Wei Jian, Jingwen Mao, Bernd Lehmann, Nigel J. Cook, Jiankang Li, Shiwei Song, Lei Zhu
Gold precipitation in hydrothermal systems is traditionally attributed to supersaturation of gold due to decreasing gold complex stability triggered by changes in physicochemical conditions of the ore fluid. However, ultrahigh-grade gold veins in orogenic (shear zone related) gold deposits can contain kilograms per tonne of gold or more, in marked contrast to the typically very low gold concentrations (tens of parts per billion) in fluid. The gold mineral assemblage is commonly restricted to native gold and/or Au-(Ag)-tellurides and occurs in micro-fractures of sheared quartz veins. Textural and compositional characterization of such assemblages, coupled with hydrothermal diamond anvil cell experiments and heating-freezing experiments, provides evidence for an alternative ultrahigh-grade gold enrichment mechanism via growth of polymetallic melt droplets induced by quartz fracturing. We propose that polymetallic melt droplets of Au-Ag-Te-Bi−rich composition form through adsorption-reduction of metal complexes on fractured quartz surfaces, where surface silanol groups and hydrogen serve as reductants. The melt droplets subsequently grow by catalyzing reduction of metal complexes and absorbing metals from fluids percolating in the fractured quartz network. The mobile and reactive polymetallic melt droplets can repeatedly react with the fluid on protracted quartz fracturing and efficiently continue to scavenge gold from multiple pulses of gold-undersaturated ore fluids.
{"title":"Hyper-enrichment of gold via quartz fracturing and growth of polymetallic melt droplets","authors":"Wei Jian, Jingwen Mao, Bernd Lehmann, Nigel J. Cook, Jiankang Li, Shiwei Song, Lei Zhu","doi":"10.1130/g51875.1","DOIUrl":"https://doi.org/10.1130/g51875.1","url":null,"abstract":"Gold precipitation in hydrothermal systems is traditionally attributed to supersaturation of gold due to decreasing gold complex stability triggered by changes in physicochemical conditions of the ore fluid. However, ultrahigh-grade gold veins in orogenic (shear zone related) gold deposits can contain kilograms per tonne of gold or more, in marked contrast to the typically very low gold concentrations (tens of parts per billion) in fluid. The gold mineral assemblage is commonly restricted to native gold and/or Au-(Ag)-tellurides and occurs in micro-fractures of sheared quartz veins. Textural and compositional characterization of such assemblages, coupled with hydrothermal diamond anvil cell experiments and heating-freezing experiments, provides evidence for an alternative ultrahigh-grade gold enrichment mechanism via growth of polymetallic melt droplets induced by quartz fracturing. We propose that polymetallic melt droplets of Au-Ag-Te-Bi−rich composition form through adsorption-reduction of metal complexes on fractured quartz surfaces, where surface silanol groups and hydrogen serve as reductants. The melt droplets subsequently grow by catalyzing reduction of metal complexes and absorbing metals from fluids percolating in the fractured quartz network. The mobile and reactive polymetallic melt droplets can repeatedly react with the fluid on protracted quartz fracturing and efficiently continue to scavenge gold from multiple pulses of gold-undersaturated ore fluids.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140422003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mengyu Xu, W. Xiao, Kai Liu, B. Wan, Ross N. Mitchell, G. Rosenbaum, Hao Wang
Subduction erosion at convergent margins is a leading mechanism for the destruction (recycling and reworking) of continental crust. But because of the lack of direct evidence, it is not straightforward to identify erosive events and their intensities in fossil subduction zones. The Heilongjiang accretionary complex in northeastern China was formed during the early Mesozoic subduction of the Paleo-Pacific Ocean. We investigated amphibolites from this accretionary complex, whose protoliths (based on whole-rock trace elements and Sr-Nd-Hf isotopes) were mafic continental arc magmatic rocks (255−249 Ma; zircon core U-Pb ages) from the upper plate. Phase equilibria modeling constrained by mineral geochemistry indicates that the amphibolites and their wall rocks were first heated to low granulite facies (750−800 °C, ∼7 kbar) at 251−244 Ma (zircon rim U-Pb ages) and then cooled to ∼700 °C with increasing pressure (8−9 kbar) before 213−187 Ma (titanite and apatite U-Pb ages). To explain the occurrence of the lower arc crustal lithologies in the accretionary complex and their metamorphic history, we propose that the subducting plate strongly eroded the forearc crust, allowing the plate interface to advance landward and scrape the amphibolites and wall rocks formed under the old arc, which finally were exhumed along the subduction channel and became components of the complex. The case study exemplifies direct petrological evidence of strong subduction erosion occurring in an ancient orogen, thus implying that consumption of the entire forearc crust could occur within only ∼50 m.y.
