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Cadomian metabasites of the Eastern Pyrenees revisited 东比利牛斯山脉卡多米亚变质岩重访
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-11-25 DOI: 10.1344/geologicaacta2022.20.17
N. Pujol-Solà, J. Casas, J. Proenza, I. Blanco-Quintero, E. Druguet, M. Liesa, M. J. Román-Alpiste, J. Álvaro
This study presents a new geochemical, petrological, and geochronological U–Pb dataset from Ediacaran metabasites of the Canigó and Cap de Creus massifs, Eastern Pyrenees. The rocks are composed of calcic amphibole + plagioclase + chlorite + epidote ± quartz plus titanite + apatite + ilmenite ± biotite ± rutile as accessory phases and show relict igneous textures. Peak pressure-temperature determinations share common conditions, ranging 452–482ºC and 5.2–7.7kbar. These intermediate P-T conditions suggest Barrovian-type metamorphism, most likely related to a collisional setting. The metabasites correspond to evolved basaltic rocks (Mg#<0.55) with moderate TiO2 content (up to 2.08wt.%) and relatively low Cr (43–416ppm). The rocks are moderately enriched in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) (average (La/Lu)n of 2.7) and the N-MORB normalized multi-element patterns show negative slopes, with prominent negative Nb anomalies ((Nb/La)NMORB=0.33–0.78). These variations are akin to island arc tholeiites generated in back-arc basins and to other metabasites described in the Eastern Pyrenees with a putative Ediacaran age, and they differ from the Ordovician tholeiitic metabasites from the Canigó massif, which derived from a contaminated E-MORB source. The positive ƐNd(T) values (0.82–3.05) of the studied metabasites preclude a notable contribution from an older continental crust. U-Pb dating (LA-ICP-MS) of one chlorite-rich schist sample in contact with the metabasites from the Canigó massif yielded a main peak at ca. 632Ma. We argue that the Cadomian metabasites from the Pyrenees formed during back-arc extension in the continental margin of Gondwana and were later affected by (probably early Variscan) medium-P metamorphism before the HT-LP metamorphism classically described in the Pyrenees.
本文介绍了东比利牛斯山脉Canigó和Cap de Creus地块埃迪卡拉纪变质岩中新的地球化学、岩石学和年代学U-Pb数据集。岩石由钙质角闪洞+斜长石+绿泥石+绿帘石+石英+钛矿+磷灰石+钛铁矿+黑云母±金红石为副相组成,呈残余火成岩结构。峰值压力-温度测定具有共同的条件,范围为452-482ºC和5.2-7.7kbar。这些中间的P-T条件表明巴罗维亚型变质作用,很可能与碰撞环境有关。变质岩为演化玄武岩(Mg#<0.55), TiO2含量适中(2.08wt.%), Cr含量较低(43 ~ 416ppm)。岩石轻稀土元素(LREE)相对重稀土元素(HREE)中等富集(平均(La/Lu)n为2.7),n - morb归一化多元素模式呈负斜率,负Nb异常显著((Nb/La)NMORB=0.33 ~ 0.78)。这些变化类似于弧后盆地中的岛弧拉斑岩和东比利牛斯山脉中描述的其他假定埃迪卡拉纪时代的变质岩,而不同于Canigó地块中来自受污染的E-MORB源的奥陶系拉斑岩变质岩。研究的变质岩的正ƐNd(T)值(0.82-3.05)排除了较老大陆地壳的显著贡献。对一个与Canigó地块中变质岩接触的富绿泥石片岩样品进行了LA-ICP-MS定年,得到了一个约632Ma的主峰。我们认为,来自比利牛斯山脉的卡多米尼亚变质岩形成于冈瓦纳大陆边缘弧后伸展时期,并在比利牛斯山脉经典描述的高温-低温变质作用之前受到(可能是早Variscan)中磷变质作用的影响。
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引用次数: 0
Cadomian/Pan-African consolidation of the Iberian Massif assessed by its detrital and inherited zircon populations: is the ~610Ma age peak a persistent Cadomian magmatic inheritance or the key to unravel its Pan-African basement? 通过碎屑和继承的锆石种群评估伊比利亚地块的卡多米亚/泛非固结:~610Ma时代的峰值是持续的卡多米亚岩浆继承,还是解开其泛非基底的关键?
