K. Fauquembergue, T. Mulder, J. Reijmer, V. Hanquiez, C. Betzler, E. Ducassou, A. Recouvreur, M. Principaud, J. Borgomano, S. Wilk, E. Poli
Slopes adjacent to the Bahamian carbonate platform revealed a large variety of depositional processes. In this study, we present a synthesis summarizing 109,000 km2 of bathymetric and reflectivity data with ∼7,900 km of seismic lines and 311 m of sediment cores that were obtained over the last 50 years. These data are used to develop a conceptual model of sedimentation patterns on Quaternary carbonate slope systems and their interaction with the adjacent shallow-water carbonate platforms. Our data highlight that during the Quaternary, factors controlling large-scale sedimentation on Bahamian slopes have numerous similarities as they have higher sedimentation rates during interglacials. At a small scale, every slope has its own characteristics that are contemporary controlled by two main characteristics: (a) facies on the adjacent shallow-water platform, and (b) the impact of shallow- and deep-water currents. Large-scale tectonics influence sediment deposition as it determines the position of the islands and impacts platform facies distribution.
{"title":"Sedimentology of Modern Bahamian Carbonate Slopes: Summary and Update","authors":"K. Fauquembergue, T. Mulder, J. Reijmer, V. Hanquiez, C. Betzler, E. Ducassou, A. Recouvreur, M. Principaud, J. Borgomano, S. Wilk, E. Poli","doi":"10.1029/2023GC011077","DOIUrl":"https://doi.org/10.1029/2023GC011077","url":null,"abstract":"<p>Slopes adjacent to the Bahamian carbonate platform revealed a large variety of depositional processes. In this study, we present a synthesis summarizing 109,000 km<sup>2</sup> of bathymetric and reflectivity data with ∼7,900 km of seismic lines and 311 m of sediment cores that were obtained over the last 50 years. These data are used to develop a conceptual model of sedimentation patterns on Quaternary carbonate slope systems and their interaction with the adjacent shallow-water carbonate platforms. Our data highlight that during the Quaternary, factors controlling large-scale sedimentation on Bahamian slopes have numerous similarities as they have higher sedimentation rates during interglacials. At a small scale, every slope has its own characteristics that are contemporary controlled by two main characteristics: (a) facies on the adjacent shallow-water platform, and (b) the impact of shallow- and deep-water currents. Large-scale tectonics influence sediment deposition as it determines the position of the islands and impacts platform facies distribution.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011077","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Traditionally, it is assumed that contributions of crust-derived CO2 emissions at arc settings are minor, but this requires well-constrained field studies to determine the extent of magma-carbonate reaction and concomitant C released. The Jurassic Bonanza arc on Vancouver Island (Canada) was built on a Triassic limestone platform and makes for an ideal setting to examine arc magma-carbonate interactions beneath an island arc. We examine how km-scale magma bodies might react with carbonate from a well-constrained study of a gabbro pluton that intrudes limestone. The pluton shows muted to nil carbonate interaction preserving primary igneous 87Sr/86Sr values (∼0.703) except for a thin (<2 m wide) marginal gabbro (∼0.706) in contact with a decarbonized metamorphic aureole. A lack of 87Sr/86Sr or δ18Ocpx enrichment in gabbro ∼10 to >1,000 m from the contact suggests that any reaction with limestone wallrock is limited to at most the outer ∼10 m of the pluton. More enhanced magma-carbonate interaction and CO2 production occurs via a network of shallow dikes and sills (<0.2 GPa) compared to deeper plutons, consistent with experimental data showing increased carbonate assimilation at shallower depths (≤0.5 GPa). Plutons are an important heat source to release CO2 from carbonate wallrock by contact metamorphism, where >89% of crust-derived CO2 is liberated by wallrock decarbonation and <11% is liberated by magma that assimilated limestone. Nonetheless, we show that neither magmatic nor metamorphic crust-derived CO2 contributions compare to mantle-derived CO2. Our study places realistic and quantitative limits on arc-derived CO2 from upper crustal limestone sources.
