M. Vigorito, A. Hurst, A. Scott, Olivier Stanzione, A. Grippa
Giant sand injection complexes form, intricate, basin-scale fluid plumbing systems and document the remobilisation and intrusion of several tens of cubic kilometres of sand within the shallow crust in stratigraphic units 100's metres thick. This is the first detailed and extensive account of the Panoche Giant Injection Complex (PGIG), a regionally significant outcrop (>300 km2) and part of a larger subsurface development (>4000 km2) identified in boreholes and on seismic reflection data. Magnificent exposure of the PGIC occurs along the north western margin of the San Joaquin Valley and presents the opportunity to examine the regional geological significance of a giant sand injection complex and its origin in the context of a late Cretaceous – early Paleocene forearc basin. Between 25 and 49 km3 of sand were remobilised and injected, at least 0.35 km3 of which extruded onto the paleo-seafloor. Large sandstone intrusions often >10 m thick and laterally extensive on a kilometer scale formed saucer-shaped intrusions, wing-like intrusions and a variety of sill geometries along with volumetrically smaller randomly oriented dikes in a 200–300 m thick interval. Dikes prevail below and above this interval, some reaching the paleo seafloor and extruding sand. Networks of propagating hydrofractures form intensely brecciated host strata, some of which were intruded by sand. All intrusions formed in a single pulsed event in which the most intense hydrofracturing caused by supra-lithostatic fluid pressure occurred approximately 600 to 800 m below the paleo seafloor. A crudely orthogonal arrangement of dikes is preserved with most oriented normal, and less commonly oriented parallel to the oceanic trench associated with the late Mesozoic to early Tertiary North Pacific subduction. Dikes orthogonal to the trench opened against the minimum horizontal stress, which was parallel to the trench. Dikes parallel to the trench opened against the regional maximum horizontal stress along minor faults formed in extension caused by shallow crustal deformation. There is no evidence that compressional tectonics influenced the onset of elevated pore fluid pressure necessary to promote sand injection. However, tectonic compression was responsible for creating the basin physiography that locally increased subsidence and accelerated chemical diagenesis in the basin centre. PGIC outcrop, located along the basin margins, was unlikely to have experienced heating above 70 °C, equivalent about 2 km burial, so the effects of chemical diagenesis in the host strata of the injection complex had negligible potential to evolve significant pore water volume. In a deeper part of the basin approximately 150 km to the south, lateral equivalents of the host strata were subjected to heating >100 °C and would expel significant volumes of water displaced by quartz cementation and clay dehydration that caused lateral pressure transfer to the north and western margin of the basin where the PGIC form
{"title":"A giant sand injection complex: Processes and implications for basin evolution and subsurface fluid flow","authors":"M. Vigorito, A. Hurst, A. Scott, Olivier Stanzione, A. Grippa","doi":"10.2475/06.2022.01","DOIUrl":"https://doi.org/10.2475/06.2022.01","url":null,"abstract":"Giant sand injection complexes form, intricate, basin-scale fluid plumbing systems and document the remobilisation and intrusion of several tens of cubic kilometres of sand within the shallow crust in stratigraphic units 100's metres thick. This is the first detailed and extensive account of the Panoche Giant Injection Complex (PGIG), a regionally significant outcrop (>300 km2) and part of a larger subsurface development (>4000 km2) identified in boreholes and on seismic reflection data. Magnificent exposure of the PGIC occurs along the north western margin of the San Joaquin Valley and presents the opportunity to examine the regional geological significance of a giant sand injection complex and its origin in the context of a late Cretaceous – early Paleocene forearc basin. Between 25 and 49 km3 of sand were remobilised and injected, at least 0.35 km3 of which extruded onto the paleo-seafloor. Large sandstone intrusions often >10 m thick and laterally extensive on a kilometer scale formed saucer-shaped intrusions, wing-like intrusions and a variety of sill geometries along with volumetrically smaller randomly oriented dikes in a 200–300 m thick interval. Dikes prevail below and above this interval, some reaching the paleo seafloor and extruding sand. Networks of propagating hydrofractures form intensely brecciated host strata, some of which were intruded by sand. All intrusions formed in a single pulsed event in which the most intense hydrofracturing caused by supra-lithostatic fluid pressure occurred approximately 600 to 800 m below the paleo seafloor. A crudely orthogonal arrangement of dikes is preserved with most oriented normal, and less commonly oriented parallel to the oceanic trench associated with the late Mesozoic