成侵入岩普遍遭受古元古代早期和晚期构造热事件叠加改造。  相似文献   

8.
冀北红旗营子杂岩的锆石、独居石年代学及地质意义   总被引：19，自引：0，他引：19  
较为详细的SHRIMP、LA-ICPMS锆石U-pb年代学和独居石电子探针Th-U-b化学法定年揭示，隆化-山地块的石英闪长质片麻岩和石榴黑云二长花岗质片麻岩分别形成于2484Ma和2180Ma，同时存在3164～2553Ma的锆石记录和约1854Ma的变质改造事件；细粒二长花岗岩形成于413Ma，独居石内核记录了约628Ma的继承年龄。凤山-宁地块的钾长花岗质糜棱片麻岩、角闪黑云石英闪长质片麻岩和黑云母二长花岗岩分别形成于1876Ma、1838Ma和1810Ma，其中存在2042-1904Ma的捕获锆石，遭受了1756Ma、1694Ma和313．5Ma的多期改造，其中晚古生代的构造-浆-质事件的改造尤为强烈。赤城-礼地块的角闪黑云花岗闪长质片麻岩分别形成于2535Ma和2529-2480Ma，石榴英云闪长质片麻岩和石榴黑云斜长变粒岩分别形成于1871Ma和1841Ma，发现有约2602Ma的继承锆石，并记录了从古元古代到晚古生代多阶段的改造事件，尤其清楚地记录了343-320Ma的地质事件。结合前人的年代学资料，综合分析上述地质年代学的特征，认为红旗营子杂岩从东到西可能由不同来源的微陆块组成，这些微陆块都经历了晚古生代的构造-岩浆-变质事件，可能在古生代晚期才与华北克拉通北缘拼贴。  相似文献   

9.
赞比亚北部班韦乌卢地块演化及矿产资源研究现状   总被引：3，自引：0，他引：3  
赞比亚北部班韦乌卢地块受到古元古代乌本迪构造带、新元古代基巴拉构造带、新元古代伊鲁米德构造带及泛非期卢弗里安构造带的影响,主要分布有金、锰和金刚石矿床(点)。金矿床(点)主要赋存于姆波罗科索盆地东部姆巴拉组以紫红色砾岩—砂岩为主的碎屑沉积岩中,并且有较好的矿化线索。锰矿床主要分布在曼萨周围,可分为沉积型和构造型两类。班韦乌卢地块东部边缘发育含金刚石的钾镁煌斑岩和金伯利岩,在伊索卡地区前人利用重砂方法找到金刚石,推测地块内部可能寻找到含金刚石的钾镁煌斑岩和金伯利岩。因此,作者通过研究班韦乌卢地块的演化及其矿产资源现状,认为该地区具有较好的找矿潜力,可为中资矿业企业的矿权登记及矿产开发等方面提供基础的地质资料和科学依据,符合国家实施的矿产资源勘查开发"走出去"战略和"一带一路"战略。  相似文献   

10.
耿元生 《岩石学报》2009,25(8):1830-1842
位于华北克拉通西缘的贺兰山杂岩主要由孔兹岩系和变形花岗岩(正片麻岩)所组成,前者主要由夕线石榴片麻岩、石榴二长片麻岩、变粒岩和少量的大理岩及麻粒岩所组成,后者主要包括黑云斜长片麻岩、石榴子石花岗岩、斑状花岗岩和片麻状变质闪长岩.本文报道了该区变形花岗岩的锆石SHRIMP U-Pb定年结果.黑云二长片麻岩和石榴子石花岗岩分别形成于2053±58Ma和2047±42Ma,斑状花岗岩和片麻状闪长岩分别在1955Ma和1920Ma侵位.大量的年代学资料表明,在华北克拉通北缘存在一条古元古代晚期的花岗杂岩带,该带中的花岗杂岩主要形成于三个阶段,第一阶段大于2.0Ga,第二阶段主要出现在2.0～1.87Ga期间,第三阶段的花岗杂岩在1.85～1.80Ga期间侵位.年代学研究还表明,古元古代晚期的花岗岩浆作用常常与变质事件紧密相关.  相似文献   

11.
Police, politics, and the right to the city   总被引：1，自引：0，他引：1  
Mustafa Dikeç 《GeoJournal》2002,58(2-3):91-98
Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete.  相似文献   

