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1.
Resulting from U-Pb geochronological study, it has been found that the gabbro-amphibolites composing the Bureya (Turan) Terrane in the eastern part of the Central Asian Fold Belt are Early Paleozoic (Early Ordovician; 455 ± 1.5 Ma) in age rather than Late Proterozoic as was believed earlier. The gabbro-amphibolites and associated metabasalts are close to tholeiites of the intraoceanic island arcs in terms of the geochemical properties. It is suggested that the tectonic block composed of these rocks was initially a seafloor fragment that divided the Bureya and Argun terranes in the Early Paleozoic and was later tectonically incorporated into the modern structure of the Bureya Terrane as a result of Late Paleozoic and Mesozoic events. 相似文献
2.
The formation of manganese rocks and ores occurred during the whole geological history of the Earth. Five metallogenic epochs
(Early to Middle Proterozoic, Late Proterozoic, Early to Middle Paleozoic, Late Paleozoic, and Meso-Cenozoic) and 7 very important
phases (Early, Middle, and Late Proterozoic, Early to Middle Paleozoic, Late Paleozoic, Late Mesozoic, and Meso-Cenozoic)
can be distinguished. The phases of manganese ore genesis at many stratigraphic levels are closely related to the global climatic
and tectonic reconstructions (the breakup of the continent of Gondwana and periods of glaciations and aridization) and biotic
events (mass extinction of organisms). Based on carbon isotopic composition in manganese carbonates, participation of oxidized
organic carbon is established. 相似文献
3.
根据国内外发现的地洼区及其与铀成矿时代的关系,分为早元古代、中元古代、晚元古代、早古生代、晚古生代,中生代和新生代等7个不同时代的地洼区。铀的成矿富集,发生在地洼阶段激烈期向余动期的过渡时间内。元古代地洼区地壳固结早,铀成矿年龄值大,地洼余动期时间长。中新生代地洼区地壳固结晚,铀成矿年龄值小,地洼余动期时间较短。 相似文献
4.
太行山重力梯度带的形成与华北岩石圈减薄的时空差异性有关 总被引：18，自引：0，他引：18
通过对比华北太行山重力梯度带两侧新生代玄武岩及其中幔源包体的成分, 发现: (1)华北东、西部新生代玄武岩具有相反的演化趋势, 说明新生代以来西部岩石圈逐渐减薄, 而东部岩石圈逐渐加厚; (2)西部岩石圈地幔组成相对复杂, 年龄多为晚太古代-元古代; 而东部岩石圈地幔组成相对单一, 年龄多为现代值, 少数为元古代; (3)西部壳幔过渡带较厚而东部较薄, 反映两地不同的岩浆底侵作用程度.华北岩石圈组成的空间不均一性可能与岩石圈减薄过程的时空差异有关. 岩相古地理分析说明太行山重力梯度带的雏形形成于早白垩世, 与华北中生代岩浆活动的高峰相吻合.由于岩浆作用与岩石圈减薄作用密切相关, 因此认为华北岩石圈减薄的时空不均一性是形成太行山重力梯度带的重要机制. 相似文献
5.
东北地区前中生代构造演化及其与晚中生代盆地发育的关系 总被引：6，自引：1，他引：5
摘 要 东北地区前中生代构造演化可大致分为如下阶段：（1） 中、新元古代阶段;（2） 早古
生代加里东阶段;（3） 泥盆纪—早石炭世早华力西阶段;（4） 晚石炭世—三叠纪晚华力西—印
支阶段。多旋回构造演化使该区形成由多期褶皱带和多中间或边缘地块组成的 “镶嵌构造
区”并为晚中生代大型含油气盆地的发育奠定了基础。 相似文献
6.
地史中成矿演化的趋势和阶段性 总被引：8，自引：1，他引：8
大量的地质矿产资料表明，随着地球的形成和发展，尤其是水圈、大气圈和生物圈的演化，成矿作用也呈前进的、不可逆的发展趋势，表现在成矿物质（矿种）由少到多；矿床类型由简到繁；成矿频率由低到高；聚矿能力由弱到强。受地球上重大地质事件的制约，这一成矿演化过程又表现出阶段性，可划分出７个成矿大阶段，即太古宙、古元古代、中元古代、新元古代、早古生代、晚古生代—早中生代、晚中生代—新生代等成矿期。每一期中都有特定的成矿构造环境和矿床成因类型。制约地史上成矿演化的主要因素有：①成矿物质的地球化学性质；②水圈、大气圈和生物圈的演化；③地球构造运动的演变。矿床形成后的保存条件对矿床的时空分布特征也有重要影响。 相似文献
7.