to early Tertiary North Pacific subduction. Dikes orthogonal to the trench opened against the minimum horizontal stress, which was parallel to the trench. Dikes parallel to the trench opened against the regional maximum horizontal stress along minor faults formed in extension caused by shallow crustal deformation. There is no evidence that compressional tectonics influenced the onset of elevated pore fluid pressure necessary to promote sand injection. However, tectonic compression was responsible for creating the basin physiography that locally increased subsidence and accelerated chemical diagenesis in the basin centre. PGIC outcrop, located along the basin margins, was unlikely to have experienced heating above 70 °C, equivalent about 2 km burial, so the effects of chemical diagenesis in the host strata of the injection complex had negligible potential to evolve significant pore water volume. In a deeper part of the basin approximately 150 km to the south, lateral equivalents of the host strata were subjected to heating >100 °C and would expel significant volumes of water displaced by quartz cementation and clay dehydration that caused lateral pressure transfer to the north and western margin of the basin where the PGIC form","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43318231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alkaline, alkaline earth, many 3d and most 4f modifier oxides dissolved in siliceous melts mix non-ideally with SiO2 to produce linear, density-compositional mixing trends from which partial molar volumes of modifier oxides (V*) are determined. An analysis of these experimental data reveals that the partial molar volumes of alkali, alkaline earths, most 4f and many 3d modifier oxides partial molar volumes are accurately reproduced by: where FC = (z+•z−)/d2 (Coulomb's Law) and z indicates charge. The bond length ‘d’ is the sum of the radii of the cation (M+, M2+, M3+ or M4+) and oxide ion (O2−) observed in ionic crystals. The coefficients ‘m’ and ‘b’ are 0.325 and 1.38 Å/atom respectively. Partial molar volumes of network-forming oxides also conform to the above equation where ‘m’ = ∼3.25 and ‘b’ is 1.68 Å/atom. Coulomb's force of attraction (FC) is the product of the cationic field strength (z+/d2) and the charge on an anion, where ‘d’ is the distance separating the centers of the two charges. In silicate melts containing modifier cations, apical O atoms of Si tetrahedra are negatively charged and are displaced toward the cations due to Coulombic attraction. The resulting collapse around the cations is referred to as ‘electrostriction’. Partial molar volumes (V*) of modifier oxides are thus composed of two terms, the volume of the polyhedron of the modifier cation (VPoly) and a volume associated with collapse of tetrahedra around the cation (VCol): VCol is negative for all modifier oxides and becomes increasingly negative with increased charge on the cation and with increased coordination number (CN). VPoly is itself composed of two terms, an intrinsic volume (VInt) and an excluded volume (VEx). The intrinsic volume can be calculated using cationic and O2− radii evaluated from ionic crystals. VEx reflects the state of packing around cationic polyhedra. It is equal to 6.83 Å3/atom for all modifier oxides so that the expression for VPoly is: A linear relationship exists between VPoly and VCol which results in the observed linear density-composition trends from which partial molar volumes are determined. In spite of their linearity, these trends are the result of non-ideal mixing of modifier oxide and SiO2 components in siliceous melts. Our finding that tetrahedra collapse around modifier cations differs from the traditional perspective where modifier cations were considered to occupy voids within the silicate network but otherwise had limited effect on melt structure. These results demonstrate that modifier cations affect the network substantially by causing surrounding tetrahedra to rotate, twist, tilt and flex during their collapse toward modifier cations.
溶解在硅质熔体中的碱性、碱性土、许多3d和大多数4f改性剂氧化物与SiO2非理想混合，产生线性、密度-成分混合趋势，由此确定改性剂氧化物的偏摩尔体积(V*)。对这些实验数据的分析表明，碱、碱土、大多数4f和许多三维改性氧化物的偏摩尔体积可以通过:精确地再现，其中FC = (z+•z−)/d2(库仑定律)，z表示电荷。键长' d '是离子晶体中观察到的阳离子(M+， M2+， M3+或M4+)和氧化离子(O2−)的半径之和。系数m和b分别为0.325和1.38 Å/atom。形成网络的氧化物的偏摩尔体积也符合上述方程，其中' m ' = ~ 3.25， ' b ' = 1.68 Å/原子。库仑引力(FC)是阳离子场强(z+/d2)和阴离子上的电荷的乘积，其中d是两个电荷中心之间的距离。在含有改性阳离子的硅酸盐熔体中，硅四面体的顶端O原子带负电荷，并由于库仑吸引而向阳离子偏移。在阳离子周围产生的坍塌被称为“电致伸缩”。因此，改性剂氧化物的偏摩尔体积(V*)由两项组成，即改性剂阳离子多面体的体积(VPoly)和与阳离子周围四面体坍塌相关的体积(VCol): VCol对所有改性剂氧化物都是负的，并且随着阳离子上电荷的增加和配位数(CN)的增加而变得越来越负。VPoly本身由两项组成，固有体积(VInt)和排除体积(VEx)。本征体积可以通过离子晶体的阳离子半径和O2−半径来计算。VEx反映了阳离子多面体周围的堆积状态。对于所有的改性氧化物都等于6.83 Å3/原子，因此VPoly的表达式为:VPoly和VCol之间存在线性关系，这导致了观察到的线性密度组成趋势，由此确定了部分摩尔体积。尽管它们呈线性，但这些趋势是硅质熔体中改性剂氧化物和SiO2组分不理想混合的结果。我们发现四面体在改性剂阳离子周围坍塌，这与传统观点不同，传统观点认为改性剂阳离子占据硅酸盐网络中的空隙，但对熔体结构的影响有限。这些结果表明，改性剂阳离子通过引起周围四面体在向改性剂阳离子坍塌过程中旋转、扭曲、倾斜和弯曲，从而对网络产生实质性的影响。