{"title":"Crust-Derived CO2 Production From a Shallow Pluton in Limestone Is Driven by Metamorphic Decarbonation, Not Assimilation","authors":"R. A. Morris, D. Canil","doi":"10.1029/2024GC011485","DOIUrl":"https://doi.org/10.1029/2024GC011485","url":null,"abstract":"<p>Traditionally, it is assumed that contributions of crust-derived CO<sub>2</sub> emissions at arc settings are minor, but this requires well-constrained field studies to determine the extent of magma-carbonate reaction and concomitant C released. The Jurassic Bonanza arc on Vancouver Island (Canada) was built on a Triassic limestone platform and makes for an ideal setting to examine arc magma-carbonate interactions beneath an island arc. We examine how km-scale magma bodies might react with carbonate from a well-constrained study of a gabbro pluton that intrudes limestone. The pluton shows muted to nil carbonate interaction preserving primary igneous <sup>87</sup>Sr/<sup>86</sup>Sr values (∼0.703) except for a thin (<2 m wide) marginal gabbro (∼0.706) in contact with a decarbonized metamorphic aureole. A lack of <sup>87</sup>Sr/<sup>86</sup>Sr or δ<sup>18</sup>O<sub>cpx</sub> enrichment in gabbro ∼10 to >1,000 m from the contact suggests that any reaction with limestone wallrock is limited to at most the outer ∼10 m of the pluton. More enhanced magma-carbonate interaction and CO<sub>2</sub> production occurs via a network of shallow dikes and sills (<0.2 GPa) compared to deeper plutons, consistent with experimental data showing increased carbonate assimilation at shallower depths (≤0.5 GPa). Plutons are an important heat source to release CO<sub>2</sub> from carbonate wallrock by contact metamorphism, where >89% of crust-derived CO<sub>2</sub> is liberated by wallrock decarbonation and <11% is liberated by magma that assimilated limestone. Nonetheless, we show that neither magmatic nor metamorphic crust-derived CO<sub>2</sub> contributions compare to mantle-derived CO<sub>2</sub>. Our study places realistic and quantitative limits on arc-derived CO<sub>2</sub> from upper crustal limestone sources.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011485","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. T. Halford, R. Karolytė, M. W. Andreason, B. Cathey, M. Cathey, J. T. Dellenbach, J. J. Cuzella, S. A. Sonnenberg, A. Cheng, K. J. W. McCaffrey, J. G. Gluyas, C. J. Ballentine
Natural gas fields with economic helium (>0.3 He %) require the radioactive decay of crustal uranium (U) and thorium (Th) to generate He and tectonic/structural regimes favorable to releasing and concentrating He. An unknown is determining the role of faults and structural features in focusing deep-seated He sources on shallow accumulations. We tested the correlation between high-He wells (n = 94) and structural features using a new high-resolution aeromagnetic survey in the Four Corners area, USA. A depth-to-basement map with basement lineaments/faults, an intrusion map, and a flattened basement structural high map were created using Werner deconvolution algorithms by combining magnetic, gravity, and topography data with magnetic and gravity depth profiles. We show quantitatively (via analysis of variance) that a non-random process controls the relationship between He (>0.3%) and both basement faults and intrusions: 88% of high-He wells occur <1 km of basement faults; and 85% of high-He wells occur <1 km of intrusions. As He % increases, the distance to the structural features decreases. Strong spatial/statistical correlations of He wells to both basement faults and intrusions suggest that advective transport via faults/intrusions facilitates He migration. The role of gas phase buoyancy and structural trapping is confirmed: 88% of high-He occurs within basement structural highs, and 91% of the remaining wells are <1 km from intrusions (potential structural high). We present a composite figure to illustrate how a probabilistic approach can be used as a predictive model to improve He exploration success by targeting zones of intersection of basement faults and intrusions within basement structural highs.
