秋季红沿河核电站海域水龄分布及其对水母丰度分布的影响     

邱敏志  苏薇  姚庆祯  王彦涛  张广跃  许博超  张晓洁 《海洋学报》2020,42(4):122-127

本研究调查了秋季红沿河核电站海域镭、氡同位素的活度水平及分布情况，结合镭同位素表观年龄模型计算该海域的水体年龄，进而得出研究区域的水体运移方向，初步探讨了水母丰度分布与水体运移的相关关系。得到结论如下:(1)红沿河核电站海域表层水体中224Ra、226Ra及222Rn的活度水平分别为2.9～62.4 dpm/(100 L)，11.9～57.4 dpm/(100 L)及0.1～1.3 dpm/L，镭同位素活度呈现出近岸高、远岸低的分布趋势，氡同位素的分布则更大程度上受水温控制；(2)通过224Ra/226Ra表观年龄模型计算得出红沿河海域表层水体年龄范围介于0～16 d，平均年龄(10.9±3.6) d，水体主体流向为北偏东方向，流速为7.2 cm/s；(3)水母丰度分布与水体流向呈现出较为一致的对应关系，在主体流向方向上，水体年龄较大的海域水母丰度最高。  相似文献   

The Creston,California, meteorite fall and the origin of L chondrites     

Peter Jenniskens  Jason Utas  Qing‐Zhu Yin  Robert D. Matson  Marc Fries  J. Andreas Howell  Dwayne Free  Jim Albers  Hadrien Devillepoix  Phil Bland  Aaron Miller  Robert Verish  Laurence A. J. Garvie  Michael E. Zolensky  Karen Ziegler  Matthew E. Sanborn  Kenneth L. Verosub  Douglas J. Rowland  Daniel R. Ostrowski  Kathryn Bryson  Matthias Laubenstein  Qin Zhou  Qiu‐Li Li  Xian‐Hua Li  Yu Liu  Guo‐Qiang Tang  Kees Welten  Marc W. Caffee  Matthias M. M. Meier  Amy A. Plant  Colin Maden  Henner Busemann  Mikael Granvik   《Meteoritics & planetary science》2019,54(4):699-720

It has been proposed that all L chondrites resulted from an ongoing collisional cascade of fragments that originated from the formation of the ~500 Ma old asteroid family Gefion, located near the 5:2 mean‐motion resonance with Jupiter in the middle Main Belt. If so, L chondrite pre‐atmospheric orbits should be distributed as expected for that source region. Here, we present contradictory results from the orbit and collisional history of the October 24, 2015, L6 ordinary chondrite fall at Creston, CA (here reclassified to L5/6). Creston's short 1.30 ± 0.02 AU semimajor axis orbit would imply a long dynamical evolution if it originated from the middle Main Belt. Indeed, Creston has a high cosmic ray exposure age of 40–50 Ma. However, Creston's small meteoroid size and low 4.23 ± 0.07° inclination indicate a short dynamical lifetime against collisions. This suggests, instead, that Creston originated most likely in the inner asteroid belt and was delivered via the ν₆ resonance. The U‐Pb systematics of Creston apatite reveals a Pb‐Pb age of 4,497.1 ± 3.7 Ma, and an upper intercept U‐Pb age of 4,496.7 ± 5.8 Ma (2σ), circa 70 Ma after formation of CAI, as found for other L chondrites. The K‐Ar (age ~4.3 Ga) and U,Th‐He (age ~1 Ga) chronometers were not reset at ~500 Ma, while the lower intercept U‐Pb age is poorly defined as 770 ± 320 Ma. So far, the three known L chondrites that impacted on orbits with semimajor axes a <2.0 AU all have high (>3 Ga) K‐Ar ages. This argues for a source of some of our L chondrites in the inner Main Belt. Not all L chondrites originate in a continuous population of Gefion family debris stretching across the 3:1 mean‐motion resonance.  相似文献   

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邱泽华  唐磊  周龙寿  阚宝祥 《大地测量与地球动力学》2009,29(1):1-5

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Ages of internal granitoids in the Southern Cross region,Yilgarn Craton,Western Australia,and their crustal evolution and tectonic implications     

