1区地球科学

Geology Pub Date : 2023-10-12 DOI: 10.1130/g51730.1

Po Wan Wong, Ivar Midtkandal, Jan Inge Faleide

{"title":"Origin of paired extension-compression during rotational rifting: An early Paleogene example from the northeast Atlantic region and its implications","authors":"Po Wan Wong, Ivar Midtkandal, Jan Inge Faleide","doi":"10.1130/g51730.1","DOIUrl":"https://doi.org/10.1130/g51730.1","url":null,"abstract":"The formation of paired extension-compression (PEC) postulated by rotational kinematics of rift propagation is demonstrated by analogue models but rarely observed in nature. In our study of the early Paleogene continental rift in the northeast Atlantic, a PEC is proposed based on the northeastward propagation and the coeval compression at the rift tip. The propagation is deduced from tectono-magmatic trends, including along-axis development of magmatism, and migration of tectonic faulting inward and toward the rift tip. Where this propagation terminated, we documented coeval extension and compression in the form of a horst-and-graben system (H&G) and V-shaped anticline (VA), respectively. Given their structural characteristics and spatiotemporal relationships with the rift, their origin is best illustrated by a three-stage model: (1) Rifting initiated at the site of mantle upwelling and propagated northeastward in the Paleocene. (2) The rift tip was stalled by an elevated mafic-ultramafic body at the Barents Shelf, which led to forward projection of the rift’s driving force to create the H&G and the VA (PEC), dissipating the along-axis force component. (3) Domination of axis-perpendicular components then promoted orthogonal extension and sheared margin development. Our study suggests that PEC has a crucial role in both termination of propagation and rift-mode conversion.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"248 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135967921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A long-lived mafic magma reservoir: Zircon evidence from a hornblende peridotite in the Hida Belt, Japan 一个长寿的基性岩浆储层:来自日本飞驒带角闪橄榄岩的锆石证据

1区地球科学

Geology Pub Date : 2023-10-11 DOI: 10.1130/g51560.1

Keita Itano, Mami Takehara, Kenji Horie, Tsuyoshi Iizuka, Ikuya Nishio, Tomoaki Morishita

{"title":"A long-lived mafic magma reservoir: Zircon evidence from a hornblende peridotite in the Hida Belt, Japan","authors":"Keita Itano, Mami Takehara, Kenji Horie, Tsuyoshi Iizuka, Ikuya Nishio, Tomoaki Morishita","doi":"10.1130/g51560.1","DOIUrl":"https://doi.org/10.1130/g51560.1","url":null,"abstract":"Zircon geochronology has contributed to our understanding of the longevity of transcrustal magmatic systems; however, most studies focus on zircon records from felsic rocks due to the restricted occurrence of zircon in mafic-ultramafic rocks. We present U−Pb age, geochemical, and Hf−O isotope data for zircons from a hornblendite peridotite in the Hida Belt, Japan, that offers a unique opportunity to investigate the lifetime of a long-lived mafic plumbing system in an arc setting. We found two zircon U−Pb age clusters: an incompatible element-rich cluster at 196 Ma and an incompatible element-poor cluster at 186 Ma. Their homogeneous isotopic signatures (δ18O = 7.7‰ ± 0.8‰, εHf = 10.3‰ ± 1.7‰) indicate the same magma source despite the 10 m.y. age gap. These two clusters are explained by different zircon formation mechanisms that differ depending on whether or not zircon saturation requires differentiated melt with high SiO2. The enriched older zircons formed by local zircon saturation at the mafic melt-olivine interface, whereas the younger depleted zircons precipitated from the last drop of interstitial felsic melt co-existing with hornblendes. Our finding substantiates the longevity of mafic systems at lower crusts, which sustain transcrustal magma systems and crustal evolution.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136211434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Ice-rafted dropstones at midlatitudes in the Cretaceous of continental Iberia 伊比利亚大陆白垩纪中纬度地区的浮冰坠石

1区地球科学

Geology Pub Date : 2023-10-10 DOI: 10.1130/g51725.1

Juan Pedro Rodríguez-López, Carlos L. Liesa, Aránzazu Luzón, Arsenio Muñoz, María J. Mayayo, Julian B. Murton, Ana R. Soria