具有经济氦气(>0.3 He %)的天然气田需要地壳铀(U)和钍(Th)的放射性衰变来产生氦气,以及有利于释放和富集氦气的构造/结构体系。一个未知数是确定断层和构造特征在将深层氦源集中到浅层堆积中的作用。我们利用在美国四角地区进行的一项新的高分辨率航磁勘测,测试了高氦气井(n = 94)与构造特征之间的相关性。通过将磁力、重力和地形数据与磁力和重力深度剖面相结合,我们利用沃纳解卷积算法绘制了一张包含基底线状构造/断层的基底深度图、一张侵入图和一张扁平的基底构造高点图。我们从数量上(通过方差分析)表明,一个非随机过程控制着 He(>0.3%)与基底断层和侵入体之间的关系:88%的高He井出现在距基底断层<1 km处;85%的高He井出现在距侵入体<1 km处。随着He%的增加,与构造特征的距离也在减小。氦气井与基底断层和侵入体在空间/统计上的强相关性表明,通过断层/侵入体的平流输送促进了氦气的迁移。气相浮力和构造捕获的作用得到了证实:88%的高氦气发生在基底构造高点,其余91%的氦气井距离侵入体(潜在构造高点)<1千米。我们展示了一张综合图,说明如何利用概率方法作为预测模型,通过瞄准基底构造高点内的基底断层和侵入体交汇区,提高氦勘探的成功率。
{"title":"Probabilistic Determination of the Role of Faults and Intrusions in Helium-Rich Gas Fields Formation","authors":"D. T. Halford, R. Karolytė, M. W. Andreason, B. Cathey, M. Cathey, J. T. Dellenbach, J. J. Cuzella, S. A. Sonnenberg, A. Cheng, K. J. W. McCaffrey, J. G. Gluyas, C. J. Ballentine","doi":"10.1029/2024GC011522","DOIUrl":"https://doi.org/10.1029/2024GC011522","url":null,"abstract":"<p>Natural gas fields with economic helium (>0.3 He %) require the radioactive decay of crustal uranium (U) and thorium (Th) to generate He and tectonic/structural regimes favorable to releasing and concentrating He. An unknown is determining the role of faults and structural features in focusing deep-seated He sources on shallow accumulations. We tested the correlation between high-He wells (<i>n</i> = 94) and structural features using a new high-resolution aeromagnetic survey in the Four Corners area, USA. A depth-to-basement map with basement lineaments/faults, an intrusion map, and a flattened basement structural high map were created using Werner deconvolution algorithms by combining magnetic, gravity, and topography data with magnetic and gravity depth profiles. We show quantitatively (via analysis of variance) that a non-random process controls the relationship between He (>0.3%) and both basement faults and intrusions: 88% of high-He wells occur <1 km of basement faults; and 85% of high-He wells occur <1 km of intrusions. As He % increases, the distance to the structural features decreases. Strong spatial/statistical correlations of He wells to both basement faults and intrusions suggest that advective transport via faults/intrusions facilitates He migration. The role of gas phase buoyancy and structural trapping is confirmed: 88% of high-He occurs within basement structural highs, and 91% of the remaining wells are <1 km from intrusions (potential structural high). We present a composite figure to illustrate how a probabilistic approach can be used as a predictive model to improve He exploration success by targeting zones of intersection of basement faults and intrusions within basement structural highs.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011522","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141439623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Caroline Gini, John W. Jamieson, Eoghan P. Reeves, Amy Gartman, Thibaut Barreyre, Michael G. Babechuk, Steffen L. Jørgensen, Katleen Robert
The recently discovered Fåvne vent field, located at 3,040 m depth on the slow-spreading Mohns mid-ocean ridge between Greenland and Norway, is a high-temperature (≥250°C) vent field that is characterized by Fe oxyhydroxide-rich and S-poor chimneys and mounds. The vent field is located on both the hanging wall and footwall of a normal fault with a ∼1.5 km throw that forms the western edge of the ∼20 km wide ridge axial valley. Data collected during exploration of the site using a remotely operated vehicle as well as mineralogical and geochemical analyses of rock samples and sediments are used to characterize the geological setting of the vent field and composition of the hydrothermal deposits. The chimney walls are highly porous and lack defined chalcopyrite lined conduits, typical of high-temperature chimneys. Overall, abundant Fe oxyhydroxide precipitation at high-temperature vents at Fåvne reflects an excess of Fe over reduced S in the fluid, leading to precipitation of Fe oxide and oxyhydroxide minerals at high to moderate temperature vents (>100°C), and as microbially mediated and abiotic precipitation of Fe oxyhydroxide minerals at low-temperature diffuse vents (<100°C). The mounds and chimneys exhibit low base metal and reduced S concentrations relative to globally averaged seafloor deposits and suggest subseafloor mixing of hydrothermal fluid with seawater, causing metal sulfide precipitation. Cobalt enrichment at Fåvne may reflect a subsurface influence of an ultramafic substrate on circulating fluids, although ultramafic rocks are absent on the seafloor and no other elements typical of ultramafic deposits are present.
