内蒙古那仁乌拉早白垩世高分异花岗岩年代学及其成因     

李柱  张德会  张荣臻  沈存利  焦世豪  李林  朱鹏龙 《现代地质》2022,36(3):848-861

内蒙古那仁乌拉地区具有较大的稀有金属找矿潜力,但与成矿有关的那仁乌拉花岗岩体在年代学和成因方面仍存在较多争论。为厘定该花岗岩体成岩年龄及成因类型,对其进行了LA-ICP-MS锆石U-Pb定年和岩石地球化学分析。测年结果表明,中粗粒黑云母二长花岗岩和似斑状二长花岗岩成岩年龄分别为(142.1±1.0)Ma和(142.3±1.2)Ma,指示那仁乌拉花岗岩体为早白垩世岩浆活动的产物,与区域上晚侏罗世—早白垩世花岗岩大规模侵入时代基本吻合。岩石地球化学分析显示,岩体富硅(SiO₂含量为73.69%~76.67%)、富碱(Na₂O+K₂O含量为8.40%~8.80%)和贫铁、镁、钙、磷等;Zr、Hf、Rb、Th等元素明显富集,Ba、Sr、P、Ti等元素强烈亏损,Nb元素相对亏损;稀土元素总量较低,显示较强烈的Eu负异常(δEu=0.20~0.36),轻、重稀土分馏明显(LREE/HREE=6.23~14.28),富集轻稀土;属于弱过铝质高钾钙碱性花岗岩。综合矿物学、岩石学和地球化学特征,判断那仁乌拉花岗岩成因类型应归为高分异I型花岗岩。结合区域构造和地质背景,认为位于华北板块北缘的那仁乌拉花岗岩体形成于早白垩世的板内伸展环境。  相似文献   

准噶尔盆地莫西庄—永进地区白垩系清水河组地貌演化及沉积响应     

朱珍君  李琦  李剑  陈贺贺  胡俊杰  耿慧  丁晓军  白金莲 《现代地质》2022,36(1):105-117

不同古地貌背景下,盆地沉积充填特征不同。以准噶尔盆地莫西庄—永进地区白垩系清水河组为例,综合野外露头、岩心、测井、分析化验和三维地震资料,进行古地貌演化背景下白垩系清水河组层序地层、沉积物源和沉积体系研究。研究结果表明:莫西庄—永进地区白垩系清水河组发育一个完整的三级层序,清水河组一段发育低位体系域(LST)和湖侵体系域(TST),清水河组二段发育高位体系域(HST)。早白垩世,车排子—莫索湾古隆起(车—莫古隆起)整体埋藏,古隆起局部高部位仍出露地表,随着盆地全区接受稳定沉积,古隆起逐渐消亡。LST时期,盆地沉积中心位于研究区北部;TST至HST时期,在北部构造抬升掀斜作用下,盆地地形趋于平缓,沉积中心逐渐南迁。在此构造演化背景下,盆外北部物源体系由东北、西北方向向研究区供源,在盆地缓坡带浅水背景下发育远源辫状河三角洲—滨浅湖沉积体系。LST时期,受古隆起残余地貌、湖平面变化及水动力条件的共同影响,沉积碎屑多沉积于地貌低势区,发育局限展布的浅水辫状河三角洲,研究区以三角洲内前缘沉积为主,水下分流河道连片发育;LST时期发育的沉积体系平缓了原始地貌,在车—莫古隆起上继承性沉积TST时期的滨浅湖沉积体系和HST时期的浅水辫状河三角洲沉积体系,其中HST时期研究区以三角洲外前缘沉积为主,广泛发育席状砂,局部发育水下分流河道。继承性地貌控制盆地不同部位的沉积可容空间,决定沉积物搬运及分散路径,进而控制盆地的沉积充填类型和特征。  相似文献   

Crust–mantle interaction recorded by Early Cretaceous volcanic rocks within the southern margin of the North China Craton     