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-11-23 DOI: 10.1344/geologicaacta2022.20.15
M. Chichorro, A. R. Solá, T. M. Bento dos Santos, João Lains Amaral, Lourenço Crispim
This work assessed the age distribution of Cadomian/Pan-African orogenic events (550-590 and 605-790Ma, respectively) in several zones of Iberian Massif by means of detrital and inherited zircon analysis compilation.
通过碎屑和继承锆石分析汇编,评价了伊比利亚地块若干带卡多米亚/泛非造山事件的年龄分布(分别为550 ~ 590 ma和605 ~ 790ma)。
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引用次数: 2
Shifts in the Ediacaran to Lower Ordovician sedimentary zircon provenances of Northwest Gondwana: the Pyrenean files 冈瓦纳大陆西北部埃迪卡拉纪-下奥陶世沉积锆石来源的变化:比利牛斯纪文件
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-10-21 DOI: 10.1344/geologicaacta2022.20.14
M. Padel, S. Clausen, M. Poujol, Jose Javier Alvaro Blasco
Detrital zircon grains from Cambrian–Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Anti-Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63–0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian–Tonian shift (ca. 1.25–0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central-Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions.
通过LA-ICPMS对比利牛斯山寒武系-下奥陶统砂岩和石英岩中的碎屑锆石颗粒进行了年代测定,以评估其物源。将由此产生的年龄分布与邻近边缘的其他可用数据集进行比较,如摩洛哥、伊比利亚半岛、法国南部和撒丁岛。Kolmogorov-Smirnov(K-S)检验和结晶年龄-沉积年龄(CA-DA)图用于比较锆石种群,估计它们与冈瓦纳大陆西北边缘弧/裂谷/漂移地球动力学演化的可能相关性。在Terreneuvian时代,锆石种群允许区分i)最西南边缘(Anti-Atlas Ossa Morena裂谷),主要受泛非洲和反大西洋来源的影响(约0.63–0.54),ii)记录撒哈拉元克拉通和阿拉伯-努比亚地盾影响的最东北边缘(撒丁岛),具有明显的斯堪的纳维亚-托尼亚期偏移(约1.25–0.85Ga)和iii)一个中间古地理样带,其中位于中伊比利亚、西阿斯图里亚莱昂和坎塔布里亚带、黑山和比利牛斯山,具有相似的人口和从反大西洋/泛非大陆到撒哈拉元克拉通/阿拉伯-努比亚地盾来源的时间上的渐进影响。锆石百分比种群的这种逐渐变化支持了基于气候敏感指标、寒武纪2古脊椎动物和微体化石组合的生物地理模式以及碳酸盐生产的横向相关事件的类似趋势,所有这些都指向了比利牛斯盆地的寒武纪背景,该盆地位于诺伊山(欧西坦地区)和冈瓦纳大陆西北部的撒丁岛边缘之间。比利牛斯山脉记录的Terreneuvian锆石模式从寒武纪2世到早奥陶世逐渐演化,反映了与裂谷主导条件有关的Panafrican弧和Cadomian弧的地球动力学演化。在芙蓉期和奥陶纪,锆石种群的相对百分比导致了更为广泛的年龄曲线,具有伸展环境的特征,并指向裂谷(被动边缘)条件。
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引用次数: 0
The chronology and rotational kinematics in the South-Eastern Jaca Basin (Southern Pyrenees): Las Bellostas section Jaca盆地东南部(比利牛斯山脉南部)的年表和旋转运动学:Las Bellostas剖面
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-09-23 DOI: 10.1344/geologicaacta2022.20.12
Emilio L. Pueyo, A. Rodríguez-Pintó, J. Serra-Kiel, A. Barnolas