引用次数: 0

Seafloor spreading and the delivery of sulfur and metals to Earth’s oceans 海底扩张以及硫和金属向地球海洋的输送

1区地球科学

Geology Pub Date : 2023-10-05 DOI: 10.1130/g51311.1

Drew D. Syverson, Adedapo N. Awolayo, Benjamin M. Tutolo

{"title":"Seafloor spreading and the delivery of sulfur and metals to Earth’s oceans","authors":"Drew D. Syverson, Adedapo N. Awolayo, Benjamin M. Tutolo","doi":"10.1130/g51311.1","DOIUrl":"https://doi.org/10.1130/g51311.1","url":null,"abstract":"Circulating fluids within Earth’s mid-ocean ridge system cool and alter the oceanic crust, contribute distinct chemistry to the ocean, and generate economically and geologically important metal-sulfide deposits at the seafloor. Yet, we have few constraints on the characteristics of these fluids at peak subseafloor pressure and temperature conditions or how the primary variable, seafloor spreading, affects these fluids’ delivery of metals and sulfur to seawater. Here, we develop a new, robust technique for estimating the peak endowment of heat and dissolved sulfur, iron, and copper in subseafloor hydrothermal fluids and determining their fate as these superheated fluids rise to the seafloor. Calculations using this technique indicate that &gt;20%−70% of sulfur, iron, and copper dissolved at peak subseafloor conditions are lost during upflow due to cooling and concomitant decreases in sulfide mineral solubility. The interpretation of these estimates within the geologic context of vent fields allows us to demonstrate a strong inverse relationship between seafloor spreading rate and peak pressure-temperature conditions, subseafloor heat loss, and the magnitude of subseafloor sulfide mineralization. Our results demonstrate the extent to which the secular variation of Earth’s mid-ocean ridge system over geologic time has impacted sulfide deposition rates and hydrothermal fluxes of sulfur and metals to the ocean.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134975639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Relationships between fluvial dune cross-set thickness, planview width, and trough geometry 河流沙丘交叉集厚度、平面宽度和槽几何之间的关系

1区地球科学

Geology Pub Date : 2023-10-05 DOI: 10.1130/g51540.1

Benjamin T. Cardenas, Kaitlyn Stacey, Zachary J. Baran

{"title":"Relationships between fluvial dune cross-set thickness, planview width, and trough geometry","authors":"Benjamin T. Cardenas, Kaitlyn Stacey, Zachary J. Baran","doi":"10.1130/g51540.1","DOIUrl":"https://doi.org/10.1130/g51540.1","url":null,"abstract":"Sedimentary structures provide critical information for the reconstruction of ancient environments of Earth and other planets. Fluvial dune cross sets, structures that record dune migration via the filling of leading troughs along ancient riverbeds, are particularly useful. Most quantitative methods for interpreting cross sets require thickness measurements, but the growth of planview imaging of sedimentary rocks on Earth and Mars has introduced a need for methods to interpret planview exposures of cross sets. Here, we measured 359 cross-set widths exposed along ancient channel belts of the Cretaceous Cedar Mountain Formation exposed in Utah, USA, and compared these widths to published thicknesses (n = 350). We found that the mean cross-set width was 1.29 m, 9.3 times the mean thickness. The normalized distributions of widths and thicknesses were statistically similar and thus contained similar paleoenvironmental information. Numerical experiments representing a series of trough cut-and-fill structures show that cross-set reworking is equally important in setting width as thickness and that the observed cross-set widths could be explained by a gamma-distributed range of trough widths with a mean of 2.96 ± 0.25 m, ∼2.3 times cross-set width. Given the similarity of dune-field geometries across depositional settings and planetary boundary conditions, we suggest this cross-set width-to-thickness relationship could be useful for interpreting other cross sets exposed in planview.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135482784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The volatile record of volcanic apatite and its implications for the formation of porphyry copper deposits 火山磷灰石的挥发性记录及其对斑岩铜矿床形成的启示