《地学前缘(英文版)》2022,13(6):101447

This study presents new geochronological and geochemical data for Early Cretaceous volcanic rocks in the southern margin of the North China Craton (NCC), to discuss the crust–mantle interaction. The studied rocks include pyroxene andesites from Daying Formation, hornblende andesites and andesites from Jiudian Formation, and rhyolites from a hitherto unnamed Formation. These rocks formed in Early Cretaceous (138–120 Ma), with enrichment in light rare earth elements (REE), depletion in heavy REE and arc-like trace elements characteristics. Pyroxene andesites show low SiO₂ contents and enriched Sr–Nd–Pb–Hf isotopic compositions, with orthopyroxene phenocryst and Paleoproterozoic (2320–1829 Ma) inherited zircons, suggesting that they originated from lithospheric mantle after metasomatism with NCC lower crustal materials. Hornblende andesites have low SiO₂ contents and high Mg# (Mg# = 100 Mg/(Mg + Fe²⁺)) values, indicating a lithospheric-mantle origin. Considering the distinct whole-rock Sr isotopic compositions we divide them into two groups. Among them, the low (⁸⁷Sr/⁸⁶Sr)_i andesites possess amount inherited Neoarchean to Neoproterozoic (2548–845 Ma) zircons, indicating the origin of lithospheric mantle with addition of Yangtze Craton (YC) and NCC materials. In comparison, the high (⁸⁷Sr/⁸⁶Sr)_i andesites, with abundant Neoarchean–Paleozoic inherited zircons (3499–261 Ma), are formed by partial melting of lithospheric mantle with incorporation of NCC supracrustal rocks and YC materials. Rhyolites have extremely high SiO₂ (77.63–82.52 wt.%) and low total Fe₂O₃, Cr, Ni contents and Mg# values, combined with ancient inherited zircon ages (2316 and 2251 Ma), suggesting an origin of NCC lower continental crust. Considering the presence of resorption texture of quartz phenocryst, we propose a petrogenetic model of ‘crystal mushes’ for rhyolites prior to their eruption. These constraints record the intense crust–mantle interaction in the southern margin of the NCC. Given the regional data and spatial distribution of Early Cretaceous rocks within NCC, we believe that the formation of these rocks is related to the contemporaneous far-field effect of the Paleo-Pacific Plate.  相似文献   

西藏那曲地区早白垩世A型花岗岩成因及其构造意义     

李金勇  翟庆国  唐跃  胡培远  王伟  刘一鸣  杨宁 《地质学报》2023,97(5):1418-1433

班公湖-怒江缝合带及其两侧广泛分布早白垩世岩浆岩,它们是班公湖-怒江洋俯冲消减及拉萨地块与南羌塘地块碰撞过程的直接响应,为研究特提斯大洋演化、青藏高原早期陆块聚合提供了重要素材。本文报道了班公湖-怒江缝合带中段那曲地区黑云母二长花岗岩的锆石U-Pb定年、岩石地球化学和锆石Hf同位素分析结果。锆石LA-ICP-MS U-Pb定年结果表明,黑云母二长花岗岩形成于114～113 Ma(早白垩世晚期)。地球化学分析表明,岩石显示出高钾钙碱性—钾玄岩系列特征,同时具有高的Ga/Al×10000比值(介于2.02～3.15之间,平均为2.61)和Zr+Nb+Ce+Y含量(平均为524.87×10^-6)。此外,锆饱和温度和锆石Ti温度计共同指示岩浆形成于高温的环境(>800℃),这些特征与典型的A型花岗岩相一致。黑云母二长花岗岩中锆石具有低的ε_Hf(t)值(10.1～6.4),对应的Hf同位素二阶段模式年龄(t_DM2)为1852～1547 Ma,指示其岩浆可能源自安多微陆块中下地壳古老结晶基底的部分熔融。结合区域研究成果,认为那...  相似文献   

印尼西婆罗洲早白垩世Mensibau花岗岩类的成因及构造意义     

郭东海  刘铁翊  朱俊宾  姜冠哲  李舢 《地质论评》2023,69(4):1249-1268

婆罗洲西部(印尼)在中生代期间处于特提斯构造域和古太平洋构造域交汇地带,是全球少有的多重板块动力学体制既有先后叠加又有同时复合的独特大地构造单元。因此,该区相关花岗岩类成因及构造背景的研究对揭示东南亚构造—岩浆演化历史及多重构造体制叠合造山作用下的岩浆演化机制至关重要。笔者等对西婆罗洲Mensibau岩基的花岗岩类进行了锆石U-Pb年代学、元素地球化学和Sr-Nd-Hf同位素分析。其中,石英二长岩和钾长花岗岩样品的LA-ICP-MS锆石U-Pb同位素年龄分别为126.9±2.1 Ma和141.8±2.6 Ma,表明岩体形成于早白垩世,岩浆活动至少持续了15 Ma。Mensibau花岗岩类具有高SiO₂(67.5%～73.3%)、高K₂O (4.3%～5.4%)和低P₂O₅(0.07%～0.14%)的元素含量特征,铝饱和指数(A/CNK)为0.92～1.06,并且含角闪石,属准铝质—弱过铝质I型花岗岩类。这些花岗岩类具有轻稀土元素(LREEs)富集和重稀土元素(HREEs)亏损,弱的负铕异常(δEu=...  相似文献   