Despite the large number of magnetostratigraphic studies in the South Pyrenean Basin aiming to calibrate the basin chronostratigraphy and the biostratigraphic scales, the South Eastern Jaca Basin remains unexplored from this perspective, and its relation with the Ainsa Basin is not fully understood. In this work we contribute with new magnetostratigraphic data from the 950m thick Las Bellostas section, located in the northern hinge of the Balzes anticline. Well-proven primary signal (positive fold test and two pseudo-antiparallel polarities) supported by numerous primary data in the surroundings allow us building a reliable local polarity sequence of eight magnetozones (from R1 to N4). Additionally, seven new biostratigraphic samples (Nummulites and Assilina) in the lower part of the section (marine environment) allows tightening the section to the Geomagnetic Polarity Time Scale (GPTS) and proposing a refined age model for the southeastern Jaca Basin. The section starts in the Boltaña Fm., of Cuisian age (Shallow Benthic Zone, SBZ11), is followed by a sedimentary gap from C22n to C20n as witnessed by biostratigraphic data (SBZ11 underneath the hiatus and SBZ16 just atop). The deltaic Sobrarbe Fm. can be tracked until the C19n (Late Lutetian). From this point (200m) until the top of the section (950m), at least, the entire C18n chron can be recognized within the molassic Campodarbe Fm. (C18n.2n-C18n.1r and C18n.1n) (Bartonian) equivalent to the West to the prodeltaic Arguis marls Fm. The Middle Cusian (SBZ11) to Middle Lutetian (SBZ15) stratigraphic hiatus is, in part, enhanced by the structural position at the hinge of the Balzes anticline. These new chronostratigraphic constraints help refining the W-E and N-S stratigraphic relationships in the eastern Jaca Basin and in the Ainsa Basin. This section also allows us to accurately refine the kinematics of the rotational activity in the eastern External Sierras. The important difference in magnetic declination along the section and neighboring paleomagnetic data from the Balzes anticline (from ≈70º clockwise at the base of the stratigraphic section to non-significant at the top) together with the new age model for the Eastern Jaca Basin help characterizing the rotational activity of the Balzes thrust sheet. The rotation took place between chrons C20r (Middle Lutetian; 45Ma) and C17 (Lower Priabonian 37-38Ma) in agreement to nearby structures (Boltaña, Picodel Aguila anticlines) but clearly diachronic to western ones (Santo Domingo anticline). Besides, the rotational activity seems to follow a linear and continuous pattern (velocity 9-11º/Ma, R: 0.83-0.96) in contrast to closer structures that show two distinct rotational velocities (i.e. Boltaña). These new data still let open the debate on the rotational kinematics along the South Pyrenean basal thrust.