{"title":"Partial molar volumes of metal oxides in silicate melts: Effects of Coulombic interactions","authors":"H. Nesbitt, P. Richet, G. Bancroft, G. Henderson","doi":"10.2475/05.2022.02","DOIUrl":"https://doi.org/10.2475/05.2022.02","url":null,"abstract":"Alkaline, alkaline earth, many 3d and most 4f modifier oxides dissolved in siliceous melts mix non-ideally with SiO2 to produce linear, density-compositional mixing trends from which partial molar volumes of modifier oxides (V*) are determined. An analysis of these experimental data reveals that the partial molar volumes of alkali, alkaline earths, most 4f and many 3d modifier oxides partial molar volumes are accurately reproduced by: where FC = (z+•z−)/d2 (Coulomb's Law) and z indicates charge. The bond length ‘d’ is the sum of the radii of the cation (M+, M2+, M3+ or M4+) and oxide ion (O2−) observed in ionic crystals. The coefficients ‘m’ and ‘b’ are 0.325 and 1.38 Å/atom respectively. Partial molar volumes of network-forming oxides also conform to the above equation where ‘m’ = ∼3.25 and ‘b’ is 1.68 Å/atom. Coulomb's force of attraction (FC) is the product of the cationic field strength (z+/d2) and the charge on an anion, where ‘d’ is the distance separating the centers of the two charges. In silicate melts containing modifier cations, apical O atoms of Si tetrahedra are negatively charged and are displaced toward the cations due to Coulombic attraction. The resulting collapse around the cations is referred to as ‘electrostriction’. Partial molar volumes (V*) of modifier oxides are thus composed of two terms, the volume of the polyhedron of the modifier cation (VPoly) and a volume associated with collapse of tetrahedra around the cation (VCol): VCol is negative for all modifier oxides and becomes increasingly negative with increased charge on the cation and with increased coordination number (CN). VPoly is itself composed of two terms, an intrinsic volume (VInt) and an excluded volume (VEx). The intrinsic volume can be calculated using cationic and O2− radii evaluated from ionic crystals. VEx reflects the state of packing around cationic polyhedra. It is equal to 6.83 Å3/atom for all modifier oxides so that the expression for VPoly is: A linear relationship exists between VPoly and VCol which results in the observed linear density-composition trends from which partial molar volumes are determined. In spite of their linearity, these trends are the result of non-ideal mixing of modifier oxide and SiO2 components in siliceous melts. Our finding that tetrahedra collapse around modifier cations differs from the traditional perspective where modifier cations were considered to occupy voids within the silicate network but otherwise had limited effect on melt structure. These results demonstrate that modifier cations affect the network substantially by causing surrounding tetrahedra to rotate, twist, tilt and flex during their collapse toward modifier cations.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46402195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lithium isotopes have emerged as a powerful tool to probe the response of global weathering to changes in climate. Due to the preferential incorporation of 6Li into clay minerals during chemical weathering, the isotope ratio δ7Li may be used to interrogate the balance of primary mineral dissolution and clay precipitation. This balance has been linked to relative rates of chemical and physical denudation, such that dissolved δ7Li (δ7Lidiss) is highest at moderate weathering intensities when chemical and physical denudation are comparable. However, we argue that current theory linking δ7Li to weathering regimes through fluid travel times are unable to explain observations of low δ7Li and high Li concentrations in rapidly eroding settings. In this study, we re-examine the relationships between δ7Li, Li concentration, and weathering regime by incorporating Li isotopes into simulations of weathering profiles using a reactive transport model (CrunchFlow) that includes advective fluxes of regolith to simulate variable erosion rates in response to uplift. In these simulations, fractionation is implemented through a kinetic fractionation factor during clay precipitation, which allows the δ7Li of dissolved and suspended loads in the model to vary as a function of Li/Al ratios in primary and secondary minerals. When the model is run over a range of infiltration and erosion rates, simulations reproduce observed global patterns of δ7Lidiss and suspended load δ7Li as a function of weathering intensity, controlled primarily by water travel times and mineral residence times in weathered bedrock. We find that reduced water travel times at low weathering intensity, however, are inconsistent with observations of high Li concentrations. As an alternative, we demonstrate how the rapid weathering of soluble, Li-rich minerals such as chlorite under low weathering intensities may resolve this apparent discrepancy between data and theory. We also suggest that observed patterns are consistent with geothermal Li sources under low weathering intensities. This work offers a foundation guiding future studies in testing potential mechanisms underlying global riverine δ7Lidiss.