{"title":"Subduction erosion revealed by exhumed lower arc crustal rocks in an accretionary complex, northeastern China","authors":"Mengyu Xu, W. Xiao, Kai Liu, B. Wan, Ross N. Mitchell, G. Rosenbaum, Hao Wang","doi":"10.1130/g51803.1","DOIUrl":"https://doi.org/10.1130/g51803.1","url":null,"abstract":"Subduction erosion at convergent margins is a leading mechanism for the destruction (recycling and reworking) of continental crust. But because of the lack of direct evidence, it is not straightforward to identify erosive events and their intensities in fossil subduction zones. The Heilongjiang accretionary complex in northeastern China was formed during the early Mesozoic subduction of the Paleo-Pacific Ocean. We investigated amphibolites from this accretionary complex, whose protoliths (based on whole-rock trace elements and Sr-Nd-Hf isotopes) were mafic continental arc magmatic rocks (255−249 Ma; zircon core U-Pb ages) from the upper plate. Phase equilibria modeling constrained by mineral geochemistry indicates that the amphibolites and their wall rocks were first heated to low granulite facies (750−800 °C, ∼7 kbar) at 251−244 Ma (zircon rim U-Pb ages) and then cooled to ∼700 °C with increasing pressure (8−9 kbar) before 213−187 Ma (titanite and apatite U-Pb ages). To explain the occurrence of the lower arc crustal lithologies in the accretionary complex and their metamorphic history, we propose that the subducting plate strongly eroded the forearc crust, allowing the plate interface to advance landward and scrape the amphibolites and wall rocks formed under the old arc, which finally were exhumed along the subduction channel and became components of the complex. The case study exemplifies direct petrological evidence of strong subduction erosion occurring in an ancient orogen, thus implying that consumption of the entire forearc crust could occur within only ∼50 m.y.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140418126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qingbao Duan, Å. Fagereng, Jianye Chen, Thomas Blenkinsop
The slip style of continental midcrustal shear zones plays a crucial role in determining the seismogenic potential of faults, but it remains poorly understood because geological observations that can be directly tied to seismic behavior are scarce. We describe frictional-viscous shear zones in the Red River fault, China, which consists of two segments with distinct seismic behaviors and fluid availabilities. The northern segment hosts moderate to large earthquakes, and midcrustal fault slip is localized into mylonitized pseudotachylyte-bearing layers where dynamically recrystallized quartz records flow stresses exceeding 100 MPa and accelerated viscous creep. The southern segment is dominantly aseismic but active microseimically. Fault slip is accommodated in several mylonitized cataclasite layers, comprising interconnected biotite and intervening fractured clasts, with evidence for pervasive dissolution-precipitation creep. Microstructures, paleopiezometry, and microphysical modeling suggest transient aseismic slip in response to increased strain rates during viscous creep at <50 MPa. We interpret that along-strike variations in fluid environment control fault slip styles and seismic behaviors. The dry and strong northern segment is capable of nucleating large earthquakes, while greater fluid availability in the southern segment activates dissolution-precipitation creep at low driving stresses, which limits interseismic elastic strain accumulation at frictional-viscous transition depths. In this model, compaction-driven fluid pressurization and dilatant hardening are invoked to explain the aseismic slip transients in the southern segment.