秦岭造山带构造-成矿旋回与演化 总被引：5，自引：0，他引：5
构造与成矿活动是否具有旋回性是地质界长期争论的一个命题。本文根据矿床成矿系列理论和方法,论述了秦岭造山带构造-成矿活动,划分出新太古代-古元古代早期、古元古代晚期、中-新元古代、早古生代、晚古生代和中、新生代6个构造-成矿旋回,探讨了每个旋回的矿床成矿系列特征和成矿演化历史。指出该造山带的成矿作用既有长期性和连续性,也有间断性和旋回性;中、新元古代至早古生代和中、新生代两个时期是秦岭造山带中两个主要的成矿高峰期;构造-成矿作用可分为开裂、拼合及相对稳定三个阶段;成矿作用早期以幔源岩浆侵入及海相火山活动为主,晚期以壳幔混源-壳源的陆相中酸性岩浆侵入及火山活动为主;与火成活动及开裂作用有关的成矿活动在南、北两个成矿域之间具有振荡性演化的特征. 相似文献
8.
本文以内蒙古西部英巴地区一个典型剖面为例,开展了详细的构造解析和年代学研究,初步构建这一地区晚古生代-中生代的构造岩浆事件框架。这一地区至少发育三期岩浆活动和三期构造变形事件。锆石U-Pb定年结果和前人的资料显示,三期岩浆活动分别为石炭纪（325~313 Ma）的花岗闪长岩和花岗岩、早二叠世（291~277 Ma）的钾长花岗岩和中细粒花岗岩及早白垩世（~134~130 Ma）的伟晶岩和石英二长岩。第一期构造变形事件为NW-SE向挤压,发生在早二叠世之后,使花岗闪长岩和钾长花岗岩发生挤压变形,形成主体低角度北西倾的片麻理,局部发育同期褶皱,变形温度为450~600℃;第二期为NW-SE向伸展,大致发生在早白垩世,使片麻状花岗闪长岩和片麻状钾长花岗岩发生中高温（450~650℃）的糜棱岩化作用,形成南东倾的低角度韧性剪切带,具有正断性质,后被伟晶岩脉切穿。第三期为NW-SE向伸展,发生在早白垩世之后,形成北西倾的中角度脆性正断层,断距2~10米,并使伟晶岩变形为碎裂岩。 相似文献
10.
ZHOU Taofa YUE ShucangDepartment of Resources Environmental Science Hefei University of Technology Tunxi Roa Hefei Anhui 《《地质学报》英文版》2000,74(2):207-212
Studies of the Pb, Sr and Nd isotopic composition of Mesozoic intrusive rocks indicate that the basement of the copper-gold metallogenic belt of the middle and lower reaches of the Yangtze River has "two-layer structure" and partly has "multi-layered structure", and is inhomogeneous and shows the distinct feature of E-W provincialism. The calculated model lead ages (t1) are mostly greater than 2600 Ma, and the model neodymium ages (TDM) vary from 953 to 2276 Ma and concentrate in two time intervals: 1800-2000 Ma and 1200-1600 Ma. It is concluded that the basement of the MBYR is composed of the Late Archaeozoic to Middle Proterozoic metamorphic series and that the crust was initiated in the Archaean and continued to grow in the Early and Middle Proterozoic, and the proportion of new crust formed by mantle differentiation during the Late Proterozoic is low. 相似文献
11.
庐山隆起─滑脱构造 总被引：6，自引：2，他引：4
庐山隆起-滑脱构造呈不对称状,西部外壳宽,出露地层完整;东部外壳窄,缺失地层较多,其内核为-开阔短轴背形,由早元古代星子群深变质及晚元古代、早古生代、中生代花岗岩组成。外壳由中元古代双桥山群浅变质沉积岩和细碧-石英角斑岩,晚元古代汉阳峰组浅变质流纹岩、细碧岩,晚元古代辉绿岩,震旦纪及后震旦纪未变质地层组成。内核与外壳间的接合面原是早元古代星子群与中元古代双桥山群间的平行不整合面,但在庐山隆起-滑脱构造形成过程中,受到了顺层韧性剪切作用及其以后其它构造作用的改造和破坏。以接合面为界,外壳自内向外,顺层韧性剪切变形变质、顺层韧性剪切固态流动褶皱变形由强至弱发生变化,直至无变形变质;而内核从接合面附近向内部,退变质作用逐渐消失。庐山隆起-滑脱构造是在西部挤压,东部拉张的伸展构造环境中形成的,经历了吕梁期雏形（或基础）、晋宁-加里东期形成发展及海西-喜山期改造三个阶段。 相似文献
12.