Grading Evaluation and Ranking of CO₂ Sequestration Capacity in Place(CSCIP) in China's Major Oil Basins: Theoretical,Effective, Practical and CCUS-EOR     

LI Yaohu  WANG Yang  SHI Yu  YANG Leilei  CUI Qiliang  BI Caiqin  XU Yinbo  WANG Qianyou  SHAN Yansheng  LIU Weibin  MIAO Miao  WANG Ting 《《地质学报》英文版》2023,97(3):873-888

Because it is necessary to focus on differences in regional oil reservoirs and determine the priority of the CCUSEOR(Carbon capture, utilization, and storage-enhanced oil recovery) deployment under China’s net-zero CO₂ emission target, systematic and regional evaluations of CO₂ sequestration capacity in major oil basins are needed considering the geofluid properties―carbon sequestration capacity in place(CSCIP)―where the ’in place’ indicates actual geological formation cond...  相似文献   

Lithospheric thinning and ignition of a Cordilleran magmatic flare-up: Geochemical and O-Hf isotopic constraints from Cretaceous plutons in southern Korea     

《地学前缘(英文版)》2023,14(1):101492

Northeast Asian continental margins contain the products of magma emplacement driven by prolonged subduction of the (paleo-)Pacific plate. As observed in many Cordilleran arcs, magmatic evolution in this area was punctuated by high-volume pulses amid background periods. The present study investigates the early evolution of the Cretaceous magmatic flare-up using new and published geochronological, geochemical, and O-Hf isotope data from plutonic rocks in the southern Korean Peninsula. After a long (～50 m.y.) magmatic hiatus and the development of the Honam Shear Zone through flat-slab subduction, the Cretaceous flare-up began with the intrusion of monzonites, granodiorites, and granites in the inboard Gyeonggi Massif and the intervening Okcheon Belt. Compared to Jurassic granitoids formed during the former flare-up, Albian (～111 Ma) monzonites found in the Eopyeong area of the Okcheon Belt have distinctly higher zircon ε_Hf(t) (?7.5 ± 1.3) and δ¹⁸O (7.78‰ ± 0.25‰) values and lower whole-rock La/Yb and Sr/Y ratios. The voluminous coeval granodiorite and granite plutons in the Gyeonggi Massif are further reduced in Sr/Y and to a lesser extent, in La/Yb, and have higher zircon ε_Hf(t) values (?13 to ?19) than the Precambrian basement (ca. ?30). These chemical and isotopic features indicate that Early Cretaceous lithospheric thinning, most likely resulting from delamination of tectonically and magmatically overthickened lithospheric keel that was metasomatized during prior subduction episodes, and consequent asthenospheric upwelling played vital roles in igniting the magmatic flare-up. The O-Hf isotopic ranges of synmagmatic zircons from the Albian plutons and their Paleoproterozoic and Jurassic inheritance attest to the involvement of lithospheric mantle and crustal basement in magma generation during this decratonization event. Arc magmatism then migrated trenchward and culminated in the Late Cretaceous, yielding widespread granitoid rocks emplaced at shallow crustal levels. The early Late Cretaceous (94–85 Ma) granites now prevalent in Seoraksan-Woraksan-Sokrisan National Parks are highly silicic and display flat chondrite-normalized rare earth element patterns with deep Eu anomalies. Synmagmatic zircons in these granites mimic their host rock’s chemistry. Delamination-related rejuvenation of crustal protoliths is indicated by zircon ε_Hf(t) values of granites (?6 to ?20) that are consistently higher than the Precambrian basement value. Concomitant core-to-rim variation in zircon O-Hf isotopic compositions reflects a typical sequence of crustal assimilation and fresh input into the magma chamber.  相似文献   

甘肃北山地区早白垩世松柏类植物Podozamites(苏铁杉属)及其古气候意义^*          下载免费PDF全文

李爱静  杜宝霞  张明震  林少华  彭静  张静  刘国龙  交巴顿珠  马国蓉  惠建国 《古地理学报》2023,25(2):485-496

Podozamites(苏铁杉属)为松柏类已灭绝的形态属,是北半球中生代植物群中的重要分子。经鉴定,甘肃北山地区早白垩世早期地层中产出的Podozamites包括Podozamites sp.(苏铁杉未定种)、Podozamites aff. distans(间离苏铁杉相似种)和Podozamites bullus(美丽苏铁杉)3个种。基于Podozamites大化石记录和古地理分布特征,结合中生代古气候分区,对该属的古气候意义进行综合分析。结果表明: 晚三叠世—中侏罗世,Podozamites数量较为丰富,主要集中分布于北半球温暖湿润气候区; 晚侏罗世—早白垩世,随着干热气候带的扩张,Podozamites丰度下降,分布区域也随温热潮湿气候区变迁而发生迁移。推测Podozamites在中生代的古地理分布主要受到温暖潮湿气候带变迁的影响,其更加适宜生存于温暖湿润的气候条件下,可作为温暖湿润气候的指示分子。  相似文献   