{"title":"Fluid environment controls along-strike variation in slip style: Midcrustal geological signatures from the Red River fault, China","authors":"Qingbao Duan, Å. Fagereng, Jianye Chen, Thomas Blenkinsop","doi":"10.1130/g51865.1","DOIUrl":"https://doi.org/10.1130/g51865.1","url":null,"abstract":"The slip style of continental midcrustal shear zones plays a crucial role in determining the seismogenic potential of faults, but it remains poorly understood because geological observations that can be directly tied to seismic behavior are scarce. We describe frictional-viscous shear zones in the Red River fault, China, which consists of two segments with distinct seismic behaviors and fluid availabilities. The northern segment hosts moderate to large earthquakes, and midcrustal fault slip is localized into mylonitized pseudotachylyte-bearing layers where dynamically recrystallized quartz records flow stresses exceeding 100 MPa and accelerated viscous creep. The southern segment is dominantly aseismic but active microseimically. Fault slip is accommodated in several mylonitized cataclasite layers, comprising interconnected biotite and intervening fractured clasts, with evidence for pervasive dissolution-precipitation creep. Microstructures, paleopiezometry, and microphysical modeling suggest transient aseismic slip in response to increased strain rates during viscous creep at <50 MPa. We interpret that along-strike variations in fluid environment control fault slip styles and seismic behaviors. The dry and strong northern segment is capable of nucleating large earthquakes, while greater fluid availability in the southern segment activates dissolution-precipitation creep at low driving stresses, which limits interseismic elastic strain accumulation at frictional-viscous transition depths. In this model, compaction-driven fluid pressurization and dilatant hardening are invoked to explain the aseismic slip transients in the southern segment.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140418865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
New mapping of the Barberton Greenstone Belt in South Africa shows that the central part is a pseudo-stratigraphy made of shallow-water and deep-water siliciclastic and volcanic slide blocks, with individual blocks ranging in size from tens of meters to >10 km in length. The outcrop pattern and scale are remarkably similar to those of large-scale Miocene to recent submarine landslides in New Zealand along the active Hikurangi subduction zone that are periodically triggered by earthquakes on the subduction megathrust, providing evidence for megathrust earthquakes in the Paleoarchean.
{"title":"Large-scale submarine landslides in the Barberton Greenstone Belt, southern Africa—Evidence for subduction and great earthquakes in the Paleoarchean","authors":"Simon Lamb, C. D. de Ronde","doi":"10.1130/g51997.1","DOIUrl":"https://doi.org/10.1130/g51997.1","url":null,"abstract":"New mapping of the Barberton Greenstone Belt in South Africa shows that the central part is a pseudo-stratigraphy made of shallow-water and deep-water siliciclastic and volcanic slide blocks, with individual blocks ranging in size from tens of meters to >10 km in length. The outcrop pattern and scale are remarkably similar to those of large-scale Miocene to recent submarine landslides in New Zealand along the active Hikurangi subduction zone that are periodically triggered by earthquakes on the subduction megathrust, providing evidence for megathrust earthquakes in the Paleoarchean.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140427522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zeyang Zhu, Jing Wu, G. Chu, P. Rioual, Jiaxin Lu, Luo Wang, Jiaqi Liu
The last deglaciation is considered a key period for exploring the underlying dynamics of temperature changes because it was characterized by multiple millennial-scale abrupt climatic events. However, the limited number of quantitative temperature records in Northeast (NE) China covering the last deglaciation hampers a complete understanding of the mechanisms and processes behind the temperature changes that occurred in that region. Here, we present a quantitative reconstruction of summer temperature over the last deglaciation based on bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) analyzed from the sediment sequence of Lake Kielguo, a small volcanic lake in NE China. The results show that summer temperature was lowest during the interval ca. 20−18.2 calibrated (cal.) k.y. B.P. with a value of ∼11.1 °C and increased by ∼1.9 °C during Heinrich Stadial 1 (HS1) and by ∼2.7 °C during the transition to the Bølling-Allerød (B-A). The summer temperatures during the B-A warm interval and Younger Dryas cold interval were ∼14.1 °C and ∼12.0 °C, respectively. The summer temperature record from the Lake Kielguo sediment sequence indicates that summer warming dominated the climate change state during HS1 in East Asia, which is different from the cooling pattern controlled by winter temperatures in the North Atlantic and Greenland realms. This distinction can be explained by weakened winter cooling signals triggered by the collapse of Atlantic Meridional Overturning Circulation when these signals propagated to East Asia, and increased summer temperature warming controlled by orbital and greenhouse gases during HS1 in East Asia.