尽管在南比利牛斯盆地进行了大量的磁地层学研究,旨在校准盆地年代地层学和生物地层学规模,但从这个角度来看,东南部的贾卡盆地仍未被勘探,其与安萨盆地的关系也未被完全了解。在这项工作中,我们提供了950米厚的Las Bellostas剖面的新磁地层学数据,该剖面位于Balzes背斜的北部铰链。周围环境中的大量原始数据支持的经过充分验证的原始信号(正折叠测试和两个伪反平行极性)使我们能够构建八个磁带(从R1到N4)的可靠局部极性序列。此外,该剖面下部(海洋环境)的七个新的生物地层样本(Nummulites和Assilina)使该剖面能够缩小到地磁极性时间尺度(GPTS),并提出了雅卡盆地东南部的精细年龄模型。该剖面始于Cuisian时代的Boltaña组(浅海底带,SBZ11),随后是从C22n到C20n的沉积间隙,如生物地层学数据所示(SBZ11位于裂孔下方,SBZ16位于顶部)。三角洲Sobrarbe组可以追踪到C19n(晚卢泰期)。从这一点(200米)到剖面顶部(950米),至少可以在相当于西部到前三角洲Arguis泥灰岩组的molassic Campodarbe组(C18n.2n-C18n.1r和C18n.1n)(Bartonian)内识别整个C18n时间段,巴尔茨背斜铰链处的构造位置增强了这一点。这些新的年代地层约束有助于完善Jaca盆地东部和Ainsa盆地的W-E和N-S地层关系。本节还使我们能够准确地完善外部Sierras东部旋转活动的运动学。沿剖面的磁偏角和Balzes背斜的邻近古地磁数据的重要差异(从地层剖面底部的顺时针≈70º到顶部的不显著),以及东部Jaca盆地的新年龄模型,有助于表征Balzes逆冲片的旋转活动。旋转发生在C20r(中卢泰阶;45Ma)和C17(下普里亚博阶37-38Ma)之间,与附近的构造(Boltaña、Picodel-Aguila背斜)一致,但与西部构造(圣多明各背斜)明显具有历时性。此外,旋转活动似乎遵循线性和连续的模式(速度9-11º/Ma,R:0.83-0.96),而较近的结构显示出两种不同的旋转速度(即Boltaña)。这些新数据仍然开启了关于南比利牛斯基底逆冲断层旋转运动学的争论。
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引用次数: 1
Geochemistry of Khandadharpahar-Thakuranipahar metabasites from the western Singhbhum Craton, eastern India: implications for subduction-zone tectonics and mantle-wedge metasomatism 印度东部Singhbhum克拉通西部Khandadharpahar Thakuranipahar变质玄武岩的地球化学:对俯冲带构造和地幔楔交代作用的影响
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-09-16 DOI: 10.1344/geologicaacta2022.20.11
R. Rajani
The identification of new rock types in the volcano-sedimentary sequences of the Singhbhum Craton has attractedmuch attention in recent years. The present study deals on newly identified Nb-Enriched Basalts (NEB) from theKhandadharpahar-Kadakala-Thakuranipahar (KKT) section, western Singhbhum Craton, which is comparablein composition to basalts-basaltic andesites and calk-alkaline in character. These metabasites have a porphyritictexture with phenocrysts of pyroxene and plagioclase, as well as a groundmass that has metamorphosed to thegreenschist facies. High Nb contents (7.5-22.8ppm) combined with high (Nb/Th)PM (0.28-0.59), (Nb/La)PM (0.40-0.69) and Nb/U (11.7-34.4) ratios, compared to arc basalts ((Nb/Th)PM= 0.10-1.19; (Nb/La)PMn 0.17-0.99, Nb/U<10), characterized them as NEB. Negative Nb, Zr, Hf and Ti anomalies, and Nb/Th vs La/Nb and Th/Nb vs. La/Sm relationships, collectively indicate typical arc volcanics. The available geochemical parameters suggest a genesisof KKT metabasites through i) slab melt migration from the downgoing oceanic crust, ii) low-degree melting ofthe garnet-bearing peridotite in the mantle wedge metasomatized by the slab melts, iii) slab melt - peridotiteinteraction triggering increasing Nb concentrations and iv) NEB generation in an arc-related environment. Thediscovery of KKT NEB sheds new information on Paleoproterozoic subduction-zone processes and crustal growthin the Singhbhum craton.
