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Xenotime reveals Caledonian hydrothermal overprint on Neoproterozoic Cu mineralization, East Greenland Xenotime揭示东格陵兰新元古代铜矿化上的加里东期热液叠加
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-22 DOI: 10.1144/jgs2022-141
H. Olierook, Kelsey Crook, Penelope Sinclair, D. Fougerouse, Cilva Joseph, C. Kirkland, A. Kennedy, Hao Gao, N. Evans, B. McDonald, Raiza R. Quintero, Anusha Shantha Kumara, Graeme Cameron, Ben Walsh, M. Roberts, B. McInnes
Constraining the age of many types of ore deposits remains challenging due to the lack of radiogenic isotopes incorporated into common ore-forming minerals. The timing of pre-Caledonian-hosted Cu mineralization along the entire ∼1200 km-long East Greenland Caledonides remains virtually unknown, hampering our knowledge of ore deposit timing and genesis in a frontier exploration region. Here, automated mineral analysis of a series of nodular, disseminated and vein-hosted Cu- ± Pb-mineralized metasedimentary rocks in central East Greenland reveals detrital zircon and hydrothermal xenotime, both amenable to U-Pb geochronology. Detrital zircon geochronology of a co-deposited quartzite reveals an age distribution highly similar to the Cryogenian (∼700 Ma) upper Eleanore Bay Supergroup. Hydrothermal xenotime U-Pb analyses adjacent to nodular and disseminated chalcocite across three proximal samples have variable amounts of common Pb that together yield a well-defined single discordia with a lower concordia intercept of 438 ± 13 Ma (2σ). This age is within uncertainty of the onset of Caledonian regional metamorphism and granitoid production and clearly post-dates deposition of the upper Eleanore Bay Supergroup by several hundred Myr. Considering a published chalcocite Pb-Pb isochron age of 680 ± 65 Ma, the hydrothermal xenotime U-Pb ages imply that Caledonian-driven fluid activity, sourced from metamorphic reactions or from granitoids, remobilized diagenetic Cu and Pb mineralization. Chalcocite Pb-Pb isotopes show that dissolved and reprecipitated portions are volumetrically minor, radiogenic and Pb-poor, implying that fluids stripped most of the Pb from the system. Thus, it is likely that remobilization was localized on the grain scale, although some Cu and Pb was transported away from diagenetic sites, perhaps into veins. Whilst Caledonian metamorphism and granitoid emplacement is widespread in central East Greenland, the full extent of their roles in upgrading Cu mineralization remains to be ascertained. Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle Supplementary material: https://doi.org/10.6084/m9.figshare.c.6675384
由于缺乏纳入常见成矿矿物的放射性同位素,限制许多类型矿床的年龄仍然具有挑战性。沿整个约1200公里长的东格陵兰加里东群岛,前加里东期主控铜矿化的时间几乎未知,这阻碍了我们对前沿勘探区矿床时间和成因的了解。在这里,对格陵兰岛中东部一系列结节状、浸染状和脉状Cu-±Pb矿化变质沉积岩的自动矿物分析揭示了碎屑锆石和热液捕虏体,两者都符合U-Pb地质年代学。共沉积石英岩的碎屑锆石地质年代学揭示了与成冰纪(~700Ma)上埃莉诺湾超群高度相似的年龄分布。在三个近端样品中,与结节状和浸染状辉铜矿相邻的热液捕虏体时间U-Pb分析具有不同量的常见Pb,这些Pb共同产生了一个明确的单一不整合,其较低的协心截距为438±13Ma(2σ)。这一年龄在加里东期区域变质作用和花岗岩类生产开始的不确定性范围内,显然是埃莉诺湾上超群沉积的晚期几百Myr。考虑到已公布的辉铜矿Pb-Pb等时线年龄为680±65Ma,热液捕虏期U-Pb年龄表明,加里东期驱动的流体活动源于变质反应或花岗岩类,再活化成岩铜和铅矿化。辉铜矿Pb-Pb同位素表明,溶解和再沉淀的部分体积较小,属于放射成因,Pb含量低,这意味着流体从系统中剥离了大部分Pb。因此,尽管一些Cu和Pb从成岩位点迁移出去,可能进入矿脉,但再活化很可能局限于颗粒尺度。虽然加里东期变质作用和花岗岩类侵位在格陵兰岛中东部广泛存在,但它们在铜矿化升级中的全部作用仍有待确定。主题收藏:本文是Caledonian Wilson周期收藏的一部分,可在以下网站上获得:https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle补充材料:https://doi.org/10.6084/m9.figshare.c.6675384