{"title":"Summer warming during Heinrich Stadial 1 in Northeast China","authors":"Zeyang Zhu, Jing Wu, G. Chu, P. Rioual, Jiaxin Lu, Luo Wang, Jiaqi Liu","doi":"10.1130/g51881.1","DOIUrl":"https://doi.org/10.1130/g51881.1","url":null,"abstract":"The last deglaciation is considered a key period for exploring the underlying dynamics of temperature changes because it was characterized by multiple millennial-scale abrupt climatic events. However, the limited number of quantitative temperature records in Northeast (NE) China covering the last deglaciation hampers a complete understanding of the mechanisms and processes behind the temperature changes that occurred in that region. Here, we present a quantitative reconstruction of summer temperature over the last deglaciation based on bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) analyzed from the sediment sequence of Lake Kielguo, a small volcanic lake in NE China. The results show that summer temperature was lowest during the interval ca. 20−18.2 calibrated (cal.) k.y. B.P. with a value of ∼11.1 °C and increased by ∼1.9 °C during Heinrich Stadial 1 (HS1) and by ∼2.7 °C during the transition to the Bølling-Allerød (B-A). The summer temperatures during the B-A warm interval and Younger Dryas cold interval were ∼14.1 °C and ∼12.0 °C, respectively. The summer temperature record from the Lake Kielguo sediment sequence indicates that summer warming dominated the climate change state during HS1 in East Asia, which is different from the cooling pattern controlled by winter temperatures in the North Atlantic and Greenland realms. This distinction can be explained by weakened winter cooling signals triggered by the collapse of Atlantic Meridional Overturning Circulation when these signals propagated to East Asia, and increased summer temperature warming controlled by orbital and greenhouse gases during HS1 in East Asia.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140429803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Maestrelli, Federico Sani, Derek Keir, C. Pagli, Alessandro La Rosa, A. Muluneh, Sascha Brune, G. Corti
Rift-Rift-Rift triple junctions are regions where three plates interact, generating complex networks of variably oriented faults. While the geometry of the fault networks is easily constrained from their surface expression, what remains unclear is how the kinematics of faults and their interactions vary spatially, and how these relate to the unusual crustal motions that result from three plates diverging from each other. The Afar depression lies at the triple junction between the African, Arabian, and Somalian plates (in the Horn of Africa), where the unique combination of observational data from structural mapping, seismicity, and Global Navigation Satellite System (GNSS) allows us to understand the link between fault kinematics and plate motions. We complement these observations with an analog model to gain insights into how the patterns and directions of faults relate to overall plate motions. A key finding in both the model and nature is that some adjacent normal faults form at high angles and generate T-shaped structures. These purely normal faults are synchronously active, which means that the extension direction varies ∼90° locally. These kinematic contrasts in our model and in nature occur despite the relatively smooth pattern of overall surface motions. The results indicate that normal faults interacting at high angles to form the T-shaped structures can evolve synchronously within a stress field that varies gently in magnitude but dramatically in orientation over a few kilometers.