近年来,在Singhbhum火山口火山沉积序列中识别新的岩石类型引起了人们的广泛关注。本研究对Singhbhum克拉通西部Khandadharpahar Kadakala Thakuranipahar(KKT)剖面新发现的富铌玄武岩(NEB)进行了研究,其成分与玄武岩、玄武岩、安山岩和钙碱性玄武岩相当。这些变质玄武岩具有含辉石和斜长石斑晶的斑状结构,以及变质为绿片岩相的岩体。高Nb含量(7.5-22.8ppm)与高(Nb/Th)PM(0.28-0.59)、(Nb/La)PM(0.40-0.69)和Nb/U(11.7-34.4)比率相结合,与弧玄武岩((Nb/Th)PM=0.10-1.19)相比;(Nb/La)PMn 0.17-0.99,Nb/U<10),将其表征为NEB。Nb、Zr、Hf和Ti负异常,以及Nb/Th与La/Nb和Th/Nb与La/Sm的关系,共同表明了典型的弧火山岩。可用的地球化学参数表明,KKT变基岩的成因是通过i)来自下行海洋地壳的板状熔体迁移,ii)由板状熔体交代的地幔楔中含石榴石的橄榄岩的低温熔融,iii)板状熔体-橄榄岩的相互作用触发Nb浓度的增加,以及iv)在与电弧相关的环境中产生NEB。KKT NEB的发现为Singhbhum克拉通古元古代俯冲带过程和地壳生长提供了新的信息。
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引用次数: 0
Organic-walled tentaculids of Late Devonian (Frasnian) deposits of the Appalachian and Michigan Basins, Laurussia (NY, MI, OH) Laurussia (NY, MI, OH)阿巴拉契亚和密歇根盆地晚泥盆世(frasian)沉积物的有机壁触手
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-09-15 DOI: 10.1344/geologicaacta2022.20.10
K. C. Meehan, J. Boyle
This is the first report of organic-walled tentaculid remains from Givetian through Frasnian age deposits of the Michigan and Appalachian Basins in western Laurussia. This adds to the geographic scope of similar finds that have been described from the Frasnian through the Famennian in eastern Laurussia. However, those previous specimens were retrieved through palynological preparations and more closely resemble sheath structures rather than the full forms found herein, which were retrieved through complete maceration with ammonium surfactants.
这是第一份关于洛俄罗斯西部密歇根盆地和阿巴拉契亚盆地从吉维期到Frasnian时代沉积物的有机壁帐篷遗迹的报告。这增加了类似发现的地理范围,这些发现已被描述为从劳俄罗斯东部的Franian到Famennian。然而,这些先前的标本是通过孢粉学制备获得的,更接近于鞘结构,而不是本文中发现的完整形式,后者是通过用铵表面活性剂完全浸渍获得的。
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引用次数: 0
Characterization of the shallow subsurface structure across the Carrascoy Fault System (SE Iberian Peninsula) using P-wave tomography and Multichannel Analysis of Surface Waves 使用P波层析成像和表面波多通道分析表征Carrascoy断层系统(伊比利亚半岛东南部)的浅层地下结构
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-09-08 DOI: 10.1344/geologicaacta2022.20.9
H. Handoyo, I. DeFelipe, R. Martín-Banda, J. García-Mayordomo, D. Martí, J. J. Martínez-Díaz, J. Insua-Arévalo, Teresa Teixidó, J. Alcalde, I. Palomeras, R. Carbonell
The seismicity in the SE Iberian Peninsula is distributed parallel to the coast in a well-developed strike-slip fracture system known as the Eastern Betic Shear Zone (EBSZ). This work focuses on the characterization of the shallow subsurface structure of the Algezares-Casas Nuevas Fault, within the Carrascoy Fault System of the EBSZ. The Carrascoy Fault borders the Guadalentín Depression to the south, which is a densely populated area with extensive agricultural activity. Therefore, this faults system represents a seismic hazard with significant social and economic implications. We have constructed two velocity-depth models based on P-wave tomography and Multichannel Analysis of Surface Waves (MASW) acquired from seismic reflection data. The resulting velocity models have allowed us to interpret the first ~250m depth and have revealed: i) the thickness of the critical zone; ii) the geometry of the Algezares-Casas Nuevas Fault; iii) the depth of the Messinian/Tortonian contact and iv) the presence of blind thrusts and damage zones under the Guadalentín Depression. Our results have also helped us to estimate an apparent vertical slip rate of 0.66±0.06m/ky for the Algezares-Casas Nuevas Fault since 209.1±6.2ka. Our results provide a methodological and backflow protocol to study the shallow subsurface of active faults, complementing previous geological models based on paleoseismological trenches, and can be used to improve the seismic hazard assessment of tectonically active regions around the world.