{"title":"Weathering intensity and lithium isotopes: A reactive transport perspective","authors":"M. Winnick, J. Druhan, K. Maher","doi":"10.2475/05.2022.01","DOIUrl":"https://doi.org/10.2475/05.2022.01","url":null,"abstract":"Lithium isotopes have emerged as a powerful tool to probe the response of global weathering to changes in climate. Due to the preferential incorporation of 6Li into clay minerals during chemical weathering, the isotope ratio δ7Li may be used to interrogate the balance of primary mineral dissolution and clay precipitation. This balance has been linked to relative rates of chemical and physical denudation, such that dissolved δ7Li (δ7Lidiss) is highest at moderate weathering intensities when chemical and physical denudation are comparable. However, we argue that current theory linking δ7Li to weathering regimes through fluid travel times are unable to explain observations of low δ7Li and high Li concentrations in rapidly eroding settings. In this study, we re-examine the relationships between δ7Li, Li concentration, and weathering regime by incorporating Li isotopes into simulations of weathering profiles using a reactive transport model (CrunchFlow) that includes advective fluxes of regolith to simulate variable erosion rates in response to uplift. In these simulations, fractionation is implemented through a kinetic fractionation factor during clay precipitation, which allows the δ7Li of dissolved and suspended loads in the model to vary as a function of Li/Al ratios in primary and secondary minerals. When the model is run over a range of infiltration and erosion rates, simulations reproduce observed global patterns of δ7Lidiss and suspended load δ7Li as a function of weathering intensity, controlled primarily by water travel times and mineral residence times in weathered bedrock. We find that reduced water travel times at low weathering intensity, however, are inconsistent with observations of high Li concentrations. As an alternative, we demonstrate how the rapid weathering of soluble, Li-rich minerals such as chlorite under low weathering intensities may resolve this apparent discrepancy between data and theory. We also suggest that observed patterns are consistent with geothermal Li sources under low weathering intensities. This work offers a foundation guiding future studies in testing potential mechanisms underlying global riverine δ7Lidiss.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44313854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chao Wang, D. Evans, Meng Li, Ji-Heng Zhang, Jian Han, Bin Wen, J. Wang, Junming Zhao
Unraveling the timing, location, and mechanisms of cratonic aggregation in Earth's continental jigsaw puzzle is a key factor for plate tectonic reconstructions. The Quanji Block (QB) is a sliver of anomalously old and well-preserved continental crust embedded within the Paleozoic-Mesozoic tectonic collage of the northeastern Tibetan Plateau and has played a critical role in Proto-/Paleotethys paleogeographic reconstructions. New geological mapping, stratigraphic logging, and geochronological analysis lead to a refined understanding of QB's history from Paleoproterozoic to present. Deposited atop a largely Paleoproterozoic basement, the Quanji Group records rifting and epicratonic cover at 1.7 to 1.6 Ga. The Quanji Group is unconformably overlain by the Xiaogaolu Group, which preserves black shale, Ediacaran-type Charnia, ribbon-shaped fossils and a late Ediacaran glaciation. U-Pb detrital zircon ages from Cambrian Olongbuluke Group marine platform deposits are quite different from ages in underlying units, with a minor component of Neoproterozoic (880–815 Ma) ages. The apparent change in detrital zircon sources coincides with a regionally expressed Great Unconformity during the Precambrian–Cambrian transition. The new stratigraphy and U-Pb geochronology of QB suggest that the late Paleoproterozoic to Cambrian history of QB has a remarkable similarity to that of the southern margin of North China Block (NCB), indicating that the QB has been displaced dextrally from an initial location adjacent to NCB. The transform motion occurred in stages between ca. 350 and 200 Ma, which suggests that transform tectonism appears to be an essential element of any viable model for kinematic development of the Paleo-Tethyan oceanic domains and the ultimate cratonic assembly of eastern Asia.
{"title":"Proterozoic-Mesozoic development of the Quanji block from northern Tibet and the cratonic assembly of eastern Asia","authors":"Chao Wang, D. Evans, Meng Li, Ji-Heng Zhang, Jian Han, Bin Wen, J. Wang, Junming Zhao","doi":"10.2475/05.2022.03","DOIUrl":"https://doi.org/10.2475/05.2022.03","url":null,"abstract":"Unraveling the timing, location, and mechanisms of cratonic aggregation in Earth's continental jigsaw puzzle is a key factor for plate tectonic reconstructions. The Quanji Block (QB) is a sliver of anomalously old and well-preserved continental crust embedded within the Paleozoic-Mesozoic tectonic collage of the northeastern Tibetan Plateau and has played a critical role in Proto-/Paleotethys paleogeographic reconstructions. New geological mapping, stratigraphic logging, and geochronological analysis lead to a refined understanding of QB's history from Paleoproterozoic to present. Deposited atop a largely Paleoproterozoic basement, the Quanji Group records rifting and epicratonic cover at 1.7 to 1.6 Ga. The Quanji Group is unconformably overlain by the Xiaogaolu Group, which preserves black shale, Ediacaran-type Charnia, ribbon-shaped fossils and a late Ediacaran glaciation. U-Pb detrital zircon ages from Cambrian Olongbuluke Group marine platform deposits are quite different from ages in underlying units, with a minor component of Neoproterozoic (880–815 Ma) ages. The apparent change in detrital zircon sources coincides with a regionally expressed Great Unconformity during the Precambrian–Cambrian transition. The new stratigraphy and U-Pb geochronology of QB suggest that the late Paleoproterozoic to Cambrian history of QB has a remarkable similarity to that of the southern margin of North China Block (NCB), indicating that the QB has been displaced dextrally from an initial location adjacent to NCB. The transform motion occurred in stages between ca. 350 and 200 Ma, which suggests that transform tectonism appears to be an essential element of any viable model for kinematic development of the Paleo-Tethyan oceanic domains and the ultimate cratonic assembly of eastern Asia.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49037081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The New Idria serpentinite body in the Coast Ranges of California is a diapir that resulted from the interaction of the migrating Mendocino trench-ridge-transform fault triple junction, transpression, metasomatic fluids, and previously subducted oceanic crust and mantle. Northward propagation of the San Andreas fault progressively eliminated the original subduction zone, allowing seawater to penetrate into the formerly subducting abyssal peridotite mantle, triggering serpentinization. The associated physical changes in density, volume, and strength yielded an expanding, buoyantly rising serpentinite protrusion, facilitated by transpression along the San Andreas fault. Sedimentary facies and intrusion of minor cross cutting syenite and alkali basalt dikes indicate that the serpentinization-driven diapir buoyantly rose and widely breached the surface by ca. 14 Ma, attending migration of the Mendocino Triple Junction past the latitude of New Idria.
