苏鲁高压-超高压带的结构、变形特征及形成背景探讨   总被引：1，自引：0，他引：1  

张忠义  吴淦国  宋明春  张达 《地球学报》2004,25(6):607-614

苏鲁高压-超高压变质带由不同层次、不同级别、不同变质岩石组合的构造岩片堆叠而成,自北向南可分别为9个构造岩片。这种复杂的结构的形成和发展主要受早期的变质变形作用控制,并被晚期构造作用改造。本文重点对高压-超高压变质带的构造变形进行了分析,自元古宙—中生代韧性改造事件可分为4期。最后在以上工作的基础上对其形成的地质背景进行了探讨,指出了两次高压-超高压变质事件存在的可能,而且其新元古代的构造事件可与全球Rodinian超大陆的形成与裂解相对比。  相似文献   

东昆仑南带中元古代晚期-新元古代早期叠层石组合的发现          下载免费PDF全文

边千韬  朱士兴  I. I. Pospelov  M.A. Semikhatov  孙淑芬  陈代钊  那春光 《地质科学》2006,41(3):500-510

东昆仑南带加嗡门地区碳酸盐岩地层中发现的中元古代晚期-新元古代早期叠层石组合以大型锥叠层石及其相关的分子Conophyton garganicus var. inkeni,C. cf. ressoti Menchikov, Jacutophyton f. 和Conicodomenia cf. longotenuia等最丰富, 并与Baicalia共生, 故可视之为Conophyton-Baicalia组合.这叠层石组合可以与天山、华北等地蓟县系中部-青白口系中部叠层石组合对比,尤其酷似于天山地区蓟县系的爱尔基干组合和华北蓟县系的闪坡岭叠层石组合,而显著有别于华南地块.它还可以与南乌拉尔、西伯利亚、北美、北非和阿拉斯加半岛等地区的中里菲界上部--上里菲界下部层位中的叠层石组合对比.加嗡门叠层石组合的时限为距今1 300～850 Ma,大致为蓟县纪中期-青白口纪中期或中里菲晚期-晚里菲早期.东昆仑南带存在前寒武纪微地块,当时此微地块的古地理和古环境与天山、华北、西伯利亚和阿拉斯加半岛等地区的前寒武纪地块相似,均位于低纬度区,其上均广泛发育适宜叠层石繁育的温暖陆表海,它们可能共同处于罗迪尼亚超大陆的低纬度大陆边缘部位,与华南地块的不同.这对本区和东昆仑地层和大地构造研究,以及对罗迪尼亚超大陆重建提供了新的古生物约束.  相似文献   

中祁连苏里地区新元古代辉绿岩墙群LA-ICP-MS锆石U-Pb年龄及其地质意义     

张金明  才航加  陈光庭  田成秀  雷晓清 《岩石矿物学杂志》2020,39(6):769-779

中祁连西段苏里地区有大量北东和近东西向延伸的辉绿岩、辉长岩呈岩墙状侵入到元古宙地质体中。基性岩墙的SiO₂含量为46.77%～52.37%,Al₂O₃含量为12.82%～15.86%,TiO₂含量为1.16%～3.14%,MgO含量为3.84%～7.98%,FeO^T含量为10.42%～15.53%,以贫K₂O （0.10%～1.60%）、Na₂O>K₂O为特征,里特曼指数σ=0.67～2.96,岩石主量元素地球化学成分与大洋拉斑玄武岩一致;全岩稀土元素总量较低（51.28×10^-6～165.11×10^-6）,轻重稀土元素之比为2.67～4.90,（La/Yb）_N值为2.04～5.03,属轻稀土元素富集型,δEu=0.93～1.12,无明显的Eu异常;富集Rb、Ba、Th、U,亏损Nb和K,大离子亲石元素丰度变化范围相对较宽,高场强元素富集程度不强,微量元素蛛网图上具有左侧隆起、右侧相对平坦的分布型式。基性岩墙LA-ICP-MS锆石U-Pb年龄为819.5±5.2 Ma,形成时代与全球性Rodinia超级大陆裂解时代高度一致。岩石地球化学分析结果显示岩浆起源于亏损地幔源区,是尖晶石地幔橄榄岩部分熔融的产物,岩浆形成于陆内裂谷环境,表明其可能为Rodinia超级大陆裂解的产物。  相似文献   

Decoding earth's plate tectonic history using sparse geochemical data     

Michael G.Tetley  Zheng-Xiang Li  Kara J.Matthews  Simon E.Williams  R.Dietmar Müller 《地学前缘(英文版)》2020,11(1):265-276

