中国西北地区早—中侏罗世盆地原型分布   总被引：3，自引：0，他引：3  

张贵宾 《地学前缘》2000,7(4)

文中进行了中国西北地区早—中侏罗世盆地的原型分析,着重阐述3点：(1)根据盆地构造特征,将中国西北地区早—中侏罗世盆地划分为：缓断面伸展断陷盆地、陡断面伸展断陷盆地、克拉通内盆地和克拉通周边盆地4种类型。(2)这4类盆地分布于不同的前侏罗纪构造背景之上。第Ⅰ类和第Ⅱ类伸展断陷盆地位于印支晚期造山带和印支晚期复活的古生代造山带,它们系造山带伸展垮塌作用的产物。第Ⅲ类克拉通内盆地分布于克拉通块体内部,它们具有冷的刚性岩石圈,其古地温梯度达不到使岩石圈弱化和产生伸展断陷盆地的临界值。第Ⅳ类克拉通周边盆地位于克拉通和造山褶皱带之间,这类盆地的古地温梯度刚达到形成伸展断陷盆地临界值,在应变速率低的情况下造成不对称的宽阔凹陷。(3)由于这4类盆地的地温梯度、演化和改造程度不同,它们的含油气远景差别很大,其中以克拉通周边盆地最有希望。  相似文献   

早前寒武纪地质及深成构造作用研究进展   总被引：4，自引：0，他引：4  

李江海 《高校地质学报》1998,4(3):303-312

早前寒武纪地质的研究进展主要表现在准大陆克拉通早期构造演化,克拉通及古老造山带深层结构,元古代超大陆恢复对比、早期地壳性质及生长等主要问题上开展多学科研究计划的实施。其中,同位素年代学,特别是锆石Ｕ－Ｐｂ方法,地震反射、Ｐ－Ｔ计算及古地磁研究对前寒武纪地质学的进展具有重要的推动作用。和个古陆克拉通区域地质学的持质研究积累,不断产生新的认识,这种新的科学思想涉及到早期陆壳组成及区划,太古代克拉通化历史,太古代－元古代界限及性质,元古代造山带网络与克拉进陆块拼合,大陆下地壳剖面及其组成等同题。华北早前寒武纪地质演化研究中的重要问题包括：华北麻粒岩相带与克拉通基底构造的关系,克拉通基底构造区域,早期陆壳性质及其记录的重大构造一热事件幕,华北克拉通与世界典型陆块构造演化对比等。  相似文献   

塔里木克拉通形成以来的背景热史研究          下载免费PDF全文

曹厚臻  何丽娟  张林友 《地球物理学报》2019,62(1):236-247

塔里木盆地是一个典型大型叠合盆地,发育在太古代-早中元古代的结晶基底之上,具有稳定克拉通性质.现今地表热流为43mW·m^-2,平均地温梯度为21℃·km-1,莫霍面温度为550℃,较低的热流背景值指示塔里木盆地经历了一个长期冷却加厚的过程.然而对于这样一个长期冷却过程,之前的研究都只停留在显生宙阶段,并未获得塔里木显生宙以前的热史.本文以塔里木地区已有的地热数据作为约束,依据地幔动力学模型设置底部边界条件,利用正演拟合的方法,反演出塔里木的背景热史,填补了该区域古生代以前热史研究的空白.结果表明,塔里木克拉通自形成以来背景热流不断降低(由85mW·m^-2降至43mW·m^-2),岩石圈持续加厚(由130km加厚到190km),在长时间尺度下,塔里木克拉通总体的热演化模式为长期冷却加厚,这与世界上其他典型克拉通的热演化规律类似.显生宙以来受到短期局部的构造-热事件影响,塔里木克拉通在长期冷却的趋势下叠加了约20～40mW·m^-2的热扰动.  相似文献   