最近发现的 Fåvne 喷口区位于格陵兰和挪威之间缓慢扩张的莫恩斯洋中脊上 3,040 米深处,是一个高温(≥250°C)喷口区,其特征是富含氢氧化铁和贫S的烟囱和土丘。喷口区位于一个正断层的悬壁和底壁,正断层的走向≥1.5千米,构成了≥20千米宽的山脊轴谷的西部边缘。利用遥控潜水器对该地点进行勘探时收集的数据,以及对岩石样本和沉积物进行的矿物学和地球化学分析,用于描述喷口区的地质环境和热液沉积物的成分。烟囱壁孔隙很大,缺乏明确的黄铜矿内衬导管,这是高温烟囱的典型特征。总的来说,法文高温喷口大量的氢氧化铁沉淀反映了流体中铁的含量超过了还原性S,导致氧化铁和氢氧化铁矿物在高温至中温喷口(100°C)沉淀,以及在低温扩散喷口(100°C)微生物介导和非生物沉淀的氢氧化铁矿物。与全球平均海底沉积物相比,土丘和烟囱显示出较低的贱金属浓度和较低的 S 浓度,表明热液与海水在海底下混合,导致金属硫化物沉淀。尽管海底没有超基性岩,也没有超基性岩沉积物所特有的其他元素,但法文的钴富集可能反映了超基性岩基质对循环流体的影响。
{"title":"Iron Oxyhydroxide-Rich Hydrothermal Deposits at the High-Temperature Fåvne Vent Field, Mohns Ridge","authors":"Caroline Gini, John W. Jamieson, Eoghan P. Reeves, Amy Gartman, Thibaut Barreyre, Michael G. Babechuk, Steffen L. Jørgensen, Katleen Robert","doi":"10.1029/2024GC011481","DOIUrl":"https://doi.org/10.1029/2024GC011481","url":null,"abstract":"<p>The recently discovered Fåvne vent field, located at 3,040 m depth on the slow-spreading Mohns mid-ocean ridge between Greenland and Norway, is a high-temperature (≥250°C) vent field that is characterized by Fe oxyhydroxide-rich and S-poor chimneys and mounds. The vent field is located on both the hanging wall and footwall of a normal fault with a ∼1.5 km throw that forms the western edge of the ∼20 km wide ridge axial valley. Data collected during exploration of the site using a remotely operated vehicle as well as mineralogical and geochemical analyses of rock samples and sediments are used to characterize the geological setting of the vent field and composition of the hydrothermal deposits. The chimney walls are highly porous and lack defined chalcopyrite lined conduits, typical of high-temperature chimneys. Overall, abundant Fe oxyhydroxide precipitation at high-temperature vents at Fåvne reflects an excess of Fe over reduced S in the fluid, leading to precipitation of Fe oxide and oxyhydroxide minerals at high to moderate temperature vents (>100°C), and as microbially mediated and abiotic precipitation of Fe oxyhydroxide minerals at low-temperature diffuse vents (<100°C). The mounds and chimneys exhibit low base metal and reduced S concentrations relative to globally averaged seafloor deposits and suggest subseafloor mixing of hydrothermal fluid with seawater, causing metal sulfide precipitation. Cobalt enrichment at Fåvne may reflect a subsurface influence of an ultramafic substrate on circulating fluids, although ultramafic rocks are absent on the seafloor and no other elements typical of ultramafic deposits are present.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011481","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141439624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Simon A. Hunt, Andrew M. Walker, Oliver T. Lord, Stephen Stackhouse, Lewis Schardong, Lora S. Armstrong, Andrew J. Parsons, Geoffrey E. Lloyd, John Wheeler, Danielle M. Fenech, Stefan Michalik, Matthew L. Whitaker
Seismic observations show the Earth's inner core has significant and unexplained variation in seismic attenuation with position, depth and direction. Interpreting these observations is difficult without knowledge of the visco- or anelastic dissipation processes active in iron under inner core conditions. Here, a previously unconsidered attenuation mechanism is observed in zinc, a low pressure analog of hcp-iron, during small strain sinusoidal deformation experiments. The experiments were performed in a deformation-DIA combined with X-radiography, at seismic frequencies (∼0.003–0.1 Hz), high pressure and temperatures up to ∼80% of melting temperature. Significant dissipation (0.077 ≤ Q−1(ω) ≤ 0.488) is observed along with frequency dependent softening of zinc's Young's modulus and an extremely small activation energy for creep (⩽7 kJ mol−1). In addition, during sinusoidal deformation the original microstructure is replaced by one with a reduced dislocation density and small, uniform, grain size. This combination of behavior collectively reflects a mode of deformation called “internal stress superplasticity”; this deformation mechanism is unique to anisotropic materials and activated by cyclic loading generating large internal stresses. Here we observe a new form of internal stress superplasticity, which we name as “elastic strain mismatch superplasticity.” In it the large stresses are caused by the compressional anisotropy. If this mechanism is also active in hcp-iron and the Earth's inner-core it will be a contributor to inner-core observed seismic attenuation and constrain the maximum inner-core grain-size to ≲10 km.
