Geology最新文献_第10页

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

Ammonium “nutrient capacitor” model for δ15N signatures associated with marine anoxic events 海洋缺氧事件δ15N特征的铵态“营养电容”模型

1区地球科学

Geology Pub Date : 2023-09-28 DOI: 10.1130/g51527.1

Benjamin T. Uveges, Ann Pearson

引用次数: 0

Mantle metasomatism induced by water-fluxed melting of subducted continental crust at ultrahigh pressures 由俯冲大陆地壳在超高压下的水溶熔融引起的地幔交代作用

1区地球科学

Geology Pub Date : 2023-09-27 DOI: 10.1130/g51547.1

Mingdi Gao, Stephen F. Foley, Haijin Xu, Yu Wang

{"title":"Mantle metasomatism induced by water-fluxed melting of subducted continental crust at ultrahigh pressures","authors":"Mingdi Gao, Stephen F. Foley, Haijin Xu, Yu Wang","doi":"10.1130/g51547.1","DOIUrl":"https://doi.org/10.1130/g51547.1","url":null,"abstract":"Mantle metasomatism under ultrahigh-pressure (UHP) conditions is widely recognized in orogenic peridotites and pyroxenites from UHP terranes. However, the processes by which the deeply subducted continental crust reacts with the mantle remain obscure. To investigate the metasomatic regime under UHP conditions, we conducted layered reaction experiments between gneiss and peridotite at 5 GPa and 800−1100 °C, with free water added in some of the experiments. At temperatures below the gneiss solidus, the major metasomatic agent is aqueous fluid, with the main reaction products being orthopyroxene + phlogopite + K-richterite. At temperatures above the gneiss solidus, hydrous melt becomes the major metasomatic agent, and the major reaction products vary from orthopyroxene + phlogopite to orthopyroxene + garnet with increasing degree of melting. The transformation from phlogopite to garnet occurred between 1000 °C and 1100 °C for runs without water added and between 800 °C and 900 °C for runs with water added. Pyroxenites in UHP terranes are mainly characterized by the metasomatic growth of orthopyroxene and garnet at 4−6 GPa and 750−1000 °C. Only experiments with water added reproduced the metasomatic assemblage at similar pressure-temperature conditions, indicating that mantle metasomatism in UHP terranes is probably mainly induced by water-fluxed melting of the continental crust under UHP conditions.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135535230","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

Controls on upstream-migrating bed forms in sandy submarine channels 沙质海底河道上游迁移河床形态的控制

1区地球科学

Geology Pub Date : 2023-09-27 DOI: 10.1130/g51385.1

Rebecca G. Englert, Age J. Vellinga, Matthieu J.B. Cartigny, Michael A. Clare, Joris T. Eggenhuisen, Stephen M. Hubbard

{"title":"Controls on upstream-migrating bed forms in sandy submarine channels","authors":"Rebecca G. Englert, Age J. Vellinga, Matthieu J.B. Cartigny, Michael A. Clare, Joris T. Eggenhuisen, Stephen M. Hubbard","doi":"10.1130/g51385.1","DOIUrl":"https://doi.org/10.1130/g51385.1","url":null,"abstract":"Submarine channels parallel river channels in their ability to transport sediment. However in contrast to rivers, sediment transport and bed-form development in submarine channels are less well understood. Many steep (&gt;1°), sandy submarine channels are dominated by upstream-migrating bed forms. The flow conditions required to form these upstream-migrating bed forms remain debated because the interactions between turbidity currents and active bed forms are difficult to measure directly. Consequently, we used a depth-resolved numerical model to test the role of flow parameters that are hypothesized to control the formation of upstream-migrating bed forms in submarine channels. While our modeling results confirmed the importance of previously identified flow parameters (e.g., densiometric Froude number), we found that basal sediment concentration in turbidity currents is the strongest predictor of upstream-migrating bed-form formation. Our model shows how locally steep gradients enable high sediment concentrations (average &gt;5 vol%) in the basal parts of flows, which allow the development of cyclic step instabilities and their associated bed forms. This new insight explains the previously puzzling observation that upstream-migrating bed forms are abundant in proximal, steep, sandy reaches of submarine channels, while their occurrence becomes more intermittent downslope.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135535536","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