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引用次数: 1
3D seismic reflection evidence for lower crustal intrusions beneath the Faroe-Shetland Basin, NE Atlantic Margin 北大西洋边缘法罗-设得兰盆地下地壳侵入体的三维地震反射证据
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-19 DOI: 10.1144/jgs2022-172
Lucinda K. Layfield, N. Schofield, D. Watson, S. Holford, D. Jolley, Ben A. Kilhams, D. Muirhead, A. Roberts, A. Alvey, Alex Ellwood, M. Widdowson
Lower crustal intrusion is considered a common process along volcanic or magma-rich passive margins, including the NE Atlantic Margin, where it is considered to have occurred during phases of Paleogene magmatism, prior to and during continental break-up between NW Europe and Greenland. Evidence of Paleogene magmatism is prevalent throughout the sub-basins of the Faroe-Shetland Basin (FSB) as extensive lava flows and pervasive suites of igneous intrusions. However, in contrast to other areas located along the NE Atlantic Margin, no lower crustal reflectivity indicative of lower crustal intrusions has been documented beneath the FSB. The nearest documentation of lower crustal reflectivity and interpretation of lower crustal intrusions to the FSB is NW of the Fugloy Ridge, beneath the Norwegian Basin of the Faroese sector. Despite this, the addition of magma within the lower crust and/or at the Mohorovičić discontinuity is thought to have played a role regarding Paleogene uplift and the subsequent deposition of Paleocene-Eocene sequences. Advances in sub-basalt seismic acquisition and processing have made significant improvements in facilitating the imaging of deep crustal structures along the NE Atlantic Margin. This study uses broadband 3D seismic reflection data to map a series of deep ( c. 14 to 20 km depth) high-amplitude reflections which may represent igneous intrusions within the lower crust beneath the central-northern Corona Ridge. We estimate that the cumulative thicknesses of the reflections may be over 5 km in places, which is consistent with published values of magmatic underplating within the region based on geochemical and petrological data. We also estimate that the total volume of lower crustal high-amplitude reflections within the 3D dataset may be over 2000 km 3 . 2D gravity modelling of a seismic line located along the central-northern Corona Ridge supports the interpretation of lower crustal intrusions beneath the central-northern Corona Ridge. This study provides evidence of a potential mechanism for Paleogene uplift within the region. If uplift occurred as a result of lower crustal intrusions emplaced within the crust during the Paleogene, based on previous work, we estimate that around 300 m of uplift may have been generated within the Corona Ridge area.
下地壳侵入被认为是沿火山或富含岩浆的被动边缘的一个常见过程,包括东北大西洋边缘,在那里,它被认为发生在古近纪岩浆活动阶段,在欧洲西北部和格陵兰岛之间的大陆破裂之前和期间。古近系岩浆作用的证据在整个法罗-设得兰盆地(FSB)的子盆地中普遍存在,表现为广泛的熔岩流和普遍的火成岩侵入岩。然而,与位于东北大西洋边缘的其他地区相比,FSB下方没有记录到表明下部地壳侵入的较低地壳反射率。与FSB最近的低地壳反射率和低地壳侵入体解释文件是位于法罗群岛地区挪威盆地下方的Fugloy山脊西北部。尽管如此,下地壳和/或Mohorovičić不连续面内的岩浆添加被认为在古近系隆起和随后的古新世-始新世序列沉积方面发挥了作用。亚玄武岩地震采集和处理的进展在促进东北大西洋边缘地壳深部结构成像方面取得了重大进展。这项研究使用宽带3D地震反射数据绘制了一系列深(约14至20公里深)高振幅反射图,这些反射图可能代表科罗纳山脊中北部下地壳内的火成侵入体。我们估计,反射的累积厚度在某些地方可能超过5公里,这与根据地球化学和岩石学数据公布的该地区岩浆底侵值一致。我们还估计,3D数据集中的低地壳高振幅反射的总体积可能超过2000 km 3。位于中北部科罗纳山脊沿线的地震线的2D重力建模支持对中北部科罗纳山脊下的下地壳侵入体的解释。这项研究为该地区古近系隆起的潜在机制提供了证据。根据先前的工作,如果隆起是由于古近纪地壳内侵位的下地壳侵入而发生的,我们估计科罗纳山脊地区可能产生了约300米的隆起。