{"title":"New Idria serpentinite protrusion, Diablo Range, California: From upper mantle to the surface","authors":"R. Coleman, J. Gooley, R. Gregory, S. Graham","doi":"10.2475/04.2022.01","DOIUrl":"https://doi.org/10.2475/04.2022.01","url":null,"abstract":"The New Idria serpentinite body in the Coast Ranges of California is a diapir that resulted from the interaction of the migrating Mendocino trench-ridge-transform fault triple junction, transpression, metasomatic fluids, and previously subducted oceanic crust and mantle. Northward propagation of the San Andreas fault progressively eliminated the original subduction zone, allowing seawater to penetrate into the formerly subducting abyssal peridotite mantle, triggering serpentinization. The associated physical changes in density, volume, and strength yielded an expanding, buoyantly rising serpentinite protrusion, facilitated by transpression along the San Andreas fault. Sedimentary facies and intrusion of minor cross cutting syenite and alkali basalt dikes indicate that the serpentinization-driven diapir buoyantly rose and widely breached the surface by ca. 14 Ma, attending migration of the Mendocino Triple Junction past the latitude of New Idria.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43198975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Mohammadi, J. Ruh, M. Guillong, O. Laurent, L. Aghajari
The Kopet Dagh mountains in NE Iran exhibit a 7-km-thick continuous sedimentary sequence recording detritus from exposed surrounding terranes from the last 175 Ma. This work presents a multi-disciplinary geochronologic and provenance analysis in an attempt to identify and date major geologic events along the northern segment of the Tethys and reconstruct the regional tectonic history from Gondwana-related rifting until the Alpine orogeny. Sandstone framework, heavy mineral analysis, U-Pb dating of detrital zircons, and Hf-isotope ratio measurements on dated zircons from Triassic to Paleocene sandstones indicate three main tectonic events that include Early Silurian intracontinental rifting (opening of Paleo-Tethys), Early Carboniferous rifting of a back-arc basin (Aghdarband Complex), and Late Triassic collisional to post-collisional magmatism (Paleo-Tethys collision). Mineralogical and age peak considerations indicate that detritus was supplied from the south into the extensional Kopet Dagh Basin during Middle Jurassic, while Cretaceous to Paleocene sandstones show signs of increasing recycling.
{"title":"From Gondwana rifting to Alpine orogeny: Detrital zircon geochronologic and provenance signals from the Kopet Dagh Basin (NE Iran)","authors":"A. Mohammadi, J. Ruh, M. Guillong, O. Laurent, L. Aghajari","doi":"10.2475/04.2022.02","DOIUrl":"https://doi.org/10.2475/04.2022.02","url":null,"abstract":"The Kopet Dagh mountains in NE Iran exhibit a 7-km-thick continuous sedimentary sequence recording detritus from exposed surrounding terranes from the last 175 Ma. This work presents a multi-disciplinary geochronologic and provenance analysis in an attempt to identify and date major geologic events along the northern segment of the Tethys and reconstruct the regional tectonic history from Gondwana-related rifting until the Alpine orogeny. Sandstone framework, heavy mineral analysis, U-Pb dating of detrital zircons, and Hf-isotope ratio measurements on dated zircons from Triassic to Paleocene sandstones indicate three main tectonic events that include Early Silurian intracontinental rifting (opening of Paleo-Tethys), Early Carboniferous rifting of a back-arc basin (Aghdarband Complex), and Late Triassic collisional to post-collisional magmatism (Paleo-Tethys collision). Mineralogical and age peak considerations indicate that detritus was supplied from the south into the extensional Kopet Dagh Basin during Middle Jurassic, while Cretaceous to Paleocene sandstones show signs of increasing recycling.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43277084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Planavsky, M. Fakhraee, E. Bolton, C. Reinhard, T. Isson, Shuang Zhang, Benjamin J. W. Mills
The carbonate carbon isotope record has been traditionally interpreted as evidence of stability in the globally integrated ratio of organic to total carbon burial from Earth's surface environments over the past ∼3.8 billion years, but recent work has begun to question this conclusion. Herein, we use a reactive-transport modeling approach to track organic carbon oxidation at varying atmospheric oxygen levels and use that information to provide a rough estimate of net primary production through time. Our results support the emerging view that there was extensive variability in the fraction of carbon buried as organic matter (fb,org) throughout Earth's history. We strengthen the case that the carbonate carbon isotope record has been characterized by a relatively constant baseline value over time due to a fundamental mechanistic link between atmospheric O2 levels and the carbon isotope composition of net inputs to the ocean-atmosphere system. Further, using estimates of the organic carbon burial flux (Fb,org) and the burial efficiency of the carbon pump from our marine reactive-transport modeling, we also support previous work suggesting extensive fluctuation in marine net primary production over time.