宁芜盆地吉山铁矿床辉长闪长玢岩SHRIMP锆石U-Pb定年及其地质意义 总被引：1，自引：1，他引：0
吉山铁矿床是宁芜火山岩盆地中的重要矿床,矿体主要产于辉长闪长玢岩体内。对吉山辉长闪长玢岩体运用SHRIMP锆石U-Pb定年技术进行年龄测试,结果为(130.0±1.0) Ma,代表成岩年龄。结合地质事实与前人研究成果,推测吉山铁矿床的成矿时间约为130 Ma或稍后。年代学研究中出现的年龄值(1885±14) Ma,与扬子克拉通的基底年龄值相吻合,暗示宁芜地区可能存在古元古代基底。吉山辉长闪长玢岩成岩及玢岩型铁矿床成矿作用所对应的地球动力学背景为中生代发生的中国东部岩石圈大规模减薄事件。 相似文献
13.
A review of the 2500 Ma span of alkaline-ultramafic, potassic and carbonatitic magmatism in West Greenland 总被引：1，自引：0，他引：1
Kimberlites, carbonatites and ultramafic, mafic and potassic lamprophyres have been produced in West Greenland in recurrent events since the Archaean. Five distinct age groups are recognised: Archaean (>2500 Ma). Early Proterozoic (1700–1900 Ma), Middle Proterozoic (Gardar, c. 1100–1300 Ma), Late Proterozoic (600 Ma) and Mesozoic-Tertiary (200-30 Ma) The rocks comprise two large and four small carbonatite occurrences, four kimberlite dyke swarms, one lamproite dyke swarm and one lamproite pipe, one dyke swarm of potassic lamprophyre (shonkinite) and some ten dyke swarms of ultramafic lamprophyre and monchiquite. Geochemical data for the various rock groups are presented. Some of the carbonatites may represent relatively unmodified mantle-derived melts. The kimberlites range from primitive to differentiated compositions, and there are regional differences between kimberlites within Archaean and Proterozoic basement. The ultrapotassic lamproites and shonkinites have strong negative Nb spikes in their trace element spectra. The ultramafic and monchiquitic lamprophyres encompass a large compositional variation; however, several of the dyke swarms have individual chemical characters.
The rocks are very unevenly distributed in West Greenland, indicating a lithospheric control, probably by old weakness zones providing access to the surface. The kimberlites are considered to be mainly of asthenospheric derivation. The regional differences are interpreted in terms of melting with phlogopite as a residual phase, with smaller degrees of melting at deeper levels beneath the Archaean lithosphere than beneath the Proterozoic. The ultrapotassic lamproites and shonkinites occur almost exclusively within a continental collision zone with possible two-way subduction and they are interpreted as mainly of lithospheric derivation, with a contribution from a subducted slab. Data for the other rock types are equivocal.
Except for the Archaean rocks, the age groups can be related to major geotectonic events. The Early Proterozoic group is related to continental collision at 1850 Ma and subsequent rifting; the Middle Proterozoic group is related to continental rifting (Gardar) and the Mesozoic group is likewise related to continental rifting prior to continental break-up in the Tertiary. The 600 Ma kimberlites and carbonatite are envisaged as cratonic, extra-rift activity in relation to continental break-up and formation of the Iapetus ocean further south, perhaps with a common cause in a broad, impinging mantle plume. 相似文献
14.