1区地球科学

Geology Pub Date : 2023-10-05 DOI: 10.1130/g51461.1

George Stonadge, Andrew Miles, Daniel Smith, Simon Large, Thomas Knott

{"title":"The volatile record of volcanic apatite and its implications for the formation of porphyry copper deposits","authors":"George Stonadge, Andrew Miles, Daniel Smith, Simon Large, Thomas Knott","doi":"10.1130/g51461.1","DOIUrl":"https://doi.org/10.1130/g51461.1","url":null,"abstract":"Volatile saturation influences the physicochemical behavior of magmas and is essential for the sequestration of metals in porphyry copper deposits. Tracking the evolution of volatile components (F, Cl, H2O, S) in arc systems is complicated by their mobility and tendency to rapidly re-equilibrate with late-stage melts. We demonstrate that accurate measurements of volatile concentrations in apatite offer a reliable method for identifying the occurrence of volatile saturation. Fluorine, Cl, S, and calculated OH concentrations in apatite obtained by scanning electron microscope−energy-dispersive X-ray spectroscopy and electron microprobe analysis were used to compare two end-member volcanic systems in the West Luzon Arc (Philippines): Pinatubo (a fluid-saturated analogue for porphyry copper deposits) and Taal (a barren and fluid-undersaturated comparator). Apatites from Pinatubo are S-rich (0.04−0.64 wt%) and show a progressive decrease in XCl/XOH (0.6−0.25) and an increase in XF/XCl (1.5−8) and XF/XOH (0.75−1.2) during crystallization. Modeling indicates that these changes result from efficient partitioning of Cl into a continuously saturated H2O-rich fluid, while high regions of S in apatite reflect episodic flushing by a separate S-rich flux. Little S is evident in apatites from Taal (&lt;300 ppm), which show increasing XCl/XOH and XF/XOH together with constant XF/XCl during crystallization. This cannot be explained using an H2O-saturated model, and instead reflects fluid-undersaturated crystallization and cooling in a reduced and/or S-depleted system. Measured volatiles in apatite therefore effectively discriminate volatile-saturated and undersaturated magmatic systems, providing an important ‘fertility’ filter for porphyry exploration.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135481260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Lithospheric-scale dynamics during continental subduction: Evidence from a frozen-in plate interface 大陆俯冲过程中的岩石圈尺度动力学:来自冻结板块界面的证据

1区地球科学

Geology Pub Date : 2023-10-04 DOI: 10.1130/g51480.1

Kevin Mendes, Philippe Agard, Alexis Plunder, Clément Herviou

{"title":"Lithospheric-scale dynamics during continental subduction: Evidence from a frozen-in plate interface","authors":"Kevin Mendes, Philippe Agard, Alexis Plunder, Clément Herviou","doi":"10.1130/g51480.1","DOIUrl":"https://doi.org/10.1130/g51480.1","url":null,"abstract":"Continental subduction and collision are not merely follow-ups of oceanic subduction but mark the transition from lithospheric-scale deformation localized along the subduction interface to crustal-scale deformation distributed across the orogen. In order to unravel the processes typifying the dynamic changes from oceanic subduction to collision, we have characterized the pressure-temperature (P-T) and spatio-temporal evolution of rocks on each side of the tectonic contact (Briançonnais−Liguro-Piemont [Br-LP] contact) separating the subducted oceanic remnants from the subducted continental fragments along the Western Alps. Results indicate that the maximum temperature and pressure difference on each side of the contact is generally &lt;30 °C and &lt;0.3 GPa, evidencing that no significant metamorphic gap exists. The preservation of similar P-T conditions on both sides of the Br-LP contact is interpreted as resulting from offscraping of the Liguro-Piemont and later Briançonnais units at similar depths, as supported by the ∼10 m.y. gap between peak burial ages of both zones. The similar depth range reached by the various units reflects systematic variations of slicing and mechanical coupling along the plate interface suggesting that (1) similar slicing mechanisms and strain localization prevailed during both oceanic and continental subduction, and (2) the Br-LP contact represents a frozen-in subduction interface. The end of high-pressure and low-temperature metamorphism and continental subduction at ca. 33 Ma would mark the stalling of subduction interface dynamics and the onset of strain distribution across the plate interface and into the lower plate.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135644089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Identifying plutons associated with long-lived volcanism by thermal modeling of contact metamorphic aureoles 通过接触变质环的热模拟识别与长寿命火山作用有关的岩体