伊比利亚半岛东南部的地震活动平行于海岸分布在一个发育良好的走滑断裂系统中,该系统被称为东Betic剪切带(EBSZ)。本工作的重点是EBSZ Carrascoy断层系统内Algezares Casas Nuevas断层浅层地下结构的特征。Carrascoy断层以南与Guadalentín凹陷接壤,这是一个人口稠密、农业活动广泛的地区。因此,该断层系统代表了一种具有重大社会和经济意义的地震灾害。基于地震反射数据的P波层析成像和多通道表面波分析,我们建立了两个速度-深度模型。由此产生的速度模型使我们能够解释最初~250m的深度,并揭示了:i)临界区的厚度;ii)Algezares Casas Nuevas断层的几何形状;iii)Messinian/Tortonian接触的深度,以及iv)Guadalentín凹陷下盲冲断层和破坏带的存在。我们的研究结果还帮助我们估计了自209.1±6.2ka以来Algezares Casas Nuevas断层的表观垂直滑动速率为0.66±0.06m/ky,并可用于改进世界各地构造活动区的地震危险性评估。
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引用次数: 2
Petrology and geochemistry of Plio-Quaternary high-Nb basalts from Shahr-e-Babak area:Insights into post-collision magmatic processes in the Kerman Cenozoic Magmatic Arc Shahr-e-Babak地区上第四纪高铌玄武岩的岩石学和地球化学:对Kerman新生代岩浆弧碰撞后岩浆过程的认识
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-08-31 DOI: 10.1344/geologicaacta2022.20.8
Sakine Moradi, T. Khaksar, Asma Nazarinia, Amjad Hussain
Post-collision Pliocene-Quaternary basaltic rocks outcrop in the Kerman Cenozoic Magmatic Arc (KCMA) to the northwest and east of Shahr-e-Babak city. These porphyritic and vesicular basaltic rocks are composed essentially of clinopyroxene, olivine, and plagioclase. These basalts display alkaline affinity and negative Ta, Zr, Rb anomaly, but slightly negative Nb anomaly, relative to elements with similar compatibility, and positive Ba, K, Sr anomaly, suggesting their magma source related to subduction-accretion with implication of subducted slab derived components to the source. In the primitive mantle and chondrite normalized diagrams, these rocks show trace elements (except depletion in Nb, Ta) and Rare Earth Element (REE) patterns similar to the Ocean Island Basalts (OIB) and share trace and major element characteristics similar to High-Nb Basalts (HNBs). Geochemical analyses for major and trace elements suggest that the Shahr-e-Babak HNBs have undergone insignificant crustal contamination and minor olivine + Fe-Ti oxide ±clinopyroxene fractional crystallization. These HNBs derived from a partial melting (~5%) of garnet-peridotite mantle wedge, which have already metasomatized by overlying sediments, fluids, and adakitic (slab-derived) melts as major metasomatic agents in post-collision setting in the KCMA. We conclude that asthenospheric upwelling arising from slab break-off followed by the roll-back of subducting Neotethys slab also triggered metasomatized peridotite mantle wedge and caused its partial melting in the subduction zone.
碰撞后的上新世-第四纪玄武岩在Shahr-e-Babak市西北和东部的克尔曼新生代岩浆弧(KCMA)中露头。这些斑状和泡状玄武岩主要由斜辉石、橄榄石和斜长石组成。这些玄武岩显示出碱性亲和性和负Ta、Zr、Rb异常,但相对于具有相似相容性的元素,显示出轻微的负Nb异常,以及正Ba、K、Sr异常,表明其岩浆源与俯冲吸积有关,并暗示俯冲板衍生成分与岩浆源有关。在原始地幔和球粒陨石归一化图中,这些岩石显示出类似于海岛玄武岩(OIB)的微量元素(Nb、Ta贫化除外)和稀土元素(REE)模式,并具有类似于高Nb玄武岩(HNBs)的微量和主元素特征。主要元素和微量元素的地球化学分析表明,Shahr-e-Babak HNBs经历了轻微的地壳污染和少量的橄榄石+Fe-Ti氧化物±单斜辉石分级结晶。这些HNBs来源于石榴石-橄榄岩-地幔楔的部分熔融(~5%),在KCMA碰撞后环境中,石榴石-橄榄石-地幔楔已经被上覆沉积物、流体和adakitic(板状)熔体交代为主要交代剂。我们的结论是,板块断裂引起的软流圈上升流伴随着俯冲的新特提斯板块的回滚,也触发了交代橄榄岩地幔楔,并导致其在俯冲带部分熔融。
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引用次数: 0
Modelling of the LTDE-SD radionuclide diffusion experiment in crystalline rock at the Äspö Hard Rock Laboratory (Sweden) 瑞典硬石实验室晶体岩石中LTE-SD放射性核素扩散实验建模
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-07-28 DOI: 10.1344/geologicaacta2022.20.7