{"title":"On carbon burial and net primary production through Earth's history","authors":"N. Planavsky, M. Fakhraee, E. Bolton, C. Reinhard, T. Isson, Shuang Zhang, Benjamin J. W. Mills","doi":"10.2475/03.2022.01","DOIUrl":"https://doi.org/10.2475/03.2022.01","url":null,"abstract":"The carbonate carbon isotope record has been traditionally interpreted as evidence of stability in the globally integrated ratio of organic to total carbon burial from Earth's surface environments over the past ∼3.8 billion years, but recent work has begun to question this conclusion. Herein, we use a reactive-transport modeling approach to track organic carbon oxidation at varying atmospheric oxygen levels and use that information to provide a rough estimate of net primary production through time. Our results support the emerging view that there was extensive variability in the fraction of carbon buried as organic matter (fb,org) throughout Earth's history. We strengthen the case that the carbonate carbon isotope record has been characterized by a relatively constant baseline value over time due to a fundamental mechanistic link between atmospheric O2 levels and the carbon isotope composition of net inputs to the ocean-atmosphere system. Further, using estimates of the organic carbon burial flux (Fb,org) and the burial efficiency of the carbon pump from our marine reactive-transport modeling, we also support previous work suggesting extensive fluctuation in marine net primary production over time.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43446224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Wamsutta and Nineteenmile Brook Diorites, two small plutons located in the White Mountains of New Hampshire, have bearing on the tectonic setting of magmatism between 410 and 407 Ma in this portion of the northern Appalachians. The unmetamorphosed, undated Nineteenmile Brook pluton has arc basalt affinities, produced in the same arc as the mafic magmas that were mingled with the ∼410 Ma Meredeth Porphyric Granite of central New Hampshire. These volcanic arc magmas from a westerly dipping subduction zone contributed both heat and mass to the petrogenesis of the New Hampshire Plutonic Suite (NHPS), producing the high temperature melts of the Kinsman Granodiorite of the NHPS. These peraluminous NHPS magmas were emplaced during collision of Avalonia with Laurentia, forming the bases of Acadian thrust sheets. The ∼408 Ma Wamsutta Diorite has appinite-like textures and chemically is a low SiO2 adakite, with Sr/Y ratios of ∼ 400 and (La/Yb)N between 80 and 130. These magmas were generated after flat slab, subduction erosion mixed basaltic rocks into the mantle wedge and partially melted the mafic rocks in the garnet stability field. The melts interacted with the surrounding peridotite to attain the low SiO2 adakite characteristics. At this same time, the ∼407 Ma Exeter Diorite and other arc plutons were emplaced in the Merrimack belt of southeastern New Hampshire. By 400 Ma, continued westerly dipping subduction provided mafic magma underplating to partially melt lower crustal amphibolites, generating the Spaulding Tonalite. Subsequently, lower crustal delamination and asthenospheric upwelling provided the heat source that produced a younger, post-tectonic suite of magmas between 390 and 370 Ma that, while having arc signatures because of the heritage of their crustal source rocks, are not arc magmas because subduction is thought to have ceased by this time. These plutons include the mafic rocks of the Northeast Kingdom of Vermont and the Mooselookmeguntic Igneous Complex of NH and ME. This same heat source may have contributed to melting lower to midcrustal metasediments to produce the widespread peraluminous Concord Granite of Vermont, New Hampshire, and western Maine.