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引用次数: 0
Multiple stages of continental rifting in Eastern Peninsular Malaysia: New insights from Jurassic–Cretaceous granitoids 马来西亚半岛东部大陆裂谷作用的多个阶段:侏罗纪-白垩纪花岗岩的新见解
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-19 DOI: 10.1144/jgs2023-025
Xin Qian, Tianxing Bai, Yongqi Yu, K. A. Mustapha, Thomas C. Sheldrick, Chengshi Gan, Yuejun Wang
Mesozoic granitoids in Peninsular Malaysia provide crucial information on the temporal-spatial relationship between the Tethyan and Paleo-Pacific domains. This paper presents new ages and geochemical data for the newly identified Jurassic–Cretaceous granites and meta-granites in East Malaya. These granitoids can be divided into three groups. Group 1 high-K calc-alkaline granites and granodiorites (171–162 Ma) have variable ε Nd (t) values of −7.4–+0.5, zircon ε Hf (t) values of −7.4–+8.6, and high initial ratios for 206 Pb/ 204 Pb (20.04–20.65), 207 Pb/ 204 Pb (15.73–15.7) and 208 Pb/ 204 Pb (39.80–40.20). These samples were probably derived from the metasedimentary rocks with a juvenile mafic component. Despite Group 2 granite porphyries (∼131 Ma) with A-type affinities and Group 3 granitic gneisses (∼130 Ma) with I-type affinities share similar ε Nd (t) values (−5.5–−7.2), zircon ε Hf (t) values (−10.1–+6.5), and initial ratios for 206 Pb/ 204 Pb (18.81–19.02), 207 Pb/ 204 Pb (15.71–15.77) and 208 Pb/ 204 Pb (38.95–39.95). Although Group 2 and 3 samples were derived from an “ancient” meta-mafic source region, Group 2 has evidence for the involvement of a juvenile mafic component. All these granitoids are akin to the Permian–Triassic igneous rocks in East Malaya. The Jurassic–Cretaceous igneous rocks in Eastern Peninsular Malaysia were formed during multiple stages of continental rifting in response to pulses of the Paleo-Pacific slab rollback rather than from Tethyan evolutionary processes. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change Supplementary material: https://doi.org/10.6084/m9.figshare.c.6689085
马来西亚半岛的中生代花岗质岩石为特提斯和古太平洋地区之间的时空关系提供了重要信息。本文介绍了新发现的东马来亚侏罗纪-白垩纪花岗岩和变质花岗岩的新时代和地球化学数据。这些花岗岩类可分为三类。第1组高钾钙碱性花岗岩和花岗闪长岩(171–162 Ma)的εNd(t)值为−7.4–+0.5,锆石εHf(t。尽管具有A型亲和力的第2组花岗斑岩(~131Ma)和具有I型亲和力的第一组花岗片麻岩(~130Ma)具有相似的εNd(t)值(−5.5–−7.2)、锆石εHf(t)(−10.1–+6.5)和206 Pb/204 Pb的初始比值(18.81–19.02),207 Pb/204 Pb(15.71–15.77)和208 Pb/204 Pb38.95–39.95。所有这些花岗质岩石都类似于东马来亚的二叠纪-三叠纪火成岩。马来西亚半岛东部的侏罗纪-白垩纪火成岩是在大陆裂谷的多个阶段形成的,这是对古太平洋板块回滚的响应,而不是特提斯演化过程。主题收藏:本文是中新生代构造、景观和气候变化收藏的一部分,可在以下网站获取:https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change补充材料:https://doi.org/10.6084/m9.figshare.c.6689085
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引用次数: 1
Silurian to Early Devonian tectonic evolution of the southeastern Qilian Orogen inferred from zircon U–Pb dating and geochemistry of intrusive rocks 根据锆石U-Pb测年和侵入岩地球化学推断祁连造山带东南部志留纪—早泥盆世构造演化
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-19 DOI: 10.1144/jgs2022-162
Xiyao Li, San-zhong Li, Sheng‐yao Yu, Yong‐jiang Liu, Zhen Qin, Zeng-Bao Huang, Qing Lu