Accurately mapping plate boundary types and locations through time is essential for understanding the evolution of the plate-mantle system and the exchange of material between the solid Earth and surface environments.However,the complexity of the Earth system and the cryptic nature of the geological record make it difficult to discriminate tectonic environments through deep time.Here we present a new method for identifying tectonic paleo-environments on Earth through a data mining approach using global geochemical data.We first fingerprint a variety of present-day tectonic environments utilising up to 136 geochemical data attributes in any available combination.A total of 38301 geochemical analyses from basalts aged from 5-0 Ma together with a well-established plate reconstruction model are used to construct a suite of discriminatory models for the first order tectonic environments of subduction and mid-ocean ridge as distinct from intraplate hotspot oceanic environments,identifying 41,35,and 39 key discriminatory geochemical attributes,respectively.After training and validation,our model is applied to a global geochemical database of 1547 basalt samples of unknown tectonic origin aged between 1000-410 Ma,a relatively ill-constrained period of Earth’s evolution following the breakup of the Rodinia supercontinent,producing 56 unique global tectonic environment predictions throughout the Neoproterozoic and Early Paleozoic.Predictions are used to discriminate between three alternative published Rodinia configuration models,identifying the model demonstrating the closest spatio-temporal consistency with the basalt record,and emphasizing the importance of integrating geochemical data into plate reconstructions.Our approach offers an extensible framework for constructing full-plate,deeptime reconstructions capable of assimilating a broad range of geochemical and geological observations,enabling next generation Earth system models.  相似文献   

云南安宁地区石虎山花岗岩年代学、地球化学特征和锆石Hf同位素组成及其成因          下载免费PDF全文

刘军平  孙柏东  崔晓庄  熊波  宋冬虎  白春东  张坤  杨仕潘 《中国地质》2020,47(3):693-708

石虎山花岗岩岩体位于安宁市德滋村附近,本文对该岩体开展了LA-ICP-MS锆石U-Pb定年、岩石地球化学、锆石Hf同位素组成研究。结果获得(616±20) Ma的岩浆结晶年龄和(839±17) Ma、(766±15) Ma、(705.5±9.4) Ma的继承性年龄,说明岩体形成于新元古代埃迪卡拉纪;其中(839±17) Ma、(766±15) Ma、(705.5±9.4) Ma的继承性年龄组合可能是Rodinia超大陆裂解构造过程的记录,839 Ma、616 Ma可能是Rodinia超大陆在扬子板块西缘开始裂解与最终裂解时限。花岗岩主量、微量元素特征显示,其产生于伸展环境的高硅、过铝、高钾的A型花岗岩;锆石ε_(Hf)(t)值均小于0,在t-t(Ma)和t-(~(176)Hf/~(177)Hf)图上,所有样品点均落在上地壳演化线之上,二阶段模式年龄变化范围为1.77～2.31 Ga,结合Nb/Y—Rb/Y图解,表明成岩物质主要来源于古元古代古老下地壳页岩60%部分熔融。  相似文献   

川东北新元古代克拉通裂陷的厘定及其深层油气意义          下载免费PDF全文

汪正江  汪泽成  余谦  彭军  杜秋定 《沉积与特提斯地质》2021,41(3):361-375

四川盆地安岳震旦—寒武系特大型气田的发现,极大地鼓舞了相关学者对四川盆地深层油气勘探新领域的探索热情,然而,对于川东北地区深层古地理格局的认识尚存在不少争议.本文通过对四川盆地北缘、东北缘新元古代—寒武纪地层剖面的综合调查与区域对比研究,基于关键事件序列的系统厘定,重建了川东北及邻区的新元古代—寒武纪原型盆地地层格架;...  相似文献   

Two Neoarchean supercontinents? Evidence from the Paleoproterozoic   总被引：10，自引：0，他引：10  

Lawrence B. Aspler  Jeffrey R. Chiarenzelli 《Sedimentary Geology》1998,120(1-4):75-104

