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11.
内蒙古"宝音图隆起"的归属讨论 总被引：5，自引：0，他引：5
对比研究表明，内蒙古“宝音图隆起”和狼山地区的古元古代宝音图岩群与新太古代色尔腾山岩群都是由中低级变质的各种片岩、大理岩组成，一致的岩石组合和变质相暗示二者可能是等同物而不是两个岩群。以物探资料为据的构造研究也证实，“宝音图隆起”与狼山地区之间并无槽一台级的大型断裂构造分开，二者实为统一的构造整体而不是分属槽台，只因两侧被两条近于平行的NE向断裂围限，使其总构造线方向呈NE或NNE向而与色尔腾山的构造线不同。结论认为，“宝音图隆起”仍是华北陆块的一部分，不属于内蒙古一大兴安蛉地槽褶皱系。 相似文献
12.
DONG Shao-peng ZHANG Pei-zhen ZHENG Wen-jun YU Zhong-yuan LEI Qi-yun YANG Hui-li LIU Jin-feng GONG Hui-ling 《地震地质》2018,40(6):1216-1239
The Langshan range-front fault (LRF)is a Holocene active normal fault that bounds the Langshan Mountain and Hetao Basin at the northwest corner of the Ordos Plateau. Paleoseismic trenching research at three sites, Dongshen Village trench (TC1), Qingshan trench (TC2)and Wulanhashao trench (TC3)from north to south was performed in this study to reveal the seismic hazard risk in Hetao Basin. The paleoevents ED1, ED2, ED3 from TC1 can be constrained to have occurred (6±1.3)ka, (9.6±2)ka and (19.7±4.2)ka respectively, while the paleoevent EQ1 from TC2 occurred about (6.7±0.1)ka and the paleoevents EW1, EW2, EW3 at TC3 took place about (2.3±0.4)ka, (6±1)ka and before 7ka respectively. In combination with paleoseismic results of previous researchers, the Holocene earthquake sequence of the LRF could be established as 2.3~2.43ka BP (E1), 4.41~3.06ka BP (E2), 6.71~6.8ka BP (E3), 7.6~9.81ka BP (E4), and (19.7±4.2)ka BP (E5). Although the possibility of missing events cannot totally be ruled out, based on the analysis on faulted geomorphology at Wulanhashao site, we argue the paleoearthquake history of the LRF during Holocene may be complete with an average recurrent interval about 2500 yrs. The apparent displacements associated with events E1, E3 and E4 are significantly larger than that of event, E2, that suggests that they might be great events with magnitudes 7.5 to even over 8 that ruptured the entire LRF, while the event E2 may be a smaller event that only ruptured a segment of the fault. The magnitude of event E2 might be about M7. This poses a significant seismic hazard to the area of the Linhe depression in the western Hetao graben region. With the further limitation of previous radiocarbon dating result near our trench site at Wulanhashao, the slip rate at Wulanhashao should be not smaller than, but close to 0.66mm/a since 15ka BP. And the slip rate at Qingshan site is supposed to be about 1.4~1.6mm/a since 6.8ka BP. Both our combined most recent paleoseismic cognition and current tectonic geomorphologic research results supports to reveal that the Langshan range-front fault now is an unsegmented fault, preferring to rupture the whole fault in a surface-rupture event. Considering the most recent event E1 and fault slip rate obtained above, the accumulated strain on the LRF could be estimated as about 1.52~3.94m. Given the ~2500a recurrent interval, we argue that the elapsed time since last major quake, E1, is approaching or even over the recurrence, and the seismic risk for another major quake is imminent, at least cannot be ignored. 相似文献
13.
古—中元古代时期是地质历史上最重要的铅-锌硫化物爆发性成矿阶段, 位于我国华北板块北缘西段的狼山多金属成矿带是这个时期的典型案例。作为成矿带内最大的硫化物矿床, 炭窑口和东升庙矿床赋矿层位和矿化特征一致, 被认为是同一个次级盆地内一次大型热液成矿事件的产物。这两个矿床所赋存的数亿吨硫化物矿石均不同程度富集重S同位素(平均值＞+30‰), 而对于矿石硫的具体来源及34S富集机制尚存争议。本文对炭窑口围岩和矿石中黄铁矿进行了Fe-S同位素研究, 对其沉积-成岩环境和矿化过程给出综合制约。炭窑口碳质板岩中粗粒黄铁矿δ56FeIRMM值在?0.51‰ ~ ?0.15‰之间, δ34SV-CDT值在+35.0‰ ~ +39.6‰之间, 相比东升庙矿床围岩中不规则黄铁矿明显富集轻Fe同位素且更加富集重S同位素, 可能是盆地边缘、相对氧化的浅水环境下Fe以氧化态几乎完全沉淀后成岩期转化的产物。该认识与炭窑口矿区常见层状重晶石所指示的比东升庙更加氧化的盆地边缘浅水环境一致。本文认为炭窑口矿石与围岩中硫化物均强烈富集重S同位素(δ34SV-CDT值均在+26.6‰ ~ +41.0‰之间)表明成岩环境同样是矿石硫化物结晶沉淀的主战场, 其中半局限环境中浓缩海水硫酸盐在较封闭成岩条件下被甲烷为主的还原剂几乎完全还原。“局限盆地+成岩环境”模式可以解释炭窑口—东升庙盆地围岩和矿石均异常富集重S同位素的特征。前人报道的与成矿关系密切的碳酸盐相对富集轻C同位素所指示的有机碳参与成矿为成岩环境成矿提供了可靠证据。尽管不能完全排除细菌还原硫酸盐的作用, 炭窑口—东升庙盆地各个层位围岩与矿石轻S同位素完全缺失表明开放体系细菌还原作用导致的硫化水体环境主导成矿的可能性较小。 相似文献
14.