Early to mid-Paleozoic tectono-thermal events in the Qilian Orogen developed during the closure of the Proto-Tethys Ocean and the convergence of microcontinents in the periphery of East Gondwana. In this paper, we present geochronological, geochemical, and Sr-Nd-Hf isotopic data for the granitoid rocks and mafic dykes in southeastern Qilian Orogen. The Liwan (440 Ma), Shixia (434 Ma), and Huchuan (429 Ma) granitoid rocks have metaluminous to weakly peraluminous features, with whole-rock ε Nd (t) values of 1.1 to 1.6, -4.2 to -4.4, and -2.6 to 1.1, and zircon ε Hf (t) values of 0 to 8.9, -6.6 to 1.6, and -4.6 to 2.2, respectively. Geochemical data suggest that the Liwan, Shixia, and Huchuan granitoids are derived from partial melting of the Proterozoic basement with an addition of juvenile material, a felsic crustal basement, and a mafic crustal material, respectively. The Zhangjiayuan mafic dykes (403 Ma) are high-K to shoshonitic with whole-rock ε Nd (t) (-1.1 to -0.9) and zircon ε Hf (t) values (-0.9 to 13.3), derived from an enriched lithospheric mantle. We suggest that these Silurian–Early Devonian intrusive rocks were formed via a complex series of events involving arc-related subduction followed by slab-tearing to post-collisional processes during the Silurian and subsequent lithospheric extension in the Early Devonian. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6693575
祁连造山带早古生代至中古生代构造热事件是在原特提斯洋闭合和冈瓦纳大陆外围微大陆汇聚期间发展起来的。本文介绍了祁连造山带东南部花岗质岩石和镁铁质岩脉的地质年代、地球化学和Sr-Nd-Hf同位素数据。荔湾(440 Ma)、石峡(434 Ma)和湖川(429 Ma)花岗岩具有金属发光至弱过发光特征,全岩εNd(t)值分别为1.1至1.6、-4.2至-4.4和-2.6至1.1,锆石εHf(t)分别为0至8.9、-6.6至1.6和-4.6至2.2。地球化学数据表明,荔湾、石峡和壶川花岗岩类分别源于元古界基底的部分熔融,并添加了新生物质、长英质地壳基底和镁铁质地壳物质。张家源镁铁质岩脉(403Ma)为高钾-钠玄岩,全岩εNd(t)(-1.1至-0.9)和锆石εHf(t)值(-0.9至13.3)源自富集的岩石圈地幔。我们认为,这些志留系-早泥盆系侵入岩是通过一系列复杂的事件形成的,这些事件涉及志留系期间与弧相关的俯冲,然后是板块撕裂到碰撞后过程,以及随后的早泥盆世岩石圈伸展。补充材料:https://doi.org/10.6084/m9.figshare.c.6693575
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引用次数: 0
Magmatic arc evolution during the tectonic closure of the Rocas Verdes basin: insights from Cretaceous-earliest Paleocene intrusive rocks of Navarino Island (55°S), Fuegian Andes Rocas-Verdes盆地构造闭合期间的岩浆弧演化:来自富安地斯山脉纳瓦里诺岛(55°S)白垩纪最早古新世侵入岩的见解
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-08 DOI: 10.1144/jgs2022-163
R. Velásquez, J. Bastías, E. Salazar, F. Poblete, M. G. Guillot, D. Chew, M. Peña, Felipe Tapia, Adán Ramirez, Foteini Drakou
Navarino Island is located in the southernmost part of the Fuegian Andes, south of the Beagle Channel. It geological record documents the complex tectonic history of Tierra del Fuego that includes the opening and closure of the Rocas Verdes basin, Cordillera arc collision and subsequent subduction processes. The geology of the island is mostly comprised of the Cretaceous Yahgán Formation, a marine meta-sedimentary sequence, which is intruded by diverse plutons that are mostly exposed on the northwestern tip of the island. We herein present a new dataset that shows the presence of three Cretaceous-earliest Paleocene magmatic suites of active margin magmatism emplaced during the early stage of the Fuegian Andes, which are referred to as (i) the Dientes de Navarino Microdioritic Sills, a suite of pre-tectonic microdioritic sills that formed during ∼101-97 Ma; (ii) the Castores Plutonic Complex, a series of pre- to syn-tectonic gabbroic to tonalitic plutons emplaced during ∼90-87 Ma and (iii) the Samantha Monzonites, a suite of isolated monzonitic to monzodioritic post-tectonic plutons that formed at ∼66-65 Ma. These distinct magmatic