1区地球科学

Geology Pub Date : 2023-10-04 DOI: 10.1130/g51563.1

Ken Yamaoka, Simon R. Wallis, Akira Miyake, Catherine Annen

引用次数: 0

Strength of the winter North Atlantic jet stream has deviated from its natural trend under anthropogenic warming 在人为变暖的影响下，北大西洋冬季急流的强度偏离了其自然趋势

1区地球科学

Geology Pub Date : 2023-10-03 DOI: 10.1130/g51329.1

Miaofa Li, Binggui Cai, Slobodan B. Marković, Luo Wang, Qingzhen Hao, Andy Baker, Milivoj B. Gavrilov, Liyuan Jiang, Fang Wang, Xuefeng Wang, Lisheng Wang, Zhibang Ma, Jule Xiao, Zhengtang Guo

{"title":"Strength of the winter North Atlantic jet stream has deviated from its natural trend under anthropogenic warming","authors":"Miaofa Li, Binggui Cai, Slobodan B. Marković, Luo Wang, Qingzhen Hao, Andy Baker, Milivoj B. Gavrilov, Liyuan Jiang, Fang Wang, Xuefeng Wang, Lisheng Wang, Zhibang Ma, Jule Xiao, Zhengtang Guo","doi":"10.1130/g51329.1","DOIUrl":"https://doi.org/10.1130/g51329.1","url":null,"abstract":"The North Atlantic jet stream (NAJ) has a profound impact on the climate of the North Atlantic−European sector, especially in winter. Observations show that the winter NAJ (NAJw) has strengthened over the past ∼140 yr. However, it remains unclear whether this long-term trend has deviated from the natural variability. Here, we present a 2500-yr-long reconstruction of NAJw strength using high-quality stalagmite δ18O records from southeastern Europe. Our results show that the NAJw weakened during both the Roman Warm Period (B.C. 300−A.D. 200) and the Medieval Warm Period (A.D. 900−1250) but that it has strengthened under anthropogenic warming (since A.D. 1850). This indicates that its current trend has already deviated from the natural variability. The best explanation for this present anomalous trend of NAJw strength is that it was triggered by the appearance of the North Atlantic warming hole under anthropogenic forcing. This anomalous trend suggests that continued global warming may further strengthen the NAJw in the future.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135689533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Understanding the Ries impact structure subsurface from high-resolution seismic data 从高分辨率地震数据了解里斯撞击构造

1区地球科学

Geology Pub Date : 2023-09-28 DOI: 10.1130/g51503.1

Naoma McCall, Sean P.S. Gulick, Kaidi Karro, Argo Jõeleht, Jakob Wilk, Gisela Pösges

{"title":"Understanding the Ries impact structure subsurface from high-resolution seismic data","authors":"Naoma McCall, Sean P.S. Gulick, Kaidi Karro, Argo Jõeleht, Jakob Wilk, Gisela Pösges","doi":"10.1130/g51503.1","DOIUrl":"https://doi.org/10.1130/g51503.1","url":null,"abstract":"The Ries impact structure (southern Germany) formed ca. 15 Ma and is 22−26 km in diameter, making it one of the youngest and best-preserved mid-size terrestrial impact craters, yet the subsurface has not been studied with modern geophysics. We present the first high-resolution seismic profiles of the Ries impact structure; the profiles show discontinuous intra-basement reflectors and a central crater floor without a significant central topographic high. The inner crystalline ring sits adjacent to, not on top of, the crater terrace zone. These morphologies indicate that during the crater modification stage, the rebounding central uplift at Ries rose and then collapsed without the continued outward motion required to form a fully developed peak ring. The Ries impact structure may be best considered a transitional complex crater form between a central-peak crater and a peak-ring crater as documented on the Moon and other rocky planets. A series of high-amplitude, discontinuous, topographically influenced reflectors overlying the basement implies that the suevite within the crater basin was emplaced via lateral transport.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135385146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

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