断裂-断裂-断裂三重交界处是三个板块相互作用的区域，产生了复杂的方向可变的断层网络。虽然断层网络的几何形状很容易从其地表表现中得到约束，但仍不清楚的是断层的运动学及其相互作用在空间上是如何变化的，以及这些变化与三个板块相互分离所产生的异常地壳运动之间的关系。阿法尔凹陷位于非洲板块、阿拉伯板块和索马里板块（位于非洲之角）的三重交界处，在这里，结构测绘、地震和全球导航卫星系统（GNSS）等观测数据的独特组合使我们能够了解断层运动学与板块运动之间的联系。我们用一个模拟模型来补充这些观测数据，以深入了解断层的形态和方向与整个板块运动之间的关系。模型和自然界的一个关键发现是，一些相邻的正断层以高角度形成，并产生 T 形结构。这些纯正的正断层是同步活动的，这意味着延伸方向在局部变化了90°。尽管整体地表运动模式相对平滑，但我们的模型和自然界中的这些运动对比还是出现了。结果表明，以高角度相互作用形成 T 形结构的正断层可以在几千米范围内的应力场中同步演化，应力场的大小变化平缓，但方向变化剧烈。
{"title":"Reconciling plate motion and faulting at a rift-rift-rift triple junction","authors":"D. Maestrelli, Federico Sani, Derek Keir, C. Pagli, Alessandro La Rosa, A. Muluneh, Sascha Brune, G. Corti","doi":"10.1130/g51909.1","DOIUrl":"https://doi.org/10.1130/g51909.1","url":null,"abstract":"Rift-Rift-Rift triple junctions are regions where three plates interact, generating complex networks of variably oriented faults. While the geometry of the fault networks is easily constrained from their surface expression, what remains unclear is how the kinematics of faults and their interactions vary spatially, and how these relate to the unusual crustal motions that result from three plates diverging from each other. The Afar depression lies at the triple junction between the African, Arabian, and Somalian plates (in the Horn of Africa), where the unique combination of observational data from structural mapping, seismicity, and Global Navigation Satellite System (GNSS) allows us to understand the link between fault kinematics and plate motions. We complement these observations with an analog model to gain insights into how the patterns and directions of faults relate to overall plate motions. A key finding in both the model and nature is that some adjacent normal faults form at high angles and generate T-shaped structures. These purely normal faults are synchronously active, which means that the extension direction varies ∼90° locally. These kinematic contrasts in our model and in nature occur despite the relatively smooth pattern of overall surface motions. The results indicate that normal faults interacting at high angles to form the T-shaped structures can evolve synchronously within a stress field that varies gently in magnitude but dramatically in orientation over a few kilometers.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140435571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Plate reconstructions reveal that two secular centers of convergence formed beneath eastern Eurasia and North America no later than 200 Ma. The cause of these convergence centers, which featured flat subduction, slab stagnation, and/or continental margin subduction, remains uncertain. Here, we propose that upper-mantle thermal inhomogeneity, particularly an anomalously cool Northern Hemispheric upper mantle, was a fundamental driver of this long-lived convergence. By considering the pattern of observed thermal inhomogeneity, our numerical models show that flow-induced asymmetrical subduction will tend to develop toward cold mantle domains, even when the subducting plate is buoyant. The models can reproduce the diverse subduction styles observed in the Northern Hemisphere by including proposed pre-subduction plate distributions and/or properties.
{"title":"Long-lived Northern Hemisphere convergence systems driven by upper-mantle thermal inhomogeneity","authors":"Liang Liu, Zebin Cao, J.P. Morgan, Hongyan Li, Fan Yang, Yi-Gang Xu","doi":"10.1130/g51948.1","DOIUrl":"https://doi.org/10.1130/g51948.1","url":null,"abstract":"Plate reconstructions reveal that two secular centers of convergence formed beneath eastern Eurasia and North America no later than 200 Ma. The cause of these convergence centers, which featured flat subduction, slab stagnation, and/or continental margin subduction, remains uncertain. Here, we propose that upper-mantle thermal inhomogeneity, particularly an anomalously cool Northern Hemispheric upper mantle, was a fundamental driver of this long-lived convergence. By considering the pattern of observed thermal inhomogeneity, our numerical models show that flow-induced asymmetrical subduction will tend to develop toward cold mantle domains, even when the subducting plate is buoyant. The models can reproduce the diverse subduction styles observed in the Northern Hemisphere by including proposed pre-subduction plate distributions and/or properties.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140442922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Odlum, T. Capaldi, Kelly D. Thomson, D. Stockli