J. Soler, S. Meng, L. Moreno, I. Neretnieks, Longcheng Liu, P. Kekäläinen, M. Hokr, J. Říha, A. Vetešník, D. Reimitz, Jakub Višňák, D. Vopálka, Klaus-Peter Kröhn, Y. Tachi, Tsuyoshi Ito, U. Svensson, A. Iraola, P. Trinchero, M. Voutilainen, G. Deissmann, D. Bosbach, D. Park, S. Ji, L. Gvoždík, Martin Milický, M. Polak, B. Gylling, B. Lanyon
This study shows a comparison and analysis of results from a modelling exercise concerning a field experiment involving the transport and retention of different radionuclide tracers in crystalline rock. This exercise was performed within the Swedish Nuclear Fuel and Waste Management Company (SKB) Task Force on Modelling of Groundwater Flow and Transport of Solutes (Task Force GWFTS).Task 9B of the Task Force GWFTS was the second subtask within Task 9 and focused on the modelling of experimental results from the Long Term Sorption Diffusion Experiment in situ tracer test. The test had been performed at a depth of about 410m in the Äspö Hard Rock Laboratory. Synthetic groundwater containing a cocktail of radionuclide tracers was circulated for 198 days on the natural surface of a fracture and in a narrow slim hole drilled in unaltered rock matrix. Overcoring of the rock after the end of the test allowed for the measurement of tracer distribution profiles in the rock from the fracture surface (A cores) and also from the slim hole (D cores). The measured tracer activities in the rock samples showed long profiles (several cm) for non- or weakly-sorbing tracers (Cl-36, Na-22), but also for many of the more strongly-sorbing radionuclides. The understanding of this unexpected feature was one of the main motivations for this modelling exercise. However, re-evaluation and revision of the data during the course of Task 9B provided evidence that the anomalous long tails at low activities for strongly sorbing tracers were artefacts due to cross-contamination during rock sample preparation. A few data points remained for Cs-137, Ba-133, Ni-63 and Cd-109, but most measurements at long distances from the tracer source (>10mm) were now below the reported detection limits.Ten different modelling teams provided results for this exercise, using different concepts and codes. The tracers that were finally considered were Na-22, Cl-36, Co-57, Ni-63, Ba-133, Cs-137, Cd-109, Ra-226 and Np-237. Three main types of models were used: i) analytical solutions to the transport-retention equations, ii) continuum-porous-medium numerical models, and iii) microstructure-based models accounting for small-scale heterogeneity (i.e. mineral grains, porosities and/or microfracture distributions) and potential centimetre-scale fractures. The modelling by the different teams led to some important conclusions, concerning for instance the presence of a disturbed zone (a few mm in thickness) next to the fracture surface and to the wall of the slim hole and the role of micro-fractures and cm-scale fractures in the transport of weakly sorbing tracers. These conclusions could be reached after the re-evaluation and revision of the experimental data (tracer profiles in the rock) and the analysis of the different sets of model results provided by the different teams.