{"title":"Experimental Observation of a New Attenuation Mechanism in hcp-Metals That May Operate in the Earth's Inner Core","authors":"Simon A. Hunt, Andrew M. Walker, Oliver T. Lord, Stephen Stackhouse, Lewis Schardong, Lora S. Armstrong, Andrew J. Parsons, Geoffrey E. Lloyd, John Wheeler, Danielle M. Fenech, Stefan Michalik, Matthew L. Whitaker","doi":"10.1029/2023GC011386","DOIUrl":"https://doi.org/10.1029/2023GC011386","url":null,"abstract":"<p>Seismic observations show the Earth's inner core has significant and unexplained variation in seismic attenuation with position, depth and direction. Interpreting these observations is difficult without knowledge of the visco- or anelastic dissipation processes active in iron under inner core conditions. Here, a previously unconsidered attenuation mechanism is observed in zinc, a low pressure analog of <i>hcp</i>-iron, during small strain sinusoidal deformation experiments. The experiments were performed in a deformation-DIA combined with X-radiography, at seismic frequencies (∼0.003–0.1 Hz), high pressure and temperatures up to ∼80% of melting temperature. Significant dissipation (0.077 ≤ <i>Q</i><sup>−1</sup>(<i>ω</i>) ≤ 0.488) is observed along with frequency dependent softening of zinc's Young's modulus and an extremely small activation energy for creep (⩽7 kJ mol<sup>−1</sup>). In addition, during sinusoidal deformation the original microstructure is replaced by one with a reduced dislocation density and small, uniform, grain size. This combination of behavior collectively reflects a mode of deformation called “internal stress superplasticity”; this deformation mechanism is unique to anisotropic materials and activated by cyclic loading generating large internal stresses. Here we observe a new form of internal stress superplasticity, which we name as “<i>elastic strain mismatch superplasticity</i>.” In it the large stresses are caused by the compressional anisotropy. If this mechanism is also active in <i>hcp</i>-iron and the Earth's inner-core it will be a contributor to inner-core observed seismic attenuation and constrain the maximum inner-core grain-size to ≲10 km.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011386","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141441375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Björn H. Heyn, Grace E. Shephard, Clinton P. Conrad
The widespread High Arctic Large Igneous Province (HALIP) exhibits prolonged melting over more than 50 Myr, an observation that is difficult to reconcile with the classic view that large igneous provinces (LIPs) originate from melting in plume heads. Hence, the suggested plume-related origin and classification of HALIP as a LIP have been questioned. Here, we use numerical models that include melting and melt migration to investigate a rising plume interacting with lithosphere of variable thickness, that is, a basin-to-craton setting applicable to the Arctic. Models reveal that melt migration introduces significant spatial and temporal variations in melt volumes and pulses of melt production, including protracted melting for at least about 30–40 Myr, because of the dynamic feedback between migrating melt and local lithosphere thinning. For HALIP, plume material deflected from underneath the Greenland craton can re-activate melting zones below the previously plume-influenced Sverdrup Basin after a melt-free period of about 10–15 Myr, even though the plume is already ∼500 km away. Hence, actively melting zones do not necessarily represent the location of the deeper plume stem at a given time, especially for secondary pulses. Additional processes such as (minor) plume flux variations or local lithospheric extension may alter the timing and volume of HALIP pulses, but are to first order not required to reproduce the long-lived and multi-pulse magmatism of HALIP. Since melting zones are always plume-fed, we would expect HALIP magmatism to exhibit plume-related trace element signatures throughout time, potentially shifting from mostly tholeiitic toward more alkalic compositions.