基于P波三重震相的华南地区上地幔速度结构研究   总被引：2，自引：1，他引：1       下载免费PDF全文

吕苗苗  丁志峰  朱露培 《地球物理学报》2017,60(10):3765-3779

华南块体是研究太平洋板块俯冲和岩石圈减薄机制等问题的最佳场所之一.本文基于中国地震观测台网和大型流动台阵记录到的震中距10°~30°之间的两个中深源地震P波记录,利用三重震相波形拟合技术,获得了中扬子克拉通和华夏地块上地幔高精度P波速度结构.研究结果表明:(1)中扬子克拉通过渡带底部存在高速异常,系太平洋俯冲板块的滞留体.俯冲的板块并没有进入下地幔,660-km间断面下沉约11 km,与后尖晶石相变的克拉伯龙斜率为负有关.而华夏地块过渡带底部并无明显高速异常,接近全球平均模型;(2)整个华南块体,410-km间断面上方普遍存在低速层,主要与上地幔部分熔融有关,与IASP91相比P波速度减小了1.38%~2.29%;(3)在研究区域内,中扬子克拉通和华夏地块都存在岩石圈减薄(80 km),推测可能与太平洋板块俯冲和快速回撤导致的岩石圈拆沉有关.且华夏地块减薄程度较明显,下伏软流圈速度较低,说明其上地幔强度较弱、温度较高.另外,中扬子克拉通过渡带中存在一个较宽的速度梯度带,可能与520-km间断面有关,其具体成因有待进一步研究.  相似文献   

Zircon U–Pb and Lu–Hf systematics of the major terranes of the Western Superior Craton,Canada: Mantle-crust interaction and mechanism(s) of craton formation     

《Gondwana Research》2020

Paleo-to Neoarchean granitoid gneisses (ca. 3.30 to 2.49 Ga) are well preserved in the Western Superior Craton. Protoliths of these gneisses are mainly I-type granitoids characterized by high Sr/Y and La/Yb ratios and low Mg#, consistent with Archean tonalite-trondhjemite-granodiorites. Zircons from granitoid gneisses commonly contain three growth phases: inherited cores (zircon I), magmatic rims (zircon II) and outer rims that have undergone Pb-loss (zircon III). The 3.12 Ga to 2.86 Ga zircon I represent early crustal material, that was captured in younger zircons; zircon II preserve crustal re-working and younger crustal additions that are constrained between 2.85 to 2.72 and 2.69 to 2.65 Ga.Zircon II contains both positive and negative εHf(t) values (−6.3 to +8.1), with both depleted-mantle and older crustal signatures. Half of the magmatic rims (II) are characterized by depleted mantle signatures with positive εHf(t) values representing juvenile crust-forming events, whereas the other half are characterized by recycled crustal signatures with negative εHf(t) values. εHf(t) results show that the North Caribou and the Island Lake terranes and the northern Uchi domain are isotopically more enriched than the southern Uchi, English River, Wabigoon and Winnipeg River terranes, suggesting the northern Uchi margin represents a major terrane boundary.Based on mass balance calculations, large volumes of juvenile material at circa 3.0 Ga mixed with smaller amounts of older crust. The vast majority of the granites were derived from a source with about 50% mantle material during the peak crust formation events after 2.8 Ga. The decline in the volume of felsic magmatism in the later Archean is coeval with a reduced supply of both heat and material from depleted mantle sources. Combined with previously published geochemical, geochronological and isotopic data, this suggests an evolution in felsic magma sources consistent with crustal thickening.  相似文献   

P-T path of metamorphism and U-Pb monazite and zircon age of the Kitoy terrane: Implication for Neoarchean collision in SW Siberian Craton     

《地学前缘(英文版)》2020,11(6):1915-1934

The first data on P-T metamorphic conditions coupled with U-Pb monazite and zircon age obtained for the Neoarchean Kitoy granulite-gneiss terrane (SW Siberian Craton). Alumina gneisses of the Kitoy terrane indicate two-staged metamorphic evolution. The first stage of regional metamorphism (M1) occurred at high-amphibolite facies conditions at T ​= ​780–800 ​°C and P ​= ​8–9 ​kbar. The second stage (M2) belongs to MT-HT/LP type of metamorphism with the wide temperature interval 600–750 ​°C and pressure 2–4 ​kbar. Two age peaks were established on the basis of U-Pb monazite and zircon dating in garnet-anthophyllite gneisses. Both of them correspond to the Neoarchean age: the age of M1 falls into the interval of ca. 2489–2496 ​Ma, the age of M2 – ca. 2446–2456 ​Ma. The high-temperature metamorphism of the Kitoy block and nearly coeval granitoid magmatism can be an evidence for the Neoarchean collision in SW Siberian craton.  相似文献   