本研究对结晶岩中不同放射性核素示踪剂迁移和保留的现场实验建模结果进行了比较和分析。这项工作是在瑞典核燃料和废物管理公司(SKB)地下水流动和溶质输送建模工作队(GWFTS工作队)内进行的。GWFTS工作组的任务9B是任务9中的第二个子任务,重点是对长期吸附扩散实验原位示踪剂测试的实验结果进行建模。该测试是在约410米深的硬石实验室进行的。含有放射性核素示踪剂混合物的合成地下水在裂缝的自然表面和在未改变的岩石基质中钻出的狭窄小孔中循环198天。试验结束后对岩石进行过钻孔,可以测量破裂面(A岩芯)和细孔(D岩芯)岩石中的示踪剂分布剖面。岩石样品中测得的示踪剂活性显示,非或弱吸收示踪剂(Cl-36、Na-22)以及许多强吸收放射性核素的示踪剂活性都很长(几厘米)。对这一意外特征的理解是此次建模活动的主要动机之一。然而,在任务9B过程中对数据的重新评估和修订提供了证据,证明强吸收示踪剂低活性的异常长尾是由于岩石样品制备过程中的交叉污染造成的伪影。Cs-137、Ba-133、Ni-63和Cd-109的一些数据点仍然存在,但在距离示踪剂源较远(>10mm)的大多数测量值现在都低于报告的检测限值。10个不同的建模团队使用不同的概念和代码为本次演习提供了结果。最终考虑的示踪剂是Na-22、Cl-36、Co-57、Ni-63、Ba-133、Cs-137、Cd-109、Ra-226和Np-237。使用了三种主要类型的模型:i)输运-滞留方程的分析解,ii)连续多孔介质数值模型,以及iii)基于微观结构的模型,考虑小规模非均质性(即矿物颗粒、孔隙率和/或微裂缝分布)和潜在厘米级裂缝。不同团队的建模得出了一些重要结论,例如,在裂缝表面和细孔壁附近存在扰动带(厚度为几毫米),以及微裂缝和厘米级裂缝在弱吸收示踪剂传输中的作用。这些结论可以在对实验数据(岩石中的示踪剂剖面)进行重新评估和修订,并对不同团队提供的不同模型结果进行分析后得出。
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引用次数: 3
The early middle Eocene transition at the Esera valley 埃塞拉山谷早、中始新世的过渡
IF 1.5 4区 地球科学 Q2 GEOLOGY Pub Date : 2022-07-12 DOI: 10.1344/geologicaacta2022.20.6
A. Barnolas, A. Rodríguez-Pintó, G. Bernaola, Emilio L. Pueyo, J. Tosquella, P. Arbués, R. Scholger
An integrated study including magnetostratigraphy, larger benthic foraminifera and calcareous nannofossil biostratigraphy is presented herein. This work was performed in shallow marine siliciclastics rich in larger foraminifera, around the Ypresian/Lutetian boundary in the Ésera valley (South-Central Pyrenees). Although the calcareous nannofossil content in the studied interval is low, not allowing a precise Y/L boundary to be recognised, the taxa found are enough to support the chronostratigraphic attribution.Data obtained in the Ésera valley section has improved the knowledge of larger benthic foraminifera (Nummulitesand Assilina) distribution through chron C21. SBZ 11 to SBZ 12 transition took place at the lowermost C21r, as shown in previous works. SBZ 12 assemblages extend into C21n, where the SBZ 12 to SBZ 13 boundary occurs. These data, obtained in shallow marine siliciclastic facies, with in situ fauna, results in a shift of the SBZ 12/SBZ 13 boundary to the Lower Lutetian, younger than previously believed. Accordingly, the Ypresian/Lutetian boundary occurs in SBZ 12.
本文对磁地层学、大型底栖有孔虫和钙质纳米化石生物地层学进行了综合研究。这项工作是在Ésera山谷(比利牛斯山脉中南部)Ypresian/Lutetian边界附近富含大型有孔虫的浅海硅塑料中进行的。虽然研究层段的钙质纳米化石含量较低,无法识别精确的Y/L边界,但所发现的分类群足以支持年代地层归属。通过C21时间,在Ésera流域剖面获得的数据提高了对大型底栖有孔虫(nummulites和Assilina)分布的认识。sbz11到sbz12的转变发生在最低的C21r,如之前的工作所示。sbz12组合延伸到C21n,在那里出现了sbz12和sbz13的边界。这些数据是在浅海硅岩相中获得的,具有原位动物群,结果表明sbz12 / sbz13边界向下鲁特梯的移动,比以前认为的要早。因此,Ypresian/Lutetian边界出现在sbz12。
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引用次数: 3
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