{"title":"Prolonged Multi-Phase Magmatism Due To Plume-Lithosphere Interaction as Applied to the High Arctic Large Igneous Province","authors":"Björn H. Heyn, Grace E. Shephard, Clinton P. Conrad","doi":"10.1029/2023GC011380","DOIUrl":"https://doi.org/10.1029/2023GC011380","url":null,"abstract":"<p>The widespread High Arctic Large Igneous Province (HALIP) exhibits prolonged melting over more than 50 Myr, an observation that is difficult to reconcile with the classic view that large igneous provinces (LIPs) originate from melting in plume heads. Hence, the suggested plume-related origin and classification of HALIP as a LIP have been questioned. Here, we use numerical models that include melting and melt migration to investigate a rising plume interacting with lithosphere of variable thickness, that is, a basin-to-craton setting applicable to the Arctic. Models reveal that melt migration introduces significant spatial and temporal variations in melt volumes and pulses of melt production, including protracted melting for at least about 30–40 Myr, because of the dynamic feedback between migrating melt and local lithosphere thinning. For HALIP, plume material deflected from underneath the Greenland craton can re-activate melting zones below the previously plume-influenced Sverdrup Basin after a melt-free period of about 10–15 Myr, even though the plume is already ∼500 km away. Hence, actively melting zones do not necessarily represent the location of the deeper plume stem at a given time, especially for secondary pulses. Additional processes such as (minor) plume flux variations or local lithospheric extension may alter the timing and volume of HALIP pulses, but are to first order not required to reproduce the long-lived and multi-pulse magmatism of HALIP. Since melting zones are always plume-fed, we would expect HALIP magmatism to exhibit plume-related trace element signatures throughout time, potentially shifting from mostly tholeiitic toward more alkalic compositions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011380","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141435655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dongmei Tang, Kezhang Qin, Noreen J. Evans, Haoru Wang
Copper and iron isotopic signatures in sulfide and silicate minerals are important genetic indicators in magmatic sulfide deposits. Kalatongke is a large-scale magmatic Cu-Ni sulfide deposit in the Central Asian Orogenic Belt, and one that experienced multiple stages of magmatism and contamination. It is an ideal deposit in which to study Cu-Fe isotopic fractionation during multiple stages of magmatism and sulfide mineralization processes. The Kalatongke sulfide orebodies are hosted by three small mafic intrusions in which pyroxene and sulfides (pyrrhotite, pentlandite, and chalcopyrite) are the most common Fe-rich minerals, and chalcopyrite is the dominant Cu-rich mineral. Sulfide liquid and silicate melt ▵56FeSul-Sil (0.03–0.19‰) and ▵65CuCcp-Sil (−0.78–0.74‰) values are indicative of non-equilibrium fractionation. Most of the Cu isotope compositions in the sulfide ores at Kalatongke can be modeled as subduction- metasomatized, oxidized mantle source-derived silicate melt (initial δ57Fe = 0.15‰, δ65Cu = −0.07‰) that underwent lower crustal contamination, and then reacted with silicate melt, having an R factor of 100–1,000. Rapid silicate melt and sulfide liquid Fe isotope exchange and re-equilibration between chalcopyrite and pyrrhotite in the massive ores is reflected in the similarity of their δ56Fe values. Sulfide in disseminated ores shows a range of Fe isotope ratios, influenced by the proportions of monosulfide solid solution (MSS) and intermediate solid solution (ISS) formed. Copper isotopes can be utilized to characterize crustal contamination and silicate melt-sulfide liquid interaction, while the Fe isotope ratios of sulfide minerals record sulfide liquid segregation and evolution in magmatic sulfide deposits.
{"title":"Sulfide Copper-Iron Isotopic Fractionation During Formation of the Kalatongke Magmatic Cu-Ni Sulfide Deposit in the Central Asian Orogenic Belt","authors":"Dongmei Tang, Kezhang Qin, Noreen J. Evans, Haoru Wang","doi":"10.1029/2023GC011406","DOIUrl":"https://doi.org/10.1029/2023GC011406","url":null,"abstract":"<p>Copper and iron isotopic signatures in sulfide and silicate minerals are important genetic indicators in magmatic sulfide deposits. Kalatongke is a large-scale magmatic Cu-Ni sulfide deposit in the Central Asian Orogenic Belt, and one that experienced multiple stages of magmatism and contamination. It is an ideal deposit in which to study Cu-Fe isotopic fractionation during multiple stages of magmatism and sulfide mineralization processes. The Kalatongke sulfide orebodies are hosted by three small mafic intrusions in which pyroxene and sulfides (pyrrhotite, pentlandite, and chalcopyrite) are the most common Fe-rich minerals, and chalcopyrite is the dominant Cu-rich mineral. Sulfide liquid and silicate melt ▵<sup>56</sup>Fe<sub>Sul-Sil</sub> (0.03–0.19‰) and ▵<sup>65</sup>Cu<sub>Ccp-Sil</sub> (−0.78–0.74‰) values are indicative of non-equilibrium fractionation. Most of the Cu isotope compositions in the sulfide ores at Kalatongke can be modeled as subduction- metasomatized, oxidized mantle source-derived silicate melt (initial δ<sup>57</sup>Fe = 0.15‰, δ<sup>65</sup>Cu = −0.07‰) that underwent lower crustal contamination, and then reacted with silicate melt, having an R factor of 100–1,000. Rapid silicate melt and sulfide liquid Fe isotope exchange and re-equilibration between chalcopyrite and pyrrhotite in the massive ores is reflected in the similarity of their δ<sup>56</sup>Fe values. Sulfide in disseminated ores shows a range of Fe isotope ratios, influenced by the proportions of monosulfide solid solution (MSS) and intermediate solid solution (ISS) formed. Copper isotopes can be utilized to characterize crustal contamination and silicate melt-sulfide liquid interaction, while the Fe isotope ratios of sulfide minerals record sulfide liquid segregation and evolution in magmatic sulfide deposits.