episodes are recognised by field observations, geological mapping, petrography and whole-rock geochemistry integrated with amphibole and biotite 40 Ar/ 39 Ar and U-Pb zircon LA-ICP-MS geochronology. The geochemical compositions of these rocks are consistent with a continental arc setting that formed during the interval ∼101-65 Ma. While the three pulses spatially overlap in Navarino Island, the arc magmatism shows a migration (or expansion) throughout the Late Cretaceous. The locus of the arc then migrates at ∼68-66 Ma towards the southwest. We suggest that this trench-ward migration at ∼68-66 Ma may be associated with a change in the subduction angle. The three Cretaceous- earliest Paleocene plutonic pulses recorded in Navarino Island formed during the early stages of development of the Fuegian Andes, and are pre-, syn-and post-tectonic with respect to a major compressional event caused by the collision and obduction of the back-arc Rocas Verdes oceanic floor. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6675416
纳瓦里诺岛位于安第斯山脉最南端,比格尔海峡以南。它的地质记录记录了火地岛复杂的构造历史,包括罗卡斯韦德斯盆地的开放和关闭,科迪勒拉弧碰撞和随后的俯冲过程。岛上的地质主要由白垩纪Yahgán组组成,这是一个海相元沉积序列,被各种各样的岩体侵入,这些岩体大多暴露在岛的西北端。在此,我们提出了一个新的数据集,显示了三个白垩纪-最早的古新世活跃边缘岩浆作用的岩浆套,它们位于Fuegian Andes早期,被称为(i) Dientes de Navarino微闪长岩基,一套形成于~ 101-97 Ma的构造前微闪长岩基;(ii) Castores深裂杂岩,一系列形成于~ 90-87 Ma的前-同构造辉长岩-重质岩体;(iii) Samantha二长岩,一套形成于~ 66-65 Ma的孤立二长-二黄道带后构造岩体。通过野外观测、地质填图、岩石学和全岩地球化学,结合角闪洞、黑云母40 Ar/ 39 Ar和U-Pb锆石LA-ICP-MS年代学,识别了这些不同的岩浆期。这些岩石的地球化学成分与形成于~ 101-65 Ma区间的大陆弧背景一致。当三个脉冲在纳瓦里诺岛空间上重叠时,弧岩浆活动在整个晚白垩纪表现出迁移(或扩张)。弧的轨迹随后在~ 68-66 Ma向西南方向移动。我们认为,这种在~ 68 ~ 66 Ma的向海沟迁移可能与俯冲角的变化有关。在纳瓦里诺岛记录的三个白垩纪-最早的古新世深冲脉冲形成于Fuegian Andes发育的早期阶段,是由弧后罗卡斯佛迪斯洋底碰撞和逆冲引起的一次主要挤压事件的前、同、后构造期。补充资料:https://doi.org/10.6084/m9.figshare.c.6675416
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引用次数: 0
Early Neoproterozoic magmatism and Caledonian metamorphism recorded by the Mårma Terrane, Seve Nappe Complex, northern Swedish Caledonides 瑞典喀里多尼亚北部Seve推覆杂岩mamatrma地体记录的新元古代早期岩浆作用与加里东期变质作用
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-06 DOI: 10.1144/jgs2022-092
R. Callegari, K. Kośmińska, C. Barnes, I. Klonowska, A. Barker, S. Rousku, E. Nääs, E. Kooijman, P. Witt-Nilsson, J. Majka
Petrology, geochronology, and bulk rock chemistry are combined to investigate the early Neoproterozoic magmatism and Cambrian-Ordovician metamorphism in the northern Swedish Caledonides. This includes several lithologies of the Mårma terrane in the Seve Nappe Complex exposed in the Kebnekaise region. U–Pb zircon geochronology yielded crystallization ages of 835 ± 8 Ma for a mylonitic orthogneiss, 864 ± 3 Ma for the Vistas Granite and 840 ± 7 Ma for a related granitic dyke. While a gabbro and granodiorite intrusions gave U–Pb zircon crystallization ages of 856 ± 3 Ma and 850 ± 1 Ma, respectively. U–Pb monazite dating of the mylonitic orthogneiss gave an upper intercept age of 841 ± 7 Ma and a lower intercept age of 443 ± 20 Ma. Pressure-temperature estimates derived for the mylonitic orthogneiss reveal metamorphic peak-pressure and peak-temperature of 10.5–11.75 kbar and 550–610 °C and 7.4–8.1 kbar at 615–675 ℃, respectively. Metamorphic pressure-temperature estimates for the Vistas Granite yield 6.5–7.5 kbar at 600–625 ℃. Whole rock chemistry coupled with U–Pb geochronology indicate that bimodal magmatism was related to attempted rifting of Rodinia between 870-840 Ma. Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle Supplementary material: https://doi.org/10.6084/m9.figshare.c.6675075