Wamsutta和19mile Brook闪长岩是位于新罕布什尔州白山的两个小型深成岩体，与阿巴拉契亚山脉北部这一地区410至407 Ma之间的岩浆活动的构造背景有关。未变质、未注明日期的十九英里溪深成岩体具有弧玄武岩亲和力，与新罕布什尔州中部约410 Ma Meredeth斑岩花岗岩混合的镁铁质岩浆在同一弧中产生。这些来自向西倾斜俯冲带的火山弧岩浆为新罕布什尔Plutonic Suite（NHPS）的岩石成因提供了热量和质量，产生了NHPS的Kinsman Granodiorite的高温熔体。这些超发光的NHPS岩浆是在阿瓦隆尼亚与劳伦蒂亚碰撞期间侵位的，形成了阿卡迪亚逆冲片的基底。～408 Ma Wamsutta闪长岩具有类似阿斑岩的结构，化学性质为低SiO2埃达克岩，Sr/Y比为～400，（La/Yb）N在80至130之间。这些岩浆是在平板、俯冲侵蚀将玄武岩混合到地幔楔中并使石榴石稳定区的镁铁质岩石部分熔融后产生的。熔体与周围的橄榄岩相互作用，以获得低SiO2埃达克岩特征。与此同时，约407 Ma Exeter闪长岩和其他弧形深成岩体被侵位在新罕布什尔州东南部的梅里马克带。到400 Ma，持续的西向俯冲提供了镁铁质岩浆底侵作用，使下地壳角闪岩部分熔融，生成斯波丁方钠石。随后，下地壳分层和软流圈上升流提供了热源，在390至370 Ma之间产生了一套更年轻的后构造岩浆，这些岩浆虽然由于其地壳源岩的继承而具有弧形特征，但不是弧形岩浆，因为俯冲被认为在此时已经停止。这些深成岩体包括佛蒙特州东北王国的镁铁质岩石以及NH和ME的Mooselookmeguntic火成岩杂岩。同样的热源可能有助于融化地壳下部至中部的变质沉积物，从而产生佛蒙特州、新罕布什尔州和缅因州西部广泛分布的过铝质康科德花岗岩。
{"title":"The petrogenesis and tectonic setting of the New Hampshire Plutonic Suite: Towards a more comprehensive model for the magmatism of the Acadian Orogeny","authors":"M. Dorais","doi":"10.2475/03.2022.03","DOIUrl":"https://doi.org/10.2475/03.2022.03","url":null,"abstract":"The Wamsutta and Nineteenmile Brook Diorites, two small plutons located in the White Mountains of New Hampshire, have bearing on the tectonic setting of magmatism between 410 and 407 Ma in this portion of the northern Appalachians. The unmetamorphosed, undated Nineteenmile Brook pluton has arc basalt affinities, produced in the same arc as the mafic magmas that were mingled with the ∼410 Ma Meredeth Porphyric Granite of central New Hampshire. These volcanic arc magmas from a westerly dipping subduction zone contributed both heat and mass to the petrogenesis of the New Hampshire Plutonic Suite (NHPS), producing the high temperature melts of the Kinsman Granodiorite of the NHPS. These peraluminous NHPS magmas were emplaced during collision of Avalonia with Laurentia, forming the bases of Acadian thrust sheets. The ∼408 Ma Wamsutta Diorite has appinite-like textures and chemically is a low SiO2 adakite, with Sr/Y ratios of ∼ 400 and (La/Yb)N between 80 and 130. These magmas were generated after flat slab, subduction erosion mixed basaltic rocks into the mantle wedge and partially melted the mafic rocks in the garnet stability field. The melts interacted with the surrounding peridotite to attain the low SiO2 adakite characteristics. At this same time, the ∼407 Ma Exeter Diorite and other arc plutons were emplaced in the Merrimack belt of southeastern New Hampshire. By 400 Ma, continued westerly dipping subduction provided mafic magma underplating to partially melt lower crustal amphibolites, generating the Spaulding Tonalite. Subsequently, lower crustal delamination and asthenospheric upwelling provided the heat source that produced a younger, post-tectonic suite of magmas between 390 and 370 Ma that, while having arc signatures because of the heritage of their crustal source rocks, are not arc magmas because subduction is thought to have ceased by this time. These plutons include the mafic rocks of the Northeast Kingdom of Vermont and the Mooselookmeguntic Igneous Complex of NH and ME. This same heat source may have contributed to melting lower to midcrustal metasediments to produce the widespread peraluminous Concord Granite of Vermont, New Hampshire, and western Maine.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44798434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Maffre, Y. Goddéris, A. Pohl, Y. Donnadieu, S. Carretier, Guillaume Le Hir
The first forests appeared on the continents during the Givetian stage of the Devonian. The fossil record shows that, by the end of the Devonian, vascular plants and forests were common and widespread in the wet lowlands. Although the impact of this major event on chemical weathering of the continents is reasonably known, the coeval change in physical erosion has never been explored. Here, we build a mathematical description of the coupled response of the physical erosion and chemical weathering on the continents, to the colonization by vascular plants over the course of the Devonian. This spatially-resolved erosion model is coupled to the GEOCLIM model to simulate the response of the global carbon and alkalinity cycles, and of climate, to the colonization phase. A set of simulations is described, assuming an increased weatherability of the continental surface, and a change in physical erosion which can be either a decrease or an increase in response to the spreading of vascular plants. We explore first the initial pre-colonization and the final post-colonization steady states of the surficial Earth system. Then, we simulate the transient states of the Earth system in response to theoretical randomized scenarios for the colonization. We find that the pathways of the colonization have a major impact on the CO2 history through the Devonian. Depending on the magnitude of the change in physical erodibility and chemical weatherability, and on the colonization scenario, atmospheric CO2 evolution may display contrasting behaviors: from a uniform CO2 decrease over the Devonian, to more complex patterns characterized first by a global warming from the end of the Givetian into the Frasnian, and then by a final cooling, in first order agreement with the proxy data for CO2 and reconstructed climate evolution.