Y. M. Qiu  N. J. McNaughton  D. I. Groves  H. J. Dalstra 《Australian Journal of Earth Sciences》2013,60(6):971-981

Southern Cross, where gold deposits are sited in narrow greenstone belts surrounding granitoid domes, was one of the earliest gold mining centres in Western Australia. SHRIMP U–Pb zircon and Pb‐isotope studies of the largest granitoid dome, the Ghooli Dome (80 × 40 km), provide important constraints on the crustal evolution and structural history of the central part of the Archaean Yilgarn Craton, Western Australia, which includes Southern Cross. The north‐northwest‐south‐southeast‐oriented ovoid Ghooli Dome has a broadly concentric foliation that is subhorizontal or gently dipping in its central parts and subvertical along its margins. Foliated granitoids in the dome are dated at ca 2724 ± 5 and 2688 ± 3 Ma using the SHRIMP U–Pb zircon and Pb–Pb isochron methods, respectively. These new data, together with the published SHRIMP U–Pb zircon age of 2691 ± 7 Ma at another locality, 20 km from the centre of the Koolyanobbing Shear Zone, suggest that the Ghooli Dome was emplaced at ca 2.72–2.69 Ga. Because the Ghooli Dome and the other domes, which are enveloped by narrow greenstone belts, are cut by the >650 km‐long and 6–15 km‐wide Koolyanobbing Shear Zone, the ca 2.69 Ga age is interpreted as the maximum age of the last major movement on this structure. The pre‐2.69 Ga history, if any, of the shear zone remains unknown. The shear zone is intruded by an undeformed porphyritic granitoid which has a SHRIMP U–Pb zircon age of 2656 ± 4 Ma. This age is, thus, the minimum age of major movement along this shear zone. Post‐gold mineralisation pegmatitic‐leucogranite from the Nevoria gold mine has a SHRIMP U–Pb zircon age of 2634 ± 4 Ma, with xenocrystic zircon cores of ca 2893 ± 6 Ma, constraining the minimum age of gold mineralisation there to ca 2.63 Ga. The ca 2.72–2.69 Ga granitoids also contain ca 2.98 and 2.78 Ga xenocrystic zircon cores, suggesting an extensive crustal prehistory for their source. Whereas there is a general temporal relationship between the periods of older (ca 3.0 Ga) and younger (ca 2.80 and 2.73 Ga) volcanism and the older (2.98, 2.78 and 2.72–2.69 Ga) granitoid intrusions, there is no known volcanism temporally associated with the 2.65–2.63 Ga granitoid intrusions in the Yilgarn Craton. Other heat sources and/or tectonic processes, required for the generation of these intrusions, are interpreted to be related to a lithospheric delamination event related to continental collision.  相似文献   

中印度洋脊Edmond区热液硫化物的形成——来自铅和硫同位素的约束     

王叶剑  韩喜球  金翔龙  初凤友  邱中炎 《吉林大学学报(地球科学版)》2012,(Z2):234-242,308

位于中印度洋脊23°52’S的Edmond热液区发现于2000年,属于典型的以玄武岩为宿主的活动热液区。首次测得了Edmond热液区9件硫化物的铅同位素和6件样品的硫同位素组成,结果表明:硫化物矿石的206Pb/204Pb为17.879～17.970,207Pb/204Pb为15.433～15.550,208Pb/204Pb为37.743～38.130。Pb-Pb图解表明,Edmond热液区硫化物的铅同位素数据与中印度洋脊玄武岩的铅同位素组成较一致,与印度洋沉积物和锰结壳相比具较低放射性成因铅的特征,说明硫化物中的铅主要来源于地幔(玄武岩),海水的贡献微弱。硫化物的δ34S为5.7‰～7.2‰,明显高于玄武岩的硫同位素组成(δ34S≈0‰),认为Edmond热液区硫化物中的硫除地幔的贡献外,海水中硫酸盐还原作用产生的硫的贡献可能超过30%。中印度洋脊Edmond热液区存在非常活跃的浅循环系统,可能是造成硫化物中硫同位素组成偏重的主要原因。  相似文献   

煤层气勘探开发从“以工程为主导”到“预测指导下的工程”之转变     

林建东  陈信平  胡超元  邱杰 《中国煤炭地质》2012,(3):48-52

通过多年的实践,从煤层气赋存特征、煤层气地质学理论出发,分析煤层气与天然气的根本区别。通过对天然气AVO理论的取舍,重建了煤层气AVO技术的岩石物理理论,保留了天然气AVO技术的地震波理论外壳,建立了煤层气AVO技术的地震波理论基础。将煤层气AVO技术的岩石物理基础和地震波理论基础应用于煤层气勘探开发实践中,在煤层气局部富集区预测实践中取得了较好的应用效果,实现煤层气勘探开发从“以工程为主导”到“预测指导下的工程”之转变。  相似文献   