The Thomson Orogen forms the northwestern segment of the Tasman Orogenic Zone. It was a tectonically active area with several episodes of deposition, deformation and plutonism from Cambrian to Carboniferous time.Only the northeastern part of the orogen is exposed; the remainder is covered by gently folded Permian and Mesozoic sediments of the Galilee, Cooper and Great Artesian Basins. Information on the concealed Thomson Orogen is available from geophysical surveys and petroleum exploration wells which have penetrated the Permian and Mesozoic cover.The boundaries of the Thomson Orogen with other tectonic units are concealed, but discordant trends suggest that they are abrupt. To the west, the orogen is bordered by Proterozoic structural blocks which form basement west of the northeast-trending Diamantina River Lineament. The most appropriate boundary with the Lachlan and Kanmantoo Orogens to the south is an arcuate line marking a distinct change in the direction of gravity trends. The north-northwest orientation of the northern part of the New England Orogen to the east cuts strongly across the dominant northeast trend of the Thomson Orogen.The Thomson Orogen developed as a tectonic entity in latest Proterozoic or Early Cambrian time when the former northern extension of the Adelaide Orogen * was truncated along the Muloorinna Ridge. Early Palaeozoic deposition was dominated by finegrained, quartz-rich clastic sediments. Cambrian carbonates accumulated in the southwest and a Cambro-Ordovician island arc was active in the north. Along the western margin of the orogen, sediments were probably laid down on downfaulted blocks of deformed Proterozoic rocks, with oceanic crust further to the east.A mid- to Late Ordovician orogeny which affected the whole of the Thomson Orogen marked the climax of its precratonic (orogenic) stage. The northeast structural trend of the orogen (parallel to its western boundary with the Precambrian craton) was imposed at this time and has controlled the orientation of later folding and faulting. Up to three generations of folding have been recognized and fine-grained metasediments exhibit a prominent slaty cleavage. Metamorphism was to the greenschist and amphibolite facies, the highest grade rocks being associated with synorogenic granodiorite batholiths in the north. Following deposition of Late Ordovician marine sediments at the eastern margin, emplacement of post-tectonic Late Silurian or Early Devonian batholiths ended the precratonic history of the Thomson Orogen.The subsequent transitional tectonic regime was characterized by deposition of Devonian to Early Carboniferous shallow marine and continental sediments including widespread red-beds and andesitic volcanics. The maximum marine transgression occurred in the early Middle Devonian. Localized folding affected the easternmost part of the Thomson Orogen at the end of Middle Devonian time and was followed by intrusion of Devono-Carboniferous granitic plutons. However, the terminal orogeny which deformed all Devonian to Early Carboniferous rocks of the orogen was of mid-Carboniferous age. It produced northeast-trending open folds and normal and high-angle reverse faults which are considered to reflect basement structures. The cratonization of the Thomson Orogen was completed with the emplacement of Late Carboniferous granites and the eruption of comagmatic volcanics in the northeast, permian and Mesozoic sediments accumulated in broad, relatively shallow down warps which covered most of the former orogen. 相似文献
15.
《China Geology》2018,1(1):84-108
There are large volumes of the Phanerozoic granitoid rocks in China and neighboring areas. In recent years, numerous new and precise U-Pb zircon ages have been published for these granitoids, and define many important magmatic events, such as ca. 500 Ma granitoid events in the West Junggar, Altai orogens in the NW China, and Qinling orogen in the central China. These ages accurately constrain the time of important Early Paleozoic, Late Paleozoic, Early Mesozoic and Late Mesozoic magmatic events of the northern, central, western, southern and eastern orogenic Mountains in China. There occur various types of granitoids in China, such as calc-alkaline granite, alkali granite, highly-fractionated granite, leucogranite, adakite, and rapakivi granite. Rapakivi granites are not only typical Proterozoic as in the North China Craton, but were also emplaced during Paleozoic and Mesozoic in the Kunlun-Qinling orogen, a part of the China Central Orogenic Belt (CCOB). Nd-Hf isotopic tracing and mapping show that granitoids in the southern Central Asian Orogenic Belt (CAOB) in China (or the Northern China Orogenic Belt) are characterized predominantly by juvenile sources. The juvenile crust in this orogenic domain accounts for over 50% by area, distinguishing it from other orogenic belts in the world, and those in central (e.g., Qinling), southwestern and eastern China. Based on a large amount of new age data, a preliminary granitoid and granitoid-tectonic maps of China have been preliminarily compiled, and an evolutionary framework of Phanerozoic granitoids in China and neighboring areas has been established from the view of assembly and breakup of continental blocks. Research ideas on granitoid tectonics has also been proposed and discussed. 相似文献
16.