将岩石学、地质年代学和大块岩石化学相结合,研究了瑞典喀里多尼亚山脉北部新元古代早期岩浆作用和寒武纪-奥陶纪变质作用。这包括Kebnekaise地区暴露的Seve Nappe杂岩中Mårma地体的几个岩性。U–Pb锆石地质年代学得出的糜棱岩正片麻岩结晶年龄为835±8 Ma,Vistas花岗岩结晶年龄为864±3 Ma,相关花岗岩脉结晶年龄为840±7 Ma。辉长岩和花岗闪长岩侵入体的U–Pb锆石结晶年龄分别为856±3 Ma和850±1 Ma。糜棱岩正片麻岩的U–Pb独居石测年给出了841±7Ma的上截距年龄和443±20Ma的下截距年龄。推导出的糜棱岩正片麻岩压力-温度估计值显示,在615–675℃下,变质峰值压力和峰值温度分别为10.5–11.75kbar、550–610°C和7.4–8.1kbar。Vistas花岗岩在600–625℃时的变质压力-温度估计值为6.5–7.5 kbar。全岩化学与U–Pb地质年代学相结合表明,双峰岩浆作用与870-840 Ma之间的罗迪尼亚裂谷作用有关。专题收藏:本文是Caledonian Wilson旋回收藏的一部分,可在:https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle补充材料:https://doi.org/10.6084/m9.figshare.c.6675075
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引用次数: 0
Tectonic evolution of a Palaeoproterozoic diffuse cryptic suture zone in northern Fennoscandia and the correlation of northern Fennoscandia and southern Greenland 芬诺斯堪的纳维亚北部古元古代扩散隐缝合带的构造演化及芬诺斯坎迪亚北部与格陵兰南部的对比
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-06 DOI: 10.1144/jgs2023-007
R. Lahtinen, J. Köykkä, M. Kurhila
The boundary between the Karelia and Norrbotten continental blocks in Fennoscandia is a diffuse cryptic suture zone recording ca. 200 Ma of tectono-metamorphic evolution between 1.92 and 1.72 Ga. Syn-collisional deposition at 1.92–1.91 Ga was followed by post-collisional deposition at 1.88–1.87 Ga and 1.85–1.84 Ga. The post-collision structural overprint in the suture starts with sinistral movements due to aulacogen inversion (D2), east of the suture. Late-D2 and D orocline extensional stages are followed by NE-vergent basin inversion (D3) of <1.88 Ga rocks and transpressional dextral shear in the suture zone. Nearly orthogonal D4 and D5 deformation events overprint earlier fabrics at ca. 1.83 Ga and ca. 1.78 Ga, respectively. The youngest (D6, ca. 1.73 Ga) structures include sinistral brittle-ductile movements. Northern Fennoscandia and southern Greenland are linked by coeval continent–continent collisions (D1, 1.92–1.89 Ga). The D orocline stage (ca. 1.87 Ga), responsible for oroclinal buckling in central Fennoscandia, is conceivably related to W-directed subduction and subsequent regional shortening in western Greenland. The D3–D4 events in Fennoscandia are comparable to and D5–D6 correlate well with tectonic events in the suture zone in the eastern Nagssugtoqidian orogen in Greenland. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6675191
芬诺斯坎迪亚的卡累利阿陆块和北北陆块之间的边界是一个弥漫的隐缝带,记录了1.92 - 1.72 Ga之间约200 Ma的构造变质演化。在1.92 ~ 1.91 Ga发生同碰撞沉积,在1.88 ~ 1.87 Ga和1.85 ~ 1.84 Ga发生碰撞后沉积。缝合带上的碰撞后构造叠印始于缝合带上以东的断陷槽反转(D2)的左旋运动。晚d2期和D期造山斜伸展期之后是<1.88 Ga的北东向盆地反转(D3)和缝合带内的右向横切作用。近正交的D4和D5变形事件分别在约1.83 Ga和约1.78 Ga覆盖了早期织物。最年轻的构造(D6,约1.73 Ga)包括左旋脆性-韧性运动。芬诺斯坎迪亚北部和格陵兰岛南部由同时期大陆-大陆碰撞连接(D1, 1.92-1.89 Ga)。D造斜阶段(约1.87 Ga)是造成芬诺斯坎迪亚中部造斜弯曲的主要原因,可能与西格陵兰岛的西向俯冲和随后的区域缩短有关。Fennoscandia的D3-D4事件与格陵兰纳格苏木托起甸造山带东部缝合带的构造事件相当,D5-D6事件具有良好的相关性。补充资料:https://doi.org/10.6084/m9.figshare.c.6675191
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引用次数: 1
Predation Bias of Ordovician Predators on Trilobites 奥陶系捕食者对三叶虫的捕食偏好
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-02 DOI: 10.1144/jgs2023-019
Ruiwen Zong, Ruoying Fan, Y. Gong
