Tracing a late Mesozoic magmatic arc along the Southeast Asian margin from the granitoids drilled from the northern South China Sea     

《International Geology Review》2012,54(1):71-94

Abstract

The granitoid suites encountered by drilling in the northern South China Sea (SCS) remain important for understanding the evolution of the late Mesozoic Southeast Asian continental margin. They comprise a range of rock types including diorite, tonalite, granodiorite, monzogranite and syenogranite with SiO₂ spanning 56.4–76.8%. Newly acquired secondary ion mass spectrometry (SIMS) U–Pb ages of samples from 14 boreholes indicate two key magmatic episodes: Late Jurassic (161.6–148.2 Ma) and Early Cretaceous (136.5–101.7 Ma). Jurassic magmatism probably began in late Middle Jurassic time, documented by the dates of inherited zircons. The granitoids are dominated by metaluminous to weakly peraluminous I-type granites, are transitional between magnesian and ferroan, and encompass calc-alkaline, high-K calc-alkaline, and shoshonitic series. The geochemical signatures suggest that these granitoids were mostly generated in a normal continental arc environment. Notable features of the I-type samples are well-defined negative Nb–Ta–Ti anomalies typical of arc-related magmas. Taken together, the late Mesozoic arc granites of the SCS, the accretionary wedge of the Palawan terrane to the southeast, and the zone of lithospheric extension north of the SCS throughout Southeast China, define a southeast-to-northwest trench-arc-backarc architecture for the late Mesozoic Southeast Asian continental margin whose geodynamic setting is related to subduction of the Palaeo-Pacific slab beneath the Asian continent. Two key subduction episodes are recognized, one in Late Jurassic and the other in Early Cretaceous time.  相似文献   

岷江断裂带晚新生代逆冲推覆构造：来自钻孔的证据   总被引：6，自引：0，他引：6  

张岳桥  李海龙  吴满路  廖椿庭 《地质论评》2012,58(2):215-223

岷江断裂带由2个不同性质的断裂组成:早期岷江逆冲断裂和晚期岷江正断裂。野外地质调查和钻孔资料发现在岷江西侧山麓之下存在一套厚度大于110m的早更新世灰黑色湖相地层,三叠系灰岩逆掩在这套湖相地层之上。由此确定岷江断裂是一条西倾的逆冲断层,逆冲作用发生在中更新世之前。在中更新世时期,岷江逆冲断裂发生构造负反转,在其前缘形成一条东倾的正断层,它控制了岷江上游漳腊盆地的发育。本文认为,岷山地区现今地震活动并非受控于岷江断裂带,而可能受到虎牙断裂及岷山隆起深部滑脱构造的控制,岷江断裂带位于该深部滑脱构造的上部。进而认为逆冲—推覆构造样式可能是青藏高原东缘晚新生代造山和快速隆升的主要变形机制。  相似文献   

中国西部叠合盆地油气多期成藏模式及勘探有效性     

康德江  姜丽娜  张金友 《沉积学报》2012,30(1):166-178

我国西部叠合盆地油气资源丰富,随着勘探难度逐年增加,如何准确定位有利成藏区带对增加勘探成功率至关重要。通过对比叠合盆地主要大中型油气田发现,叠合盆地大都为多期成藏,且晚期成藏有利于油气规模化保存。在大量总结叠合盆地多个油气成藏过程、特点和模式的基础上,结合研究区带的构造演化特点,按照叠合盆地构造变动模式划分,将西部叠合盆地油气多期成藏模式划分为5种,分别是油气连续充注型、早期强烈改造型、中期强烈改造型、晚期强烈改造型和多期充注改造交替型。在晚期成藏有利于油气勘探的前提下,分析认为具有油气连续充注型油气成藏的区域和周边地区由于构造变动轻微,破坏幅度最小,因此油气藏类型较多,规模化可能性最大,最具油气勘探有效性,而多期充注改造交替型成藏模式在构造变动频繁剧烈的影响下,使得油气藏破坏量较大,保存下来的可能性很小,因此也最不具备勘探有效性,此类地区应该尽可能规避。  相似文献   