通过搜集显生宙以来不同地质时期内海相碳酸盐岩鲕粒及胶结物矿物成分、钾盐矿床矿物种类及组合特征、蒸发岩盆地中石盐流体包裹体成分,并利用这些资料与人工海水模拟实验得到的石盐中Br分配特征的对比,得出海水成分在5.5亿年以来的显生宙期间,经历了五个阶段:其中晚元古代至寒武纪早期、二叠纪早期至中生代早期、新生代早期至现今,这些时期的原始海水组成特征系数m(SO_4~(2-))+m(HCO_3~-)/2m(Ca~(2+)),为Na-Mg-K-SO_4-Cl型海水,此期间沉积的钾盐矿床的钾镁盐矿物主要为钾盐镁矾、无水钾镁矾、杂卤石、硫酸镁石等含MgSO_4矿物,海相鲕粒和碳酸盐胶结物矿物成分为文石;而寒武纪早期至石炭纪、中生代早期至新生代早期,原始海水组成特征系数m(Ca~(2+))m(SO_4~(2-))+m(HCO_3~-)/2,为Na-Mg-KCa-Cl型海水,此期间沉积的钾镁盐矿物主要为光卤石和钾石盐,甚至含有溢晶石,海相鲕粒和碳酸盐胶结物矿物成分为方解石。根据石盐流体包裹体成分计算得出:显生宙期间,海水K+含量大部分时间变化幅度较小,为9.3～11.5mmol/kg H_2O(除了石炭纪和晚元古代),平均为10.55mmol/kg H_2O。Mg~(2+)含量在早寒武世≥67mmol/kg H_2O、晚志留世至中泥盆世31～41mmol/kg H_2O、晚古生代≥48mmol/kg H22O、晚白垩世34mmol/kg H_2O和现代55.1mmol/kg H_2O。Ca~+含量在晚元古代至古生代早期≤11mmol/kg H_2O、古生代早期至石炭纪22～35mmol/kg H_2O、石炭纪至中生代早期≤17mmol/kg H_2O、中生代早期至新生代早期19～39mmol/kg H_2O及新生代早期至今7～21mmol/kg H_2O。SO_4~(2-)含量在晚元古代至古生代早期≥23mmol/kg H_2O、古生代早期至石炭纪5～17mmol/kg H_2O、石炭纪至中生代早期13～22mmol/kg H_2O、中生代早期至新生代早期5～19mmol/kg H_2O及新生代早期至今12～29.2mmol/kg H_2O。海水Ca~(2+)与SO_4~(2-)含量的相对变化是控制海相钾盐矿床钾镁盐矿物类型的基本因素。同时,利用以上数据计算得到的显生宙各时期海水[m(Mg~(2+))+m(SO_4~(2-))]/[m(K~+)+m(Ca~(2+))]的变化与各时期海相蒸发岩系石盐层底部的Br含量变化具有同步性,进一步验证了显生宙期间海水成分是不断变化的,是约束海相蒸发岩钾盐矿物类型的主要因素。海水成分变化的控制因素为洋中脊热液和陆地水,其中洋中脊热液起主要作用,而控制这些因素变化的根本原因为板块构造运动。 相似文献
17.
西藏冈底斯山中段第四纪火山岩特征及地质意义 总被引：7，自引：1，他引：7
为辨别环境动态变化而进行的多期次环境地球化学填图要求降低不同期次数据间的分析误差，为达此目的，本文提出了衡量各实验室分析质量的新的考核标准，包括：一组标准样不同元素分析值与标准值对数偏差的不合格率；一组标准样不同元素分析值与标准值的相关系数所反映的相似性系数；一组标准样各种元素分析值与标准值在虚拟空间上图形分布的相似性。 相似文献
18.
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鄱阳盆地的前白垩系基底岩系因区域构造位置而异,长山隆起为元古界变质岩,北鄱阳坳陷为呈冲断岩片展布的震旦系志留系,南鄱阳坳陷主体部位为呈冲断结构的石炭系侏罗系,南冲的前峰带因剥蚀严重而出现双桥山群变质岩系。盆地的前白垩纪基底是一个在燕山运动时再度活化的印支期陆内造山带,因而构造线方向与印支期陆内造山带的走向相同(总体呈北东东向),冲断的方向则由燕山期的造山极性控制(自北西向南东),冲断活动发生在晚侏罗世和早白垩世早期。 相似文献
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关于蓟县型中、上元古界沉积环境及内蒙地轴的性质 总被引：7，自引：0，他引：7
内蒙地轴和燕辽坳都是华北地台北缘的二级大地构单元,本文在对蓟县型中、上元古界沉积环境和对内蒙地轴演化历史的初步研究基础上,认为蓟县型中、上元古界沉积盆地于长城－蓟县期,在北部与广海相连,属于陆表海发展,在青白口期,由于北部逐渐抬升,该沉积盆地才具有陆内盆地性质,内蒙地轴在长城－蓟县期总体处于水下环境,青白口爰开始抬升为古陆,其大规模抬升可能是在古生代或更晚。 相似文献