碧口群火山岩岩石成因研究   总被引：13，自引：1，他引：12  

夏林圻  夏祖春  徐学义  李向民  马中平 《地学前缘》2007,14(3):84-101

新元古代(846~776Ma)碧口群火山岩喷发于大陆板内裂谷环境。该火山岩系以基性火山岩为主,酸性火山岩次之,中性火山岩少见。根据岩石地球化学数据,碧口群裂谷基性熔岩总体上属于低Ti/Y(<500)岩浆类型。元素和同位素数据表明,碧口群基性熔岩的化学变化不是由一个共同的母岩浆的结晶分异作用所产生。它们极有可能是源于地幔柱源(εNd(t)≈+3,87Sr/86Sr(t)≈0.704,La/Nb≈0.7)。地壳混染作用对于碧口群裂谷基性熔岩的形成有重要贡献。我们的研究揭示,碧口群火山岩存在空间上的岩石地球化学变化。东部红岩沟和辛田坝—黑木林地区的碧口群基性熔岩以拉斑玄武岩为主,产生于幔源石榴子石稳定区的高度部分熔融。相反,西部白杨—碧口地区的碧口群基性熔岩的母岩浆则是形成于幔源的尖晶石-石榴子石过渡带:碱性熔岩是产生于部分熔融程度较低的条件下,拉斑玄武质熔岩则是产生于部分熔融条件较高的条件下。它们经受了浅层位辉长岩质(cpx+plag±ol)分离作用,化学变异较大。  相似文献   

Frequency ratio modelling using geospatial data to predict Kimberlite Clan of rock emplacement zones in Dharwar Craton,India     

《International Journal of Applied Earth Observation and Geoinformation》2019

Kimberlite clan of rocks (KCR) comprising of mantle derived ultrabasic rocks such as Kimberlite and related Lamproites and Lamprophyres,are the primary source of diamond. Locating the KCR is first step in the diamond exploration, which is highly challenging in the field due to (i) very small spatial extent of KCR pipes (ii) high susceptibility of KCR to weathering and alteration on exposure to atmosphere, owing to their ultrabasic composition. Predictive statistical models using the geospatial data are often used to minimize the search and the present work attempts to apply the Frequency Ratio (FR) based predictive model in GIS to prepare KCR potential zone maps based on the relationship between the already explored KCR locations and the factors that favour their emplacement. Wajrakarur Kimberlite Field (WKF) in the Dharawar Craton of India, with more than 30 explored kimberlite pipes is selected as the study area. Geospatial technology has been used to generate thematic maps such as known KCR pipe locations, lineament density, lineament buffer zone, lineament intersection buffer zone, drainage anomaly buffer zone, geomorphology, and classified image showing distribution of mineral such as clay, iron oxide and calcrete, which are surface expression of KCR emplacement from various sources. Landsat 8 OLI satellite data, ASTER DEM were used in preparing the geomorphology, lineament map, and band ratio based mineral classified map. The thematic maps were converted to raster grid of 10 sq. m. FR values for each unit in each thematic map were obtained by correlating the spatial relationship between thematic map and the 25 locations of the 33 “known” KCR locations in WKF used for FR modelling. Cumulative FR value were obtained by carrying out overlay analysis of the thematic maps, which are classified into five classes by Natural Breaking method as (i)Very Low Favourable (VLF), (ii) Low Favourable (LF), (iii)Moderate favourable (MF), (iv)High Favourable (HF), and (v)Very High Favourable (VHF). The model was validated by ground verification at random sites and statistical method. During the ground visit, we observed KCR-like lithology’s at four new sites that have calcrete exposure at limited spatial extent and also some pieces of ultrabasic rocks similar to the explored sites. To ascertain their chemical composition of the samples were plotted in the MgO-K₂O-Al₂O₃ ternary diagram. All the four samples fall in the Kimberlite/Lamproite field confirming them to be KCR. The FR predictive model was also validated statistically. Total 13 locations, including 8 site out of 33 known KCR locations, one newly discovered pipe by GSI and the four locations discovered during this study were used for the validation. Statistical validation shows that 84% of model accuracy is achieved. The study reveals that Lineament Intersection, and circular drainage anomaly in 3rd order streams, lineament density are significant themes in predicting KCR emplacement zones. The study demonstrates the utility of statistical based model such as FR model in predicting the location of KCR emplacement, even with statistically insignificant distribution of KCRs and can be applied elsewhere in the world to locate the KCRs. In the process, we report discovery of four new KCR pipes in the WKF.  相似文献   

大陆动力学数值模拟:问题、进展与展望     

李忠海  崔起华  钟辛易  刘明启  王杨  皇甫鹏鹏 《地质学报》2021,95(1):238-258

大陆动力学是地球动力学的基本组成部分,是板块构造理论的重要拓展,是固体地球科学的核心命题之一.在系统的地质、地球物理和地球化学观测的基础上,数值模拟是探讨大陆动力学过程和机制的有效手段.本文主要基于大陆动力学数值模拟,围绕大陆形成和演化过程的四个关键科学问题进行总结和探讨.①大陆起源与早期地球动力学演化.现今观测到的最...  相似文献