{"title":"The complex response of continental silicate rock weathering to the colonization of the continents by vascular plants in the Devonian","authors":"P. Maffre, Y. Goddéris, A. Pohl, Y. Donnadieu, S. Carretier, Guillaume Le Hir","doi":"10.2475/03.2022.02","DOIUrl":"https://doi.org/10.2475/03.2022.02","url":null,"abstract":"The first forests appeared on the continents during the Givetian stage of the Devonian. The fossil record shows that, by the end of the Devonian, vascular plants and forests were common and widespread in the wet lowlands. Although the impact of this major event on chemical weathering of the continents is reasonably known, the coeval change in physical erosion has never been explored. Here, we build a mathematical description of the coupled response of the physical erosion and chemical weathering on the continents, to the colonization by vascular plants over the course of the Devonian. This spatially-resolved erosion model is coupled to the GEOCLIM model to simulate the response of the global carbon and alkalinity cycles, and of climate, to the colonization phase. A set of simulations is described, assuming an increased weatherability of the continental surface, and a change in physical erosion which can be either a decrease or an increase in response to the spreading of vascular plants. We explore first the initial pre-colonization and the final post-colonization steady states of the surficial Earth system. Then, we simulate the transient states of the Earth system in response to theoretical randomized scenarios for the colonization. We find that the pathways of the colonization have a major impact on the CO2 history through the Devonian. Depending on the magnitude of the change in physical erodibility and chemical weatherability, and on the colonization scenario, atmospheric CO2 evolution may display contrasting behaviors: from a uniform CO2 decrease over the Devonian, to more complex patterns characterized first by a global warming from the end of the Givetian into the Frasnian, and then by a final cooling, in first order agreement with the proxy data for CO2 and reconstructed climate evolution.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47564169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Kukla, J. Rugenstein, E. Driscoll, D. Ibarra, C. Chamberlain
In the last two decades, analytical advances and a growing interest in relevant research questions has brought a rapid increase in the amount of stable isotope data used for reconstructing terrestrial paleoclimates and environments. As the spatial and temporal resolution of proxy data continues to improve, the quantitative interpretation of these data is becoming increasingly common. These advances in data resolution and theory bring opportunities for multi-proxy comparisons, synthesis and modeling of large datasets, integration with paleoecological datasets, improved climate model benchmarking, and more. Here, in an effort to support these growing avenues of research, we present The PATCH Lab (Paleo-Analysis of Terrestrial Climate and Hydrology)—an online portal to discover, download, and quantitatively analyze deep time (>1 Ma) terrestrial stable isotope data. The PATCH Lab portal hosts a new database that currently includes 27009 stable isotope measurements from 211 publications spanning multiple terrestrial proxies, and quantitative models for interpreting water isotope and soil carbonate data. Data query, download, and modeling results are organized into user-friendly graphical interfaces that export datasets as .csv files. New data can be easily submitted to the PATCH Lab curators through the portal by completing a data submission template. The PATCH Lab, with the help of community engagement, serves as a resource for archiving terrestrial stable isotope data, building paleo “isoscapes”, and increasing accessibility to quantitative methods of investigating terrestrial stable isotopes in paleoclimate.
{"title":"The PATCH Lab v1.0: A database and workspace for Cenozoic terrestrial paleoclimate and environment reconstruction","authors":"T. Kukla, J. Rugenstein, E. Driscoll, D. Ibarra, C. Chamberlain","doi":"10.31223/x5pk9w","DOIUrl":"https://doi.org/10.31223/x5pk9w","url":null,"abstract":"In the last two decades, analytical advances and a growing interest in relevant research questions has brought a rapid increase in the amount of stable isotope data used for reconstructing terrestrial paleoclimates and environments. As the spatial and temporal resolution of proxy data continues to improve, the quantitative interpretation of these data is becoming increasingly common. These advances in data resolution and theory bring opportunities for multi-proxy comparisons, synthesis and modeling of large datasets, integration with paleoecological datasets, improved climate model benchmarking, and more. Here, in an effort to support these growing avenues of research, we present The PATCH Lab (Paleo-Analysis of Terrestrial Climate and Hydrology)—an online portal to discover, download, and quantitatively analyze deep time (>1 Ma) terrestrial stable isotope data. The PATCH Lab portal hosts a new database that currently includes 27009 stable isotope measurements from 211 publications spanning multiple terrestrial proxies, and quantitative models for interpreting water isotope and soil carbonate data. Data query, download, and modeling results are organized into user-friendly graphical interfaces that export datasets as .csv files. New data can be easily submitted to the PATCH Lab curators through the portal by completing a data submission template. The PATCH Lab, with the help of community engagement, serves as a resource for archiving terrestrial stable isotope data, building paleo “isoscapes”, and increasing accessibility to quantitative methods of investigating terrestrial stable isotopes in paleoclimate.","PeriodicalId":7660,"journal":{"name":"American Journal of Science","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2022-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46613815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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