狼山构造带是华北地台北缘巨型造山带的重要组成部分，韧性剪切带是狼山构造带内的主要构造形式之一，是地壳深层次构造的反映.对狼山Ⅱ号韧性剪切带西南缘糜棱岩化硅质条带状灰岩进行地球化学特征研究，以探讨不同变形强度的糜棱岩化硅质条带状灰岩与原岩的成分变异规律.常量元素、微量元素和稀土元素分析结果表明，与原岩中常量元素和微量元素含量相比较，变形强度不同的硅质条带状灰岩存在着差异变化.变形岩石中常量元素仅CaO为带出组分，其他均为带入组分；微量元素中富集Rr、Sr、Ba、Pb、Ti、Cr、Cu、Nb、Ta、Zr、Hf元素，Ni元素相对亏损.变形的硅质条带状灰岩与原岩的稀土元素配分模式图基本一致，表现为轻稀土元素富集、重稀土元素亏损的右倾斜曲线，具有明显的负Eu异常特征，表明稀土元素在韧性剪切过程中具有一定的相对稳定性和同源性. 相似文献
15.
狼山地区位于内蒙古阿拉善地块东北缘,其构造背景一直存在争议。报道狼山地区枕状玄武岩的锆石U-Pb年龄、地球化学研究成果。LA-ICP-MS锆石U-Pb定年结果表明,玄武岩中的锆石大多为捕获基底的锆石。根据锆石特征及侵入玄武岩的花岗岩年龄,得出玄武岩年龄为254～252Ma,属于二叠纪晚期。枕状玄武岩具有贫碱低钾的特征,亏损Nb、Ta、Ti、P,富集Rb、Ba、U等元素,富集轻稀土元素、亏损重稀土元素,具弱负Eu异常,显示岛弧玄武岩特征。初步认为玄武岩形成于活动大陆边缘弧环境,为古亚洲洋向南俯冲的产物,指示阿拉善地块北缘在二叠纪晚期为大陆边缘弧,为研究阿拉善地块东北缘晚古生代构造背景提供了证据。 相似文献
16.
西藏措勤盆地色林错凹陷郎山组分子地球化学特征 总被引：4，自引：0，他引：4
措勤盆地是青藏高原内第二大海相含油气盆地,郎山组碳酸盐岩是盆地内重要的烃源岩。盆地东部的色林错凹陷保存条件好,前人还很少在该区开展石油地质研究。应用GC和GC—MS技术,对该凹陷内雄梅地区郎山组烃源岩抽提物进行了生物标志物的研究。研究表明,该区郎山组有机质母质主要为海相藻类,也有少量高等植物的混入;主要形成于缺氧,盐度较高的咸水环境,有机质成熟度较高,经历了1~2级的生物降解作用。因此,结合其它有机地球化学参数、沉积和构造条件,考虑到风化作用因素,郎山组烃源岩应具有较好的生油潜力,这对该区油气勘探具有重要意义。 相似文献
17.
内蒙古狼山地区浩日格山二长花岗岩的地球化学特征、LA- ICP- MS锆石U- Pb定年及Hf同位素组成 总被引：1，自引：0，他引：1
内蒙古狼山地区浩日格山岩体位于中亚造山带南缘及华北北缘的结合位置,对其进行系统的岩石地球化学探讨有助于加深对中亚造山带晚古生代—早中生代构造- 岩浆演化及地球动力学背景的认识。该岩体主体岩性为二长花岗岩,可进一步划分为二云母二长花岗岩及斑状黑云母二长花岗岩,LA- ICP- MS锆石U- Pb测年分别获得二者的206Pb/238U加权平均年龄为244.9±1.6Ma及230.2±1.5Ma,指示其形成于三叠纪早—中期。地球化学分析结果表明,浩日格山二长花岗岩SiO2含量介于72.58%~74.42%之间,K2O含量为4.06%~5.82%,Na2O含量为3.08%~3.88%,Al2O3含量为13.39%~14.55%,具有高钾钙碱性和过铝质特征。岩石稀土总量较低,轻稀土相对富集,重稀土相对亏损,具有较明显的负铕异常。岩体富集Rb、U、Hf;亏损Ba、Nb、Ta、Ti和Zr,显示出高分异花岗岩的特点。锆石Hf同位素分析结果显示：εHf(t)值总体为负值,并且与华北北缘三叠纪花岗岩εHf(t)值基本一致,表明源区主要为华北古老地壳。对浩日格山二长花岗岩的研究表明狼山地区在三叠纪早—中期为后碰撞构造环境,可能与古亚洲洋的最终闭合关系密切。 相似文献
18.