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011406","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141425000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xinzhuan Guo, Bo Feng, Baohua Zhang, Shuangmeng Zhai, Weihong Xue, Yunke Song, Yuping Song, Xinxin Yan
The thermal properties of major minerals play a key role in understanding the internal dynamic mechanism and thermal evolution of the Earth and rocky planets. In this study, we first investigated the effect of Fe on the thermal conductivity (κ) and the thermal diffusivity (D) of orthopyroxene at 1–3 GPa and 293–873 K by the transient plane source method. The κ and D both decrease with increasing temperature and decreasing pressure. With increasing Fe content, the two parameters both quickly decrease from the beginning and then slack off. We further modeled the thermal evolution of S-type asteroids, which strongly depends on the composition model and the dimension of the planet. Combining the present data with surface heat flow and heat production, the lunar's geotherm until 1,400 km is constructed. The core-mantle boundary temperature of the Moon is refined from 1,883 to 1,754 K.
主要矿物的热性质对于理解地球和岩质行星的内部动力机制和热演化起着关键作用。在本研究中,我们首先通过瞬态平面源方法研究了正长石在 1-3 GPa 和 293-873 K 条件下铁对其热导率(κ)和热扩散率(D)的影响。κ和D均随温度升高和压力降低而减小。随着铁含量的增加,这两个参数都从一开始迅速降低,然后逐渐减小。我们进一步建立了 S 型小行星的热演化模型,它与行星的成分模型和尺寸密切相关。结合目前的数据和地表热流与产热,我们构建了 1400 公里以内的月球地热。月球的地核-地幔边界温度从 1,883 千卡细化到 1,754 千卡。
{"title":"Effect of Iron Content on the Thermal Conductivity and Thermal Diffusivity of Orthopyroxene","authors":"Xinzhuan Guo, Bo Feng, Baohua Zhang, Shuangmeng Zhai, Weihong Xue, Yunke Song, Yuping Song, Xinxin Yan","doi":"10.1029/2023GC011419","DOIUrl":"https://doi.org/10.1029/2023GC011419","url":null,"abstract":"<p>The thermal properties of major minerals play a key role in understanding the internal dynamic mechanism and thermal evolution of the Earth and rocky planets. In this study, we first investigated the effect of Fe on the thermal conductivity (<i>κ</i>) and the thermal diffusivity (<i>D</i>) of orthopyroxene at 1–3 GPa and 293–873 K by the transient plane source method. The <i>κ</i> and <i>D</i> both decrease with increasing temperature and decreasing pressure. With increasing Fe content, the two parameters both quickly decrease from the beginning and then slack off. We further modeled the thermal evolution of S-type asteroids, which strongly depends on the composition model and the dimension of the planet. Combining the present data with surface heat flow and heat production, the lunar's geotherm until 1,400 km is constructed. The core-mantle boundary temperature of the Moon is refined from 1,883 to 1,754 K.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GC011419","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141424884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. E. Aguirre Palafox, A. Möller, N. M. McLean, G. A. Ludvigson, C. E. Colombi, I. P. Montañez
This study investigates the potential of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating for carbonate nodules in the Late Triassic Ischigualasto Formation of northwestern Argentina. We establish a fully characterized paragenetic sequence to guide the analysis of three pedogenic carbonates and compare the U-Pb ages with published geochronology from volcanic ashes within the sedimentary succession. Our findings demonstrate the importance of interpreting U-Pb data within a well-defined paragenetic framework for accurate age interpretation of pedogenic carbonates. We observe variations in U-Pb isotopic signatures across different generations of carbonate precipitates and identify syn-pedogenic and early burial calcite cements as most suitable for precise dating. Respectively, these two calcite cements are interpreted as microcodium and crack-lining calcite cements formed early in the paragenetic sequence during pedogenesis to early burial of the paleosols as they transitioned from the unsaturated vadose to saturated phreatic zone below the water table. The U-Pb ages obtained from the carbonate nodules agree with the radioisotopic ages of volcanic ashes, supporting the validity of our dating strategy. These results contribute to advancing U-Pb carbonate geochronology and highlight its increased potential for dating sedimentary records in the terrestrial realm. Future research should focus on replicating similar work on different carbonate nodules within the Ischigualasto Fm and expanding the application of LA-ICP-MS U-Pb dating to other carbonate-bearing formations, especially in successions with limited absolute ages or where volcanic ashes are sparse or absent.