Sedimentary basins provide a deep time archive of tectonic and Earth-surface processes that can be leveraged by detrital mineral U-Pb dating and geochemistry to track paleogeography, magmatism, and crustal evolution. Zircon preserves the long-term (billions of years) record of supercontinent cycles; however, it is biased toward preserving felsic crustal records. Detrital rutile complements the detrital zircon record by providing constraints on the time and temperature of rifting and mafic magmatism, metamorphism, exhumation of the middle and lower crust, subduction, and amagmatic orogenesis. We use detrital zircon U-Pb and detrital rutile U-Pb geochronology and trace element analysis of Permian to Eocene siliciclastic rocks in the southern Pyrenees to capture supercontinent cycles of ocean basins opening and closing. Detrital rutile age spectra show peaks at ca. 100 Ma associated with rifting and hyperextension in the Pyrenean realm, 200 Ma associated with the Central Atlantic Magmatic Province, and 330 Ma, 375 Ma, and 400 Ma associated with subduction and Rheic Ocean crust formation. Zr-in-rutile thermometry and rutile Cr-Nb systematics provide further insight into metamorphic facies (peak metamorphic temperatures) and source rock lithology (mafic versus felsic affinity). Detrital zircon age spectra have peaks at ca. 300 Ma, 450 Ma, and 600 Ma associated with major orogenic events and felsic magmatism, and Th/U ratios provide information on relative zircon formation temperatures. Comparison of these independent records shows that detrital rutile reflects rifting, magma-poor orogenesis, and oceanic lithospheric processes, while detrital zircon detects continental lithospheric processes. Integrated detrital zircon and rutile data sets archive past geological events across multiple Wilson cycles.
沉积盆地提供了构造和地球表面过程的深层时间档案，可通过碎屑矿物 U-Pb 测定和地球化学来追踪古地理、岩浆活动和地壳演化。锆石保存了超大陆周期的长期（数十亿年）记录；但是，它偏向于保存长岩地壳记录。碎屑金红石补充了碎屑锆石的记录，为断裂和镁质岩浆作用、变质作用、中下部地壳掘出、俯冲和岩浆造山运动的时间和温度提供了约束条件。我们利用对比利牛斯山脉南部二叠纪至始新世硅质碎屑岩进行的锆英石U-Pb和金红石U-Pb地质年代和痕量元素分析，来捕捉大洋盆地开启和关闭的超大陆周期。碎屑金红石年龄谱显示，在约 100 Ma 时出现峰值，与断裂和超断裂有关。100 Ma与比利牛斯地区的断裂和过度延伸有关，200 Ma与中大西洋岩浆省有关，330 Ma、375 Ma和400 Ma与俯冲和莱茵洋地壳形成有关。金红石中的锆石温度测定法和金红石中的铬-铌系统学进一步揭示了变质面（变质峰值温度）和源岩岩性（岩浆岩与长岩的亲和性）。碎屑锆石年龄谱在大约 300 Ma、450 Ma 和 600 Ma 处出现峰值。Th/U比值提供了锆石相对形成温度的信息。对这些独立记录的比较表明，金红石碎屑反映了断裂、贫岩浆造山运动和大洋岩石圈过程，而锆英石碎屑则探测了大陆岩石圈过程。综合的碎屑锆石和金红石数据集记录了多个威尔逊周期中过去的地质事件。
{"title":"Tracking cycles of Phanerozoic opening and closing of ocean basins using detrital rutile and zircon geochronology and geochemistry","authors":"M. Odlum, T. Capaldi, Kelly D. Thomson, D. Stockli","doi":"10.1130/g51826.1","DOIUrl":"https://doi.org/10.1130/g51826.1","url":null,"abstract":"Sedimentary basins provide a deep time archive of tectonic and Earth-surface processes that can be leveraged by detrital mineral U-Pb dating and geochemistry to track paleogeography, magmatism, and crustal evolution. Zircon preserves the long-term (billions of years) record of supercontinent cycles; however, it is biased toward preserving felsic crustal records. Detrital rutile complements the detrital zircon record by providing constraints on the time and temperature of rifting and mafic magmatism, metamorphism, exhumation of the middle and lower crust, subduction, and amagmatic orogenesis. We use detrital zircon U-Pb and detrital rutile U-Pb geochronology and trace element analysis of Permian to Eocene siliciclastic rocks in the southern Pyrenees to capture supercontinent cycles of ocean basins opening and