Geomorphological signatures of the evolution of active normal faults along the Langshan Mountains,North China 总被引：2，自引：0，他引：2
Segmentation, propagation, and linkage of normal faults often occur in regions of active extension, and observations of the distribution and structural properties of segment boundaries can provide important insights for seismic hazard assessment. In this study, we carry out quantitative geomorphological analysis to evaluate the relative tectonic activity along the Langshan Piedmont Fault (LPF), which bounds the NW margin of the Hetao Graben, North China. On the basis of obtained morphometric indices (HI, BS, Smf, VF, SLK, and χ), tectonic knickpoint heights, footwall topography, and small unmanned aerial vehicles (sUAV)-based field observations, we demonstrate that: (i) The Langshan landscape is in a state of disequilibrium in response to active rock uplift and channel incision; (ii) The LPF consists of two major fault segments with lengths of 65 and 95 km, respectively, which likely have been linked with each other; (iii) Rupturing of the whole of one segment can generate an earthquake of Mw ~7.3–7.5, and earthquake magnitude may reach Mw ~7.8 if the entire fault trace of ~160 km is ruptured, posing a significant seismic risk in the western Hetao Graben. These findings would further our understanding of normal fault evolution through space and time in actively extending regions. 相似文献
19.
Late Cretaceous‐Cenozoic Multi‐Stage Denudation at the Western Ordos Block: Constraints by the Apatite Fission Track Dating on the Langshan 总被引：1，自引：0，他引：1
CUI Xianyue ZHAO Qihu ZHANG Jin WANG Yannan ZHANG Beihang NIE Fengjun QU Junfeng ZHAO Heng 《《地质学报》英文版》2018,92(2):536-555
The apatite fission track dating of samples from the Dabashan(i.e., the Langshan in the northeastern Alxa Block) by the laser ablation method and their thermal history modeling of AFT ages are conducted in this study. The obtained results and lines of geological evidence in the study region indicate that the Langshan has experienced complicated tectonic-thermal events during the the Late Cretaceous-Cenozoic. Firstly, it experienced a tectonic-thermal event in the Late Cretaceous(~90–70 Ma). The event had little relation with the oblique subduction of the Izanagi Plate along the eastern Eurasian Plate, but was related to the Neo-Tethys subduction and compression between the Lhasa Block and Qiangtang Block. Secondly, it underwent the dextral slip faulting in the Eocene(~50–45 Ma). The strike slip fault may develop in the same tectonic setting as sinistral slip faults in southern Mongolia and thrusts in West Qinling to the southwest Ordos Block in the same period, which is the remote far-field response to the India-Eurasia collision. Thirdly, the tectonic thermal event existed in the late Cenozoic(since ~10 Ma), thermal modeling shows that several samples began their denudation from upper region of partial annealing zone(PAZ), and the denudation may have a great relationship with the growth of Qinghai-Tibetan Plateau to the northeast. In addition, the AFT ages of Langshan indicate that the main body of the Langshan may be an upper part of fossil PAZ of the Late Cretaceous(~70 Ma). The fossil PAZ were destroyed and deformed by tectonic events repeatedly in the Cenozoic along with the denudation. 相似文献
20.
内蒙古狼山地区乌花辉长岩体主要由橄榄辉长岩和角闪辉长岩组成,其锆石LA-ICP-MS U-Pb同位素测年结果表明,岩体形成于(319.8±1.8)~(325.4±1.6) Ma,属于早石炭世末期岩浆活动的产物。地球化学特征上,乌花辉长岩属低钾钙碱性玄武岩系列,具有较高的Mg#(多在76.70~80.35之间)、Al2O3(13.55%~25.13%)和较低的TiO2(0.18%~1.35%)。稀土总含量较低(∑REE= 8.92×10-6~40.10×10-6),稀土元素分馏程度不高,呈现出轻稀土元素(LREE)略微富集、重稀土元素(HREE)相对亏损((La/Yb)N = 1.74~3.06)的特点,Eu呈明显的正异常(δEu=1.156~3.86)。岩石富集Pb和K、Rb、Ba、Sr等大离子亲石元素,明显亏损Nb、Ta、Zr、Hf、Th等高场强元素,较低的Zr含量(4.38×10-6~26.6×10-6)和Zr/Y比值(1.08~2.35),呈现出典型的俯冲-消减带弧火山岩的地球化学特征。Sr-Nd-Hf同位素研究表明,乌花辉长岩岩浆源区为富集地幔,在侵位过程中受到的地壳混染程度较弱。结合区域地质背景,认为乌花辉长岩为俯冲-消减构造体制下由俯冲带流体交代富集地幔部分熔融而成,代表了俯冲相对早期阶段的产物,指示华北板块北缘西段在早石炭世晚期开始进入到安第斯型活动大陆边缘阶段,并可能结束于早二叠世之前。 相似文献