{"title":"U-Pb Geochronology of Paleosol Carbonate Cements by LA-ICP-MS: A Proof of Concept and Strategy for Dating the Terrestrial Record","authors":"L. E. Aguirre Palafox, A. Möller, N. M. McLean, G. A. Ludvigson, C. E. Colombi, I. P. Montañez","doi":"10.1029/2024GC011488","DOIUrl":"https://doi.org/10.1029/2024GC011488","url":null,"abstract":"<p>This study investigates the potential of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating for carbonate nodules in the Late Triassic Ischigualasto Formation of northwestern Argentina. We establish a fully characterized paragenetic sequence to guide the analysis of three pedogenic carbonates and compare the U-Pb ages with published geochronology from volcanic ashes within the sedimentary succession. Our findings demonstrate the importance of interpreting U-Pb data within a well-defined paragenetic framework for accurate age interpretation of pedogenic carbonates. We observe variations in U-Pb isotopic signatures across different generations of carbonate precipitates and identify syn-pedogenic and early burial calcite cements as most suitable for precise dating. Respectively, these two calcite cements are interpreted as microcodium and crack-lining calcite cements formed early in the paragenetic sequence during pedogenesis to early burial of the paleosols as they transitioned from the unsaturated vadose to saturated phreatic zone below the water table. The U-Pb ages obtained from the carbonate nodules agree with the radioisotopic ages of volcanic ashes, supporting the validity of our dating strategy. These results contribute to advancing U-Pb carbonate geochronology and highlight its increased potential for dating sedimentary records in the terrestrial realm. Future research should focus on replicating similar work on different carbonate nodules within the Ischigualasto Fm and expanding the application of LA-ICP-MS U-Pb dating to other carbonate-bearing formations, especially in successions with limited absolute ages or where volcanic ashes are sparse or absent.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011488","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141424820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Generic Mapping Tools (GMT) is a well-known set of software originally developed for geosciences, allowing scientists in climate and solid earth disciplines to routinely create publish-ready maps and graphics. However, GMT users rarely make animations despite their undeniable benefit for understanding and teaching dynamic processes. As reading habits shift from print to digital, capitalizing on animations for illustrating scientific concepts is more accessible than ever. In the latest GMT version (6.5), we have added and refined the movie-making modules, alleviating the time-consuming steps that would hinder GMT users from making such animations. In this paper, we will explain how GMT's “movie” module works and provide six representative examples, from basic to more advanced, to show some of its key features. We hope our presentation will encourage the masses to routinely create animations for their publications.
{"title":"The Generic Mapping Tools and Animations for the Masses","authors":"P. Wessel, F. Esteban, G. Delaviel-Anger","doi":"10.1029/2024GC011545","DOIUrl":"https://doi.org/10.1029/2024GC011545","url":null,"abstract":"<p>Generic Mapping Tools (GMT) is a well-known set of software originally developed for geosciences, allowing scientists in climate and solid earth disciplines to routinely create publish-ready maps and graphics. However, GMT users rarely make animations despite their undeniable benefit for understanding and teaching dynamic processes. As reading habits shift from print to digital, capitalizing on animations for illustrating scientific concepts is more accessible than ever. In the latest GMT version (6.5), we have added and refined the movie-making modules, alleviating the time-consuming steps that would hinder GMT users from making such animations. In this paper, we will explain how GMT's “movie” module works and provide six representative examples, from basic to more advanced, to show some of its key features. We hope our presentation will encourage the masses to routinely create animations for their publications.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011545","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141424821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}