辽宁盘锦新近系馆陶组地下热水分布特征及成因分析     

邱立军 《中国煤炭地质》2012,(4):42-46,51

辽宁盘锦新近系馆陶组地下热水埋藏较深,开发历史较早,但利用率较低。研究认为,该区地温场变化主要受地幔隆起相对程度控制;东西两侧幔隆带部位,地壳的厚度相对较薄,结晶岩基底埋藏浅,深部热能传导到储热层消耗能量少,地温及地温梯度值相对较高;中部幔凹带地温以中凸起最高,凹陷区相对较低。在地幔隆起的控制下,区内馆陶组地下水水温受储热层埋藏深度的影响,储热层的埋藏深度大,降低了热能向地表的散失速度,所以水温相对较高;反之,水温相对较低。地下水水温变化规律为：西部的谷坡区,受地下水径流影响,水温一般25℃～28℃,而凹陷区则为30℃～35℃;到中部隆起区水温升高到35℃～50℃;东部凹陷区为31℃～38℃,谷坡为29℃。深部上地幔幔源热源（岩浆热）构成本区生热层,经构造导热作用传输到储热层。最后指出,中央凸起区是该区馆陶组地下热水勘查开发的有利地区,重点开发应在温热水（I区）。  相似文献   

松辽平原古大湖演变及其平原的形成     

裘善文  王锡魁  张淑芹  廉毅  张振卿  朱金花 《第四纪研究》2012,32(5):1011-1021

北东向延伸的松辽平原位于中国东北地区中部,其西部与大兴安岭接壤,东部与长白山脉邻接.松辽平原主要是一个中新生代沉积盆地,其内沉积了巨厚的侏罗纪-白垩纪地层和420～ 530m厚的古近纪-新近纪地层,以及75～ 200m厚的第四纪地层.本文根据松辽平原北部500多个钻孔揭示的第四纪地层沉积序列和岩性,确定松辽平原第四纪早...  相似文献   

油源对比微量元素地球化学研究进展   总被引：2，自引：0，他引：2  

曹剑  吴明  王绪龙  胡文瑄  向宝力  孙平安  施春华  鲍海娟 《地球科学进展》2012,27(9):925-937

原油中的微量元素地球化学组成可以应用于油源对比,指标可以归纳为3类:①所含元素的聚类分析及其所反映的元素分布总体特征;②不同族、不同类型元素的组成,特别是过渡族金属元素;③稀土元素。但对于哪些微量元素可以应用于油源对比,哪些具有普遍意义,在不同地区是否具有适用性,影响其油源对比应用有效性的因素有哪些,主控因素是什么,仍然不甚清楚,由此导致很多方面的认识还不甚成熟,成功应用的实例相对常规的有机地球化学研究不多。原油中的微量元素主要来源于外部成油和运聚环境,在原油生成和运聚过程中,通过烃—水—岩之间的复杂有机—无机相互作用以金属卟啉螯合物、有机络合物或吸附态的形式聚集于原油中,并且沥青质是原油中微量元素的主要载体,元素组成在此过程中发生分异。此外,原油在自身形成与演化过程中也会发生元素组成的分异,影响因素包括油源母质类型、成熟度、次生变化等。在这些过程中,元素地球化学性质的不同会使原油中的元素组成出现差异,基本不发生/少发生变化的元素即可能是好的油源对比指标,这是应用微量元素进行油源对比的原理和理论基础。  相似文献   

来宾地区中晚二叠世之交烃源岩沉积的主控因素及大地构造背景          下载免费PDF全文

邱振  王清晨 《地质科学》2012,(4):1085-1098

通过对来宾地区蓬莱滩剖面和铁桥剖面中二叠统(茅口组)与上二叠统(合山组)TOC、古生产力(Ba/Al)以及保存条件(V/Cr、V/(V+Ni)等)等指标的研究,认为本区仅蓬莱滩剖面局部发育优质烃源岩(TOC平均可达3％),缺氧的盆地环境是本区烃源岩发育的主控因素。结合区域研究资料,认为黔桂盆地整体上不发育上二叠统烃源岩,可能与这一时期以峨眉山地幔柱为代表的区域性地壳隆升作用有关。  相似文献