An unresolved question in Precambrian geology is the relationship between Archean crustal fragments that are now separated by younger orogens: were they once contiguous? Williams et al. (1991) proposed the name ‘Kenorland' for a speculative Neoarchean supercontinent comprising the Archean provinces in North America. Recently, a large number of ca. 2.5–2.0 Ga magmatic, metamorphic, detrital and xenocrystic ages have been reported from North America. We interpret that the wide geographic distribution and temporal spread of these ages may signify long-lived, regional-scale mantle upwelling, and anorogenic magmatic and metamorphic processes related to the protracted breakup of Kenorland. Breakup may have extended from ca. 2.5 to 2.1 Ga, culminating with dispersion of continental fragments at ca. 2.1–2.0 Ga. In North America, ca. 2.5–2.1 Ga intracratonic basin successions (e.g. Hurwitz Group) formed in the interior of Kenorland before dispersion, and passive margin sequences flanking the Superior Province (e.g. Huronian Supergroup) and the Wyoming Province (e.g. Snowy Pass Supergroup) defined the edges of Kenorland. Earliest Paleoproterozoic magmatic and sedimentary rocks, which include voluminous quartz arenites and glacigenic deposits, are consistent with a high-standing supercontinent and a mantle superplume. The Paleoproterozoic record from the Baltic and Siberian shields is similar to that of North America, suggesting inclusion in Kenorland. A slightly different record from the southern continents suggests a second, coexisting supercontinent that included the Zimbabwe, Kaapvaal, and Pilbara cratons, (‘Zimvaalbara' of I.G. Stanistreet), the São Francisco Craton, and possibly, cratonic blocks in India. Attenuation of this second supercontinent started earlier than in Kenorland (ca. 2.65 Ga) and was accompanied by high sea level and deposition of vast Lake Superior-type iron formations. Immediately thereafter, both supercontinents became emergent and were subject to global cooling and glaciation.  相似文献   

锆石U-Pb年龄及Lu-Hf模式年龄对印支地块基底的限定          下载免费PDF全文

王超  王世锋  莫亚思 《地质科学》2016,(2):576-593

印支地块的板块构造归属不仅对特提斯演化研究有重要意义, 对探讨新生代青藏高原及周缘板块的陆内变形同样至关重要.我们近期的研究工作表明, 本区的花岗岩主要是印支期旧特提斯闭合的产物, 少数花岗岩与加里东期的构造活动有关.花岗岩内锆石Lu-Hf二阶段模式年龄主要聚集在1.8~1.6 Ga, 此外在1.4~1.2 Ga有另一峰值区.老挝北部花岗岩峰值区与印支地块内其它地区的锆石U-Pb年龄及Lu-Hf二阶段模式年龄峰值相似, 表明印支地块内部有稳定的基底组成.老挝花岗岩年龄峰值与昌都-思茅地块的年龄峰值近于一致, 同时, 由于奠边府构造带不具有缝合带的属性且两个地块有相似的古生代暖水动物群, 我们认为印支地块与昌都-思茅地块可能为同一陆块, 这个联合陆块与华南陆块在Rodinia超大陆时期可能是一体的, 因为他们的峰值区在4.0~3.5 Ga, 2.0~1.8 Ga, 1.4~1.2 Ga的3个峰值区完全重合.  相似文献   

湘西北花垣县下寒武统清虚洞组浊积岩沉积特征及其地质意义   总被引：5，自引：0，他引：5       下载免费PDF全文

匡文龙  杨绍祥  余沛然  劳可通 《地质科学》2008,43(2):347-358

湘西北花垣县及邻区,在下寒武统清虚洞组下部发育一套地质特征典型、沉积序列明显的浊积岩。其底面侵蚀构造清楚,覆盖于底面上的各层段厚度变化较大,在各层段内由下往上碎屑粒度依次变细,并相继出现有变形纹层、平行纹层和波痕纹层理等沉积构造,是典型的浅海浊积岩。据各层段的发育情况可总结为5种剖面结构。因冰川消融而使海平面上升,故清水洞组浊积期海水深度增大。浊流活动受北东东向保靖—花垣断裂控制,其活动与新元古代发生并延续到早古生代的罗迪尼亚超大陆裂解事件有关。  相似文献   

浙闽地区新元古代变火山岩系岩石地球化学特征及其地质意义   总被引：3，自引：0，他引：3  

靳松  张利  钟增球  周汉文  向华  曾雯  刘锐 《矿物岩石》2008,28(1):97-105

浙闽地区华夏地块前寒武纪上基底主要由出露于阈西北和浙西南的马面山群、万全群和龙泉群组成.对比研究表明,以上3个岩群具有相似的构造演化、岩石组合、元素地球化学特征及形成时代,它们共同组成了统一的华夏地块变质上基底,在构造上是相连的,主要由经历了高绿片岩相-低绿帘角闪岩相变质变形作用的绿片岩和变粒岩组成,其原岩为一套双峰式火山岩,形成于新元古代中期.绿片岩的稀土配分型式右倾,轻重稀土分异较大,具洋岛玄武岩(OIB)的特征,其微量元素表现为左部"大隆起"式的特征,大离子素石元素(LILE)K,Rb,Ba,Th明显富集,Nb相对La富集,表现出大陆裂谷玄武岩的特征.绿片岩和变粒岩具有统一的岩浆演化趋势,为同源岩浆演化的产物,地球化学特征和构造判别图解显示它们形成于板内拉张的大陆裂谷环境,可能是新元古代Rodinia泛大陆裂解在华南的记录,与地幔柱的活动有关.马面山群第二类绿片岩表现出岛弧特征,可能为陆壳物质混染所致.  相似文献