closing. Detrital rutile age spectra show peaks at ca. 100 Ma associated with rifting and hyperextension in the Pyrenean realm, 200 Ma associated with the Central Atlantic Magmatic Province, and 330 Ma, 375 Ma, and 400 Ma associated with subduction and Rheic Ocean crust formation. Zr-in-rutile thermometry and rutile Cr-Nb systematics provide further insight into metamorphic facies (peak metamorphic temperatures) and source rock lithology (mafic versus felsic affinity). Detrital zircon age spectra have peaks at ca. 300 Ma, 450 Ma, and 600 Ma associated with major orogenic events and felsic magmatism, and Th/U ratios provide information on relative zircon formation temperatures. Comparison of these independent records shows that detrital rutile reflects rifting, magma-poor orogenesis, and oceanic lithospheric processes, while detrital zircon detects continental lithospheric processes. Integrated detrital zircon and rutile data sets archive past geological events across multiple Wilson cycles.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140443146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Volker Vahrenkamp, V. Chandra, E. Garuglieri, R. Marasco, Kai Hachmann, Pankaj Khanna, Daniele Daffonchio, Alexander Petrovic
Microbial carbonates, and stromatolites in particular, represent the earliest geological record of life on Earth, which dominated the planet as the sole biotic carbonate factory for almost 3 b.y., from the Archean to the late Proterozoic. Rare and sparsely scattered across the globe in the present day, modern “living” stromatolites are typically relegated to extreme environmental niches, remaining as vestiges of a prodigious microbial past. Here, we report the first discovery of living shallow-marine stromatolites in the Middle East, on Sheybarah Island, Al Wajh carbonate platform, on the NE Red Sea shelf (Saudi Arabia). We detail their regional distribution and describe their environmental conditions, internal structures, and microbial diversity. We also report the first discovery of reticulated filaments in a photic setting, associated with these stromatolites. The Sheybarah stromatolites occur in the intertidal to shallow subtidal zones along the seaward-facing beach in three depth-dependent growth forms. Their inner layers were formed by microbially mediated accretion and differential lithification of sediment grains. Compositional microbial analysis revealed the presence of a wide range of microbial life forms.
微生物碳酸盐，尤其是叠层石，代表了地球上生命最早的地质记录，作为唯一的生物碳酸盐工厂，它们在地球上占据了将近 3 亿年的时间，从早生代到晚新生代。现代的 "活 "叠层石非常罕见，稀少地分布在全球各地，通常被置于极端的环境壁龛中，成为过去大量微生物的遗迹。在这里，我们报告了在中东地区首次发现的活体浅海叠层石，位于红海大陆架东北部（沙特阿拉伯）的 Al Wajh 碳酸盐平台 Sheybarah 岛上。我们详细介绍了它们的区域分布情况，并描述了它们的环境条件、内部结构和微生物多样性。我们还报告了在光环境中首次发现的与这些叠层石有关的网状细丝。Sheybarah叠层石出现在向海海滩的潮间带到浅亚潮带，有三种深度生长形式。它们的内层是由微生物介导的沉积物颗粒增生和差异岩化形成的。微生物成分分析表明存在多种微生物生命形式。
{"title":"Discovery of modern living intertidal stromatolites on Sheybarah Island, Red Sea, Saudi Arabia","authors":"Volker Vahrenkamp, V. Chandra, E. Garuglieri, R. Marasco, Kai Hachmann, Pankaj Khanna, Daniele Daffonchio, Alexander Petrovic","doi":"10.1130/g51793.1","DOIUrl":"https://doi.org/10.1130/g51793.1","url":null,"abstract":"Microbial carbonates, and stromatolites in particular, represent the earliest geological record of life on Earth, which dominated the planet as the sole biotic carbonate factory for almost 3 b.y., from the Archean to the late Proterozoic. Rare and sparsely scattered across the globe in the present day, modern “living” stromatolites are typically relegated to extreme environmental niches, remaining as vestiges of a prodigious microbial past. Here, we report the first discovery of living shallow-marine stromatolites in the Middle East, on Sheybarah Island, Al Wajh carbonate platform, on the NE Red Sea shelf (Saudi Arabia). We detail their regional distribution and describe their environmental conditions, internal structures, and microbial diversity. We also report the first discovery of reticulated filaments in a photic setting, associated with these stromatolites. The Sheybarah stromatolites occur in the intertidal to shallow subtidal zones along the seaward-facing beach in three depth-dependent growth forms. Their inner layers were formed by microbially mediated accretion and differential lithification of sediment grains. Compositional microbial analysis revealed the presence of a wide range of microbial life forms.