西藏玛旁雍错沉积揭示的晚冰期以来环境变化     

朱少航  朱立平  王君波  鞠建廷  马庆峰  陈浩  许腾  开金磊 《第四纪研究》2019,(3):602-614

玛旁雍错位于青藏高原西南部,是研究印度季风演化的理想地区之一。利用活塞采样器在玛旁雍错75 m水深处获取了一根4.69 m长岩芯,利用^210Pb和AMS^14C测年确定了岩芯的年代,根据元素含量(XRF扫描)、总有机碳(TOC)、总无机碳(TIC)和总氮(TN)等代用指标,重建了该地区14 cal.ka B.P.以来气候环境变化。结果显示,冰消期(14~12 cal.ka B.P.),TOC和TIC含量变化显示了湖区环境整体上较为暖湿;12.0~11.4 cal.ka B.P.,径流明显减弱,可能是新仙女木事件的反映;早中全新世(11.4~3.4 cal.ka B.P.),湖区环境整体上以暖湿为主,气候有所波动,出现了两次冷事件(10.2~9.8 cal.ka B.P.和8.2 cal.ka B.P.左右),7.4~6.6 cal.ka B.P.,出现了一个暖时期;晚全新世(3.4~0 cal.ka B.P.),湖区环境整体上趋向于干旱化,并伴有两次相对湿润时期(2.6~2.0 cal.ka B.P.和1.4~1.0 cal.ka B.P.)。玛旁雍错环境变化表明,晚冰期以来(14.0~3.4 cal.ka B.P.),受到太阳辐射的影响,印度季风带来的降水以及冰川融水较多,湖区环境较为湿润,整体上有利于内源生物的生存;晚全新世(3.4~0 cal.ka B.P.),北半球夏季太阳辐射量减少,印度季风减弱,径流减弱,湖区环境朝干旱化方向发展。  相似文献   

青海共和盆地干热岩赋存地质特征及开发潜力   总被引：4，自引：1，他引：3  

张盛生  张磊  田成成  蔡敬寿  唐保春 《地质力学学报》2019,25(4):501-508

青海共和盆地贮藏有丰富的干热岩地热资源。为提升共和盆地干热岩地热资源成因的理论认识,进一步推动干热岩资源的勘探,文章从共和盆地干热岩热源机制、盖层条件、储层特征等方面对共和盆地干热岩资源成因件进行了全面分析。首先,结合区域地质构造分析、地热地质调查、地球物理（航磁、地震）解译等手段,在共和盆地恰卜恰岩体内实施了4口深度为2927~3705 m的干热岩勘查孔,并在3705 m处钻获236℃的优质干热岩资源,为中国非现代火山区干热岩地热资源勘探的首个重大突破。其次,系统测试了钻孔不同深度花岗岩放射性,结果表明,共和盆地花岗岩体铀、钍、钾放射性含量略高于大地背景值,放射性生热率较低,对干热岩热源的贡献小,其热源可能来自壳内熔融体。第三,基于地质资料分析和航磁解译,圈定了共和盆地总体面积约1.4×104 km2的潜在干热岩分布区。最后,采用体积法评估了共和盆地干热岩资源潜力,结果表明,共和盆地3.0~6.0 km深度范围保守的、静态干热岩资源总量为8974.74×1018 J,换算标准煤可达3066.19×108 t,具有广阔的开发利用前景。   相似文献   

内蒙古阿鲁科尔沁旗林西组碎屑岩LA-ICP-MS锆石 U-Pb年龄及构造意义          下载免费PDF全文

张海华  郑月娟  张健  苏飞  黄欣  卞雄飞  公繁浩 《高校地质学报》2019,25(1):14

阿鲁科尔沁旗陶海营子剖面以灰、灰黑、黄绿色的砂板岩组合为特征,是林西组典型剖面之一,含双壳、叶肢介、 植物和孢粉化石,时代为晚二叠世晚期。对采自剖面上部第61 层的长石岩屑砂岩中的锆石进行了LA-ICP-MS U-Pb 同位素 测试,获得了96 颗锆石的谐和-近谐和年龄,同时引用该剖面第1 层已发表碎屑岩97 颗锆石数据,共计193 个碎屑锆石数据 年龄统一分析。193 颗碎屑锆石按年龄值和频率分布特征可分为五组：248~302 Ma （80 颗,41%）,峰值年龄为263 Ma; 312~388 Ma（24颗,12%）; 417~523 Ma（26颗,13%）;564~991 Ma（38颗,20%）;1000~2775 Ma （25颗,13%,207Pb /206Pb 年龄）。最小年龄段年龄的加权平均值为263±1.7 Ma （MSWD=1.7, n=80）,与最小的峰值263Ma 年龄相吻合,推测测年样品 沉积时间下限为263 Ma,表明其沉积时代应为晚二叠世。碎屑锆石年龄谱值表明其沉积物源具多样性和复杂性,主体应来 自东北各地块,同时存在华北板块和西伯利亚板块的物源信息（1637±26 Ma,1791±24 Ma,1927±31 Ma,1954±24 Ma, 2089±31 Ma,2671±21 Ma,2775±21 Ma）。本次获得最年轻的一组碎屑锆石的峰值年龄为263 Ma,表明华北板块与西伯利亚 板块的最终闭合时间应该在晚二叠世之后。  相似文献   

Late Ordovician and Early Devonian conodonts from Onoo Tolgoi area of Mongolia     

Dorjsuren Byambadash  Bujinlkham Boijir  Yadamjav Dagva-Ochir  Horlod Yadam 《东北亚地学研究》2008,11(1):1-13