12.
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.  相似文献   

13.
Clay subfractions (SFs) of <0.1, 0.1–0.2, 0.2–0.3, 0.3–0.6, 0.6–2 and 2–5 μm separated from Middle Riphean shales of the Debengda Formation are studied using the TEM, XRD, K-Ar and Rb-Sr isotopic methods. The oxygen and hydrogen isotope compositions in the SFs are studied as well. The low-temperature illite-smectite is dominant mineral in all the SFs except for the coarsest ones. The XRD, chemical and isotopic data imply that two generations of authigenic illite-smectite different in age are mixed in the SFs. The illite crystallinity index decreases in parallel with size diminishing of clay particles. As compared to coarser SFs, illite of fine-grained subfractions is enriched in Al relative to Fe and Mg, contains more K, and reveals higher K/Rb and Rb/Sr ratios. The Rb-Sr age calculated by means of the leachochron (“inner isochron”) method declines gradually from 1254-1272 Ma in the coarsest SFs to 1038-1044 Ma in finest ones, while the K-Ar age decreases simultaneously from 1225–1240 to 1080 Ma. The established positive correlation of δ18O and δD values with dimensions of clay particles in the SFs seems to be also consistent with the mixing systematics. The isotopic systematics along with data on mineral composition and morphology lead to the conclusion that mixedlayer illite-smectite was formed in the Debengda shales during two periods 1211–1272 and 1038–1080 Ma ago. The first period is likely close to the deposition time of sediments and corresponds to events of burial catagenesis, whereas the second one is correlative with the regional uplift and changes in hydrological regime during the pre-Khaipakh break in sedimentation.  相似文献   

14.
Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N2 in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area.  相似文献   

15.
马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多1000,成矿温度以中-低温为主。金属硫化物ε~(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,~(206)Pb/~(204)Pb为17.858~17.918:~(207)Pb/~(204)Pb为15.603~15.694;~(208)Pb/~(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra~1.05Ra,~(40)Ar/~(36)Ar为326.1~765.1,~(38)Ar/~(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ~(13)C_(CH_4)值为-36.01‰~-28.80‰,δ~(13)C_(C_2H_6)值为-27.72‰~-22.44‰,δ~(13)C_(CO_2)值为-23.24‰~-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。  相似文献   

16.
The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological (i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates) controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were <20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is lost to sediments.  相似文献   

17.
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18.
在野外地质调查的基础上,选取滹沱群豆村亚群底部四集庄组玄武岩、顶部青石村组玄武岩和东冶亚群中下部河边村组玄武岩,进行岩石学和地球化学研究。分析结果表明：玄武岩主量元素高TiO2、TFeO,低MgO,具有演化的基性岩浆的特征。稀土元素含量相对较高,具有弱—中等程度的轻稀土元素富集,中等程度的轻重稀土元素分异,轻微的Eu异常;玄武岩中Cr、Ni含量变化较大,但与Mg#具有很好的正相关性。微量元素配分图解中具有明显的Sr负异常,部分样品具有Nb、Ta和Ti负异常,无Zr、Hf负异常,与岛弧火山岩不同;同时Nb、Ta无分异,Zr/Hf值较高,具有板内玄武岩浆的特征。综合分析认为,滹沱群玄武岩可能形成于板内裂谷环境。在岩浆上升过程中发生橄榄石与尖晶石的分离结晶作用,同时不同程度地受到地壳的混染。  相似文献   

19.
The mineral composition of the Talatui gold deposit has been studied with modern methods. Previously unknown minerals (ilmenite, siegenite, glaucodot, wittichenite, matildite, hessite, pilsenite, zircon, tremolite, cummingtonite, hercynite, and goethite) have been identified in the ore. A high Re content has been detected in molybdenite. The spatiotemporal separation of Au and Ag is caused by different mineral species of these elements and their diachronous precipitation during the ore-forming process. Gold crystallized along with early mineral assemblages, beginning from virtually pure gold (the fineness is 996). Silver precipitated largely at the end of the process as hessite (Ag2Te) and matildite (AgBiS2). The temperature of ore deposition varied from 610 to 145°C, the pressure was 3370–110 bar, and the salt concentration ranged from 56.3 to 0.4 wt % NaCl equiv. The heterogeneous state (boiling) of fluid at the early stages has been documented. The chemical and isotopic compositions of the fluid testify to its magmatic nature and the participation of meteoric water at late stages in the ore-forming process. Thermodynamic modeling reproduces the main specific features of ore formation, including separation of Au and Ag. A physicochemical model of the gold mineralization in the Darasun ore district has been proposed. On the basis of several attributes, the Talatui deposit has been referred to the prophyry gold-copper economic type.  相似文献   

20.
岑巩县羊桥乡罗家塘杷榔组仅出露中-上部地层,岩性单一,均为青灰、灰绿色粉砂质泥、页岩.在其上部层位发现了俞氏贵州始海百合(Guizhoueocrinus yui Zhao,Parsley et Peng,2007),计有棘皮动物始海百合、腕足动物、软体动物-软舌螺、节肢动物-三叶虫等8属9种,包括了2个未定名的新种和1...  相似文献   

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