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139774633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Volker Vahrenkamp, V. Chandra, E. Garuglieri, R. Marasco, Kai Hachmann, Pankaj Khanna, Daniele Daffonchio, Alexander Petrovic
Microbial carbonates, and stromatolites in particular, represent the earliest geological record of life on Earth, which dominated the planet as the sole biotic carbonate factory for almost 3 b.y., from the Archean to the late Proterozoic. Rare and sparsely scattered across the globe in the present day, modern “living” stromatolites are typically relegated to extreme environmental niches, remaining as vestiges of a prodigious microbial past. Here, we report the first discovery of living shallow-marine stromatolites in the Middle East, on Sheybarah Island, Al Wajh carbonate platform, on the NE Red Sea shelf (Saudi Arabia). We detail their regional distribution and describe their environmental conditions, internal structures, and microbial diversity. We also report the first discovery of reticulated filaments in a photic setting, associated with these stromatolites. The Sheybarah stromatolites occur in the intertidal to shallow subtidal zones along the seaward-facing beach in three depth-dependent growth forms. Their inner layers were formed by microbially mediated accretion and differential lithification of sediment grains. Compositional microbial analysis revealed the presence of a wide range of microbial life forms.
微生物碳酸盐，尤其是叠层石，代表了地球上生命最早的地质记录，作为唯一的生物碳酸盐工厂，它们在地球上占据了将近 3 亿年的时间，从早生代到晚新生代。现代的 "活 "叠层石非常罕见，稀少地分布在全球各地，通常被置于极端的环境壁龛中，成为过去大量微生物的遗迹。在这里，我们报告了在中东地区首次发现的活体浅海叠层石，位于红海大陆架东北部（沙特阿拉伯）的 Al Wajh 碳酸盐平台 Sheybarah 岛上。我们详细介绍了它们的区域分布情况，并描述了它们的环境条件、内部结构和微生物多样性。我们还报告了在光环境中首次发现的与这些叠层石有关的网状细丝。Sheybarah叠层石出现在向海海滩的潮间带到浅亚潮带，有三种深度生长形式。它们的内层是由微生物介导的沉积物颗粒增生和差异岩化形成的。微生物成分分析表明存在多种微生物生命形式。
{"title":"Discovery of modern living intertidal stromatolites on Sheybarah Island, Red Sea, Saudi Arabia","authors":"Volker Vahrenkamp, V. Chandra, E. Garuglieri, R. Marasco, Kai Hachmann, Pankaj Khanna, Daniele Daffonchio, Alexander Petrovic","doi":"10.1130/g51793.1","DOIUrl":"https://doi.org/10.1130/g51793.1","url":null,"abstract":"Microbial carbonates, and stromatolites in particular, represent the earliest geological record of life on Earth, which dominated the planet as the sole biotic carbonate factory for almost 3 b.y., from the Archean to the late Proterozoic. Rare and sparsely scattered across the globe in the present day, modern “living” stromatolites are typically relegated to extreme environmental niches, remaining as vestiges of a prodigious microbial past. Here, we report the first discovery of living shallow-marine stromatolites in the Middle East, on Sheybarah Island, Al Wajh carbonate platform, on the NE Red Sea shelf (Saudi Arabia). We detail their regional distribution and describe their environmental conditions, internal structures, and microbial diversity. We also report the first discovery of reticulated filaments in a photic setting, associated with these stromatolites. The Sheybarah stromatolites occur in the intertidal to shallow subtidal zones along the seaward-facing beach in three depth-dependent growth forms. Their inner layers were formed by microbially mediated accretion and differential lithification of sediment grains. Compositional microbial analysis revealed the presence of a wide range of microbial life forms.","PeriodicalId":503125,"journal":{"name":"Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139834394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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