Although prey selection has been commonly documented in extant animals, evidence of prey selection in deep time is rare by comparison. Here, we collected 147 broken sclerites of trilobites, almost of which caused by lethal predation, from the Upper Ordovician in NW China. The damages were mainly distributed in three larger trilobites ( Platyptychopyge , Birmanites and Ordosaspis ), and larger-bodied trilobites were more vulnerable to predation. One plausible explanation is that Late Ordovician predators in this area preferred larger trilobites, because the greater nutrients and energy provided by larger prey, and larger prey require less effort to capture because they are less capable of escaping from predation compared with smaller prey, which can more easily hide or escape. Another lower possibility is survivor bias due to smaller prey being completely eaten up. Moreover, the large-eyed trilobite Nileus , which has a similar size and morphology to Ordosaspis , had a theoretical preying rate less than 1/20 of that of Ordosaspis , indicating that the eye is an important sensory organ in trilobites. The increased predation pressure may have also contributed to the increased eye diversity and visual system resolution of trilobites since the Ordovician. Thematic collection: This article is part of the Chemical Evolution of the Mid-Paleozoic Earth System and Biotic Response collection available at: https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system Supplementary material: https://doi.org/10.6084/m9.figshare.c.6670609
尽管在现存动物中普遍记录了猎物的选择,但相比之下,在深层次选择猎物的证据却很少。在这里,我们收集了147个三叶虫的破裂硬骨,其中几乎是由致命的捕食引起的,来自中国西北的上奥陶世。损伤主要分布在三种较大的三叶虫中(Platyptypyrige、Birmanites和Ordospis),体型较大的三叶虫更容易被捕食。一个合理的解释是,该地区的晚奥陶世捕食者更喜欢较大的三叶虫,因为较大的猎物提供了更多的营养和能量,而较大的猎物需要更少的努力来捕捉,因为与更容易隐藏或逃跑的较小猎物相比,它们逃离捕食的能力较弱。另一种较低的可能性是由于较小的猎物被完全吃掉而产生的幸存者偏见。此外,大眼三叶虫Nileus的大小和形态与Ordospis相似,理论捕食率不到Ordospi的1/20,表明眼睛是三叶虫的重要感觉器官。自奥陶纪以来,捕食压力的增加也可能导致三叶虫的眼睛多样性和视觉系统分辨率的增加。专题集:本文是中古生代地球系统的化学演化和生物反应集的一部分,可在以下网站获取:https://www.lyellcollection.org/topic/collections/chemical-evolution-of-the-mid-paleozoic-earth-system补充材料:https://doi.org/10.6084/m9.figshare.c.6670609
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引用次数: 0
Implications of sulfur mineralogy and consequences of pyrite oxidation for ground engineering 硫矿物学和黄铁矿氧化对地面工程的影响
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-06-02 DOI: 10.1144/jgs2022-101
M. A. Czerewko, J. Cripps
Aggressive ground conditions and physical deterioration of ground and engineering materials are attributed to a wide range of factors but in the UK a high proportion of occurrences in the engineering environment result from the presence of sulfur minerals, particularly pyrite which is unstable in oxidising and damp atmospheric weathering conditions. The oxidation reactions are complex in that the rate - and the products - depend on the crystalline form and grain size of the pyrite as well as the host mineralogy, rock fabric and environmental conditions, including exposure to weathering action brought about by engineering works. Therefore, to prevent any negative impacts on engineering design and construction, the possibility of changes in the potential for pyrite oxidation during and after construction need to be considered. The aim of this paper is to review the implications of sulfur minerals, especially of pyrite oxidation, with reference to engineering situations in which pyrite oxidation may have a significant negative impact. Changes in the potential for oxidation because of ground engineering works and strategies for avoiding problems are also considered. Thematic collection: This article is part of the Sulfur in the Earth system collection available at: https://www.lyellcollection.org/topic/collections/sulfur-in-the-earth-system