"Wrecking the rocks": Continental weathering by groundwater “破坏岩石”:地下水对大陆的风化作用

1区地球科学

Geology Pub Date : 2023-09-27 DOI: 10.1130/g51571.1

Warren W. Wood, Ward E. Sanford, John A. Cherry, Warren T. Wood

{"title":"\"Wrecking the rocks\": Continental weathering by groundwater","authors":"Warren W. Wood, Ward E. Sanford, John A. Cherry, Warren T. Wood","doi":"10.1130/g51571.1","DOIUrl":"https://doi.org/10.1130/g51571.1","url":null,"abstract":"Groundwater solute mass flux discharged from the continents to the oceans is between 56% and 63% of particulate sediment transport mass flux. Herein we utilized newly developed continental geospatial groundwater concentration estimates that were multiplied by groundwater volumetric recharge flux to provide a continental-scale discharge mass flux to the oceans of 7.3 Pg DS/yr (petagrams dissolved solutes per year). This mass flux was evaluated from six continental ecosystems: direct ocean discharge (0.28 Pg DS/yr), endorheic basins (0.59 Pg DS/yr), cold-wet exorheic basins (0.55 Pg DS/yr), cold-dry exorheic basins (1.1 Pg DS/yr), warm-dry exorheic basins (0.82 Pg DS/yr), and warm-wet exorheic basins (4.0 Pg DS/yr), thus providing insight into the role of rainfall and temperature on continental weathering and denudation. A new, robust molar silicate/carbonate ratio of 0.42 was calculated for weathering of continental rocks, which is important in the Urey model of climate change. We estimate that rock weathering accounts for ∼50% of the total solute mass flux discharged from the continents, the remainder being from externally derived marine aerosols and organic-derived bicarbonate.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135536463","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

Insights into initial continental rifting of marginal seas from seismic evidence for slab relics in the mid-mantle of the Woodlark rift, southwestern Pacific 从西南太平洋伍德拉克裂谷中地幔板块遗迹的地震证据看边缘海的初始大陆裂谷

1区地球科学

Geology Pub Date : 2023-09-26 DOI: 10.1130/g51528.1

Youqiang Yu, Frederik Tilmann, Stephen S. Gao, Kelly H. Liu, Jiaji Xi

引用次数: 0

Oceanic serpentinites: A potentially critical reservoir for deep nitrogen recycling 海洋蛇纹岩:深层氮循环的潜在关键储层

1区地球科学

Geology Pub Date : 2023-09-21 DOI: 10.1130/g51464.1

Kan Li, Amber Jie Yu, Peter H. Barry, Long Li

{"title":"Oceanic serpentinites: A potentially critical reservoir for deep nitrogen recycling","authors":"Kan Li, Amber Jie Yu, Peter H. Barry, Long Li","doi":"10.1130/g51464.1","DOIUrl":"https://doi.org/10.1130/g51464.1","url":null,"abstract":"Serpentinized oceanic peridotites might be an important reservoir delivering volatile elements including nitrogen (N) into the mantle via subduction. To determine N sources and estimate the budget of alteration-added secondary N in the oceanic mantle peridotite reservoir, we examined oceanic serpentinites from four Ocean Drilling Program (ODP) sites in the Pacific and Atlantic Oceans. Our results showed that, despite large variation in serpentinization condition (high temperatures up to &gt;350 °C at Holes 895D, 1271B, and 920D; low temperatures &lt;150 °C at Hole 1274A), serpentinites from all sites displayed ubiquitous and similar magnitude of N enrichment (3.2−18.6 ppm) from sediments/seawater sources (δ15N = −3.3‰ to +4.4‰), and these values were significantly elevated relative to the low N concentration (0.04−2.0 ppm) and δ15N value (−5‰ ± 2‰) of the depleted mantle. Based on these data, the serpentinized oceanic mantle is estimated to contribute 0.4 ± 0.2−14.7 ± 6.9 × 109 mol N annually to global subduction zones. Although this flux is smaller than that of subducting sediments (57 × 109 mol·yr−1), comparison between oceanic serpentinites and meta-serpentinites from subduction zones suggests that N can be effectively retained in serpentinites during prograde metamorphism. This implies that the serpentinized slab mantle could be a critical reservoir to deliver N enriched in 15N to the mantle (at least 70 km depth) and potentially to the deepest portions of the mantle sampled by deep-rooted mantle plumes.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136130971","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