Conodont samples were collected from three localities in the Onoo Tolgoi area, Mongolia, and many conodonts have been found. Conodonts from the Onoo Tolgoi Formation （M288-M294） lack index fossils; its age could be Late Silurian. Samples from the Hutul us hudag Formation （M295-M299） contain Ozarkodina pandora alpha Morph. （ P element）, clearly indicating that this formation is Early Devonian late Lochkovian in age. Samples collected from so-called Silurian Onoo Tolgoi Formation at other localities （M300-M303） yield many Ordovician conodonts, including Icriodella baotaensis, Icriodella cf. baotaensis, Eoplacognathus fianyeen- sis, Eoplacognathus protoramosus ; Baltoniodus alobatus ; and ？ Ambalodus triangularis ; the age is Late Ordovician, more precisely, early-middle Late Ordovician.  相似文献   

New insights on late Quaternary palaeogeographic setting in the Northern Adriatic Sea (Italy)     

Sara Picone  Francesca Alvisi  Enrico Dinelli  Caterina Morigi  Alessandra Negri  Mariangela Ravaioli  Carmela Vaccaro 《第四纪科学杂志》2008,23(5):489-501

Sedimentological, geochemical and micropalaeontological data from sediment cores in the northwestern Adriatic Sea were obtained to reconstruct the stratigraphic framework and palaeogeographic setting during the last post‐glacial sea‐level rise (14000–6000 yr BP). Four lithostratigraphic units were identified: (a) distal plain deposits (>14000 yr BP), submerged during the first phases of marine ingression; (b) coastal lagoon system; (c) barrier‐lagoon system, which is dated back to between 10019 ± 61 and 10228 ± 174 cal. yr BP from ¹⁴C dating on peat and shell remains; (d) marine prodelta deposits (<5500 yr BP). Geochemical data allow the identification of three distinct sediment sources: River Po, River Adige and Eastern Alpine rivers characterised by decreasing Ni/Mg ratios (50–70, 8–15 and 5–10, respectively) and Ba/Al ratios of 45–55, 55–65 and 35–45, respectively. The three sources display different relative abundances in time. During the Lateglacial, the Po is the main sediment source for the southern cores, whereas the Eastern Alps and the River Adige are the main sediment sources for the northern cores. This suggests a northern position of the Po River bed compared to previous studies. Coastal drowning led to a homogenization of the provenance signal within the sediments. Only after the marine transgression does a River Po signal appear in the northern cores. At the same time, in the southern cores the signal of Eastern Alpine rivers becomes stronger. Transgressive barrier‐lagoon and recent sediments do not display a predominant signal for provenance indicators. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Late Quaternary speleothem pollen in the British Isles     

Christopher J. Caseldine  Siobhán F. McGarry  Andy Baker  Chris Hawkesworth  Peter L. Smart 《第四纪科学杂志》2008,23(2):193-200

As with many terrestrial areas, the British Quaternary sequence is characterised by incomplete, fragmentary records, whose correlation is based on stratigraphic or biostratigraphic techniques due to the lack of radiometric ages beyond the ～40 kyr limit of ¹⁴C dating. Speleothems (secondary cave calcite deposits) offer a significant advantage over many sources of palaeoenvironmental information; they can be dated to a high precision and accuracy by uranium‐thorium (²³⁸U‐²³⁰Th) thermal ionisation and inductively coupled plasma (ICP) mass spectrometry in the time period back to 500 kyr. They may also contain sufficient well‐preserved pollen representative of contemporary vegetation above the cave to allow palaeoenvironmental reconstruction. This study adopts the novel approach of combining pollen and thermal ionisation mass spectrometric (TIMS) U‐Th dating of British speleothems to produce well‐constrained palaeoenvironmental records. We report for the first time precisely dated records of pollen assemblages from speleothems suggesting the presence of thermophilous arboreal species in phases previously considered to have been consistently cool or cold and devoid of trees. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

辽宁东部地区桥头组微生物诱发沉积构造(MISS）的发现及意义     

吴子杰  张德明  范海滨  张国仁  邱隆伟  王海鹏  仲米山  耿树峰  郑伟  高福亮  赵汉卿 《地质论评》2022,68(2):2022030023-2022030023

Through the re-investigation and understanding of the “mud crack-like sedimentary structure” in the Qiaotou Formation from late Mesoproterozoic to early Neoproterozoic in the eastern Liaoning, and by comparing with the contemporaneous microbial induced sedimentary structure (MISS) in other areas of the NCC, For the first time, the fractured sedimentary structure discovered in the Qiaotou Formation in Liaoning was identified as MISS.Results: The fissure structure found in the Qiaotou Formation is MISS, which is formed by the physical destruction of microbial mats.Conclusions: The MISS identified in the Qiaotou Formation has spindle-like, three-connected ornithoid and partially connected branched morphology, so it is speculated that the Qiaotou Formation was formed in the sedimentary environment of the upper part of the supratidal zone. This discovery provides basis for stratigraphic and sedimentological studies of the Qiaotou Formation, and is of great significance for studying the evolution of early life on earth and exploring the long-term impact of biota on the atmosphere and hydrosphere.  相似文献