Zircon U-Pb ages,geochemistry, and Sr-Nd isotope ratios for early cretaceous magmatic rocks,southern Saqqez,northwestern Iran     

《Chemie der Erde / Geochemistry》2021,81(1):125687

Sanandaj-Sirjan Zone (SaSZ) is one of the most dynamic structural zones of Iran, which is divided into three main parts: Northern, Central and Southern. The northern SaSZ has been affected by deformation due to fault activities near the Zagros suture zone, and mylonitic structures have overprinted these rocks and was affected by three episodes of magma injection during the Permian-Carboniferous, Early Cretaceous and Cenozoic. In this study, the rock units investigated that have been considered Precambrian-Paleozoic basement on geological maps. This paper considers zircon U-Pb dating, whole-rock chemistry and Sr-Nd isotope ratios of Cretaceous magmatic rocks in the N-SaSZ to develop a new geodynamic model for the evolution of these magmatic rocks. The new zircon U-Pb ages obtained in this study show that the magmatic rocks crystallized at 115–107 Ma in the Early Cretaceous (Aptian-Albian) and are much younger than the supposed ages presented on geological maps. This complex classified into two main groups of basic-intermediate and acidic rocks based on SiO₂ contents. The whole-rock chemistry of the basaltic and andesitic rocks, which are interbedded with marine shallow-water sedimentary deposits, shows their typical calc-alkaline affinity and subordinate tholeiitic series on an active margin. The positive ε_Nd(t) of approximately +4 for some undifferentiated basalts with negative Ti and Nb anomalies shows the relation of these rocks to calc-alkaline magmatism and was generated by the partial melting of subcontinental lithospheric mantle (SCLM). Granitoid rocks with some affinity to the peraluminous group with a negative ε_Nd(t) value (-3.2) mainly and negative Ti and Nb anomalies plot in an active margin tectonic setting. Simultaneous mafic calc-alkaline volcanism and the generation of granitic intrusions in the Early Cretaceous could have occurred on an active margin. Due to the absence of Jurassic arc related magmatic rocks in northern SaSZ and presence of Cretaceous calc alkaline magmatic activity, which are not observed in the central SaSZ, support the idea that the subduction of the Neotethys beneath the northern SaSZ started in the Early Cretaceous.  相似文献   

陆棚海泥岩的岩相特征及沉积过程     

李志扬 《沉积学报》2021,39(1):168-180

传统的沉积模式认为大部分细粒沉积岩（泥岩或页岩）的沉积发生在相对深水、低能的环境中。作为地表上分布最为广泛的沉积岩类型,泥页岩包含了对重构地质历史时期古地理、古气候的重要信息。泥页岩除了可以作为有效的烃源岩,勘探开发技术的进展更发掘出泥岩作为非常规油气储层的巨大潜力。近十年来,国内外对细粒沉积物的水槽实验、泥岩沉积微相的精细分析、以及泥岩岩相组成特征的研究取得了长足的进展。这些研究对泥岩的沉积过程和沉积模式在不同角度上提供了新的认知。大部分泥岩（甚至包括众多有机质含量高的泥岩）都可能沉积在相对浅水以及水动力条件相对较高的环境中。不同的沉积过程（底部水流）形成不同的泥岩沉积微相,并对有机质在泥岩中的埋藏富集具有重要的控制作用。以晚白垩纪北美西部内陆海道为例,总结在陆棚浅海环境中（最大水深< 200 m）,位于从近岸到远岸（> 500 km）不同沉积环境（包括前三角洲/下邻滨、内陆棚、中陆棚、和外陆棚环境）中的泥岩的主要沉积过程、沉积微相特征、以及富集有机质的潜力。由于沉积过程和沉积环境是决定泥岩成分、沉积相、和岩石物理特征非均质性的首要因素,不同浅海环境中的泥岩相特征和沉积模式可有助于利用泥岩地层进行古地理、古气候的重构,并能够对预测不同陆棚浅海环境中沉积的泥岩作为有效烃源岩或有效储层的潜力提供指导。  相似文献