恶劣的地面条件以及地面和工程材料的物理劣化可归因于多种因素,但在英国,工程环境中出现的大部分情况是由于硫矿物的存在,特别是黄铁矿,它在氧化和潮湿的大气风化条件下不稳定。氧化反应是复杂的,其速率和产物取决于黄铁矿的结晶形式和粒度,以及宿主矿物学、岩石结构和环境条件,包括工程带来的风化作用。因此,为了防止对工程设计和施工产生负面影响,需要考虑施工期间和施工后黄铁矿氧化电位变化的可能性。本文的目的是回顾硫矿物,特别是黄铁矿氧化的意义,并参考黄铁矿氧化可能产生重大负面影响的工程情况。还考虑了由于地面工程和避免问题的策略而引起的氧化电位的变化。专题合集:本文是地球系统中的硫合集的一部分,可在:https://www.lyellcollection.org/topic/collections/sulfur-in-the-earth-system上获得
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引用次数: 0
The Burmese Jade Mines belt: origins of jadeitites, serpentinites and ophiolitic peridotites and gabbros 缅甸玉石矿带:翡翠、蛇纹岩、蛇绿橄榄岩和辉长岩的起源
IF 2.7 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2023-05-23 DOI: 10.1144/jgs2023-004
M. Searle, R. Palin, N. Gardiner, K. Htun, J. Wade
Ophiolitic peridotites in Burma (Myanmar) occur along three major tectonic zones, the Kaleymyo–Nagaland suture, Indo-Burman ranges, the Jade Mines belt, and the Tagaung–Mytkyina belt. These belts all show harzburgite–lherzolite–dunite peridotites, but the Hpakan-Taw Maw region (Jade Mines belt) hosts jadeitites including pure jadeite, mawsitsit (chromium-rich jadeite) kosmochlore (chromium-rich clinopyroxene), and albitite. High Na and Al contents of jadeitites require either very unusual Al-rich, Si-poor protoliths, or extensive fluid metasomatism, or both. The Hpakan jadeitites formed by Na-, Al-, (and Si) metasomatic alteration of pyroxenite–wehrlite intrusions into harzburgite–dunite, from widespread fluid alteration. Fluids could have been derived from a mid-Jurassic intermediate pressure subduction event during ophiolite formation and emplacement. In the Indawgyi Lake area, normal ophiolitic peridotites, including harzburgite and dunite with pyroxenite veins, have not been jadeitised. Gabbros related to the Jade Mines ophiolite gave a U-Pb zircon age of 169.71±1.3 Ma (MSWD 2.2), similar timing to the Myitkyina ophiolite (173 Ma) to the east, suggesting that the ophiolite belts were originally continuous. The jade ‘boulders’ in the Uru conglomerate beds at Hpakan have also resulted from normal in-situ serpentinisation weathering processes, followed by limited fluvial mass transport processes along the Uru river. Supplementary material: https://doi.org/10.6084/m9.figshare.c.6655269
缅甸的蛇绿岩橄榄岩分布在三个主要构造带,即Kaleymyo–Nagaland缝合带、Indo-Burman山脉、Jade Mines带和Tagaung–Mytkyina带。这些带都显示出方辉橄榄岩-二辉橄榄岩–纯橄榄岩,但帕干-陶莫地区(玉石矿带)有翡翠,包括纯翡翠、mawsitsit(富铬翡翠)kosmochlore(富铬斜辉石)和钠长石。翡翠的高Na和Al含量需要非常不寻常的富Al、贫Si原岩,或广泛的流体交代作用,或两者兼而有之。Hpakan硬玉岩是由辉石岩-辉石岩侵入体的Na、Al、(和Si)交代蚀变形成的,由广泛的流体蚀变形成。流体可能来源于蛇绿岩形成和侵位期间的侏罗纪中期中压俯冲事件。在Indawgyi湖地区,正常的蛇绿橄榄岩,包括方辉橄榄岩和带辉石岩脉的纯橄榄岩,尚未被翡翠化。与Jade Mines蛇绿岩有关的Gabbros给出了169.71±1.3 Ma(MSWD 2.2)的U-Pb锆石年龄,与东部密支那蛇绿岩(173 Ma)的时间相似,表明蛇绿岩带最初是连续的。Hpakan的Uru砾岩层中的玉石“巨石”也是正常的原地蛇纹石化风化过程的结果,随后是沿着Uru河的有限河流质量输送过程。补充材料:https://doi.org/10.6084/m9.figshare.c.6655269
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引用次数: 0
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Journal of the Geological Society
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