Journal of Geodynamics最新文献

Tectonic reevaluation of West Cameroon domain: Insights from high-resolution gravity models and advanced edge detection methods 重新评估喀麦隆西部地区的构造：高分辨率重力模型和先进边缘探测方法的启示

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-10-18 DOI: 10.1016/j.jog.2024.102061

Zambou Tsopgni Yasmine , Franck Eitel Kemgang Ghomsi , Robert Nouayou , Luan Thanh Pham , Zakari Aretouyap , Janvier Domra Kana , Ojima Isaac Apeh , Robert Tenzer , Ahmed M. Eldosouky

The West Cameroon region, characterized by a diverse geomorphology of highlands and plains resulting from tectonic processes across different geological ages, has been extensively explored for natural resources. Recognizing the significance of its tectonic and magmatic features associated with seismic and volcanic activity, this study focuses on geodynamic investigations of the Cameroon Volcanic Line (CVL). Despite previous efforts, detailed structural geophysical studies of the West Cameroon domain have proven inconclusive, prompting a comprehensive structural reinterpretation. Utilizing the high-resolution SGG-UGM-2 satellite gravity model and innovative processing techniques, including the horizontal gradient of a modified tilt (HG_STDR), the balanced horizontal gradient (BHG), the tilt of the horizontal gradient (TAHG), the improvised horizontal gradient tilt angle (impTAHG), and the Tilt Depth method, our research aims to enhance the interpretational quality of tectonic lineaments. By separating regional and residual anomalies in the Bouguer gravity map and applying a combination of filters to delineate geological units, the BHG filter emerges as a robust tool that highlights subsurface edges without generating false features. This approach unveils previously undetected NNW-SSE-oriented lineaments, confirming the presence of deep fractures and faults in Bafoussam, Nkongsamba, and along the Benue Trough, corroborated by newly discovered NNW-SSW trending lineaments. The study suggests that the region’s topography is overcompensated by deep mountain roots and compressive tectonism. Digitizing the BHG filter produces a structural map, revealing predominant NE trends in identified geological margins, including NNE-SSW, N-S, NW-SE, E-W, and NE-SW directions. Geological contacts between granite and high-grade gneiss are indicated by NNW-SSE and NNE-SSW trending lineaments along the Benue Trough. These results contribute significantly to the understanding of the tectonic setting of the West Cameroon Domain.

西喀麦隆地区的特点是不同地质年代的构造过程造成的高地和平原的多样化地貌，该地区的自然资源已被广泛勘探。认识到与地震和火山活动相关的构造和岩浆特征的重要性，本研究侧重于喀麦隆火山线（CVL）的地球动力学调查。尽管之前做了大量工作，但对西喀麦隆地区进行的详细构造地球物理研究仍未得出结论，因此需要对该地区进行全面的构造重新解释。利用高分辨率 SGG-UGM-2 卫星重力模型和创新的处理技术，包括修正倾斜的水平梯度（HGSTDR）、平衡水平梯度（BHG）、水平梯度倾斜（TAHG）、简易水平梯度倾斜角（impTAHG）和倾斜深度法，我们的研究旨在提高构造线形的解释质量。通过分离布格尔重力图中的区域异常和残余异常，并应用滤波器组合来划分地质单元，BHG 滤波器成为一种强大的工具，它能突出地下边缘，而不会产生错误特征。这种方法揭示了以前未发现的 NNW-SSE 走向线型，证实了巴富萨姆、恩孔桑巴和贝努埃海槽沿线存在深层断裂和断层，新发现的 NNW-SSW 走向线型也证实了这一点。研究表明，该地区的地形被深山根系和压缩构造所过度补偿。通过对 BHG 滤波进行数字化处理，绘制了一张构造图，揭示了已确定地质边缘的主要东北走向，包括 NNE-SSW、N-S、NW-SE、E-W 和 NE-SW 走向。贝努埃海槽沿线的 NNW-SSE 和 NNE-SSW 走向线状显示了花岗岩和高品位片麻岩之间的地质接触。这些结果极大地促进了人们对西喀麦隆域构造背景的了解。

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引用次数: 0

Alternative thermal histories of Earth-like planets: Influence of key parameters 类地行星的另一种热历史：关键参数的影响

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-10-18 DOI: 10.1016/j.jog.2024.102062

Edgardo Cañón-Tapia

The thermal evolution of any planet can be influenced by many factors: the initial temperature profile, the distribution of specific materials within the planet, the existence or lack of a gaseous atmosphere, the effects of early and “late” collision events. Insights concerning the influence of those factors can be obtained by examining solutions to the heat equation, applied to spherical bodies. General trends identified in this work include: 1) Moderate conductive materials contribute to efficiently flatten the temperature gradients, whereas insulating materials promote the preservation of steep temperature gradients. 2) It is not necessary to invoke convection to achieve a relatively flat temperature gradient; moderately conductive materials might achieve the same result without any advective motion involved. 3) Heat transport can take place both outwards and inwards, depending on the initial distribution of temperatures. 4) If the initial temperatures near the center of a planet are low, they will tend to remain low even if heat production takes place at its middle or upper parts. 5) Gradients of temperature near the surface of a planet may not reflect temperature variations at its middle or central parts. 6) Changes of phase exert a strong influence on the evolution of temperature profiles within a planet. 7) Highly insulating atmospheric layers can be important in determining the time of solidification of the upper layer of a magma ocean but not all atmospheres are equally efficient in that respect. As a result, models that give for granted the existence of deep mantle convection on Earth are justified only in the context of models of planet formation that require high initial temperatures; the standard model of a cold solar nebula is not consistent with such deep mantle convective movements.

任何行星的热演化都会受到许多因素的影响：初始温度曲线、行星内部特定物质的分布、是否存在气态大气、早期和 "晚期 "碰撞事件的影响。通过研究适用于球体的热方程的解，可以深入了解这些因素的影响。这项研究发现的总体趋势包括1) 适度导电材料有助于有效地平缓温度梯度，而绝缘材料则有助于保持陡峭的温度梯度。2) 实现相对平缓的温度梯度不一定需要对流；适度导电的材料可以在不涉及任何平流运动的情况下实现相同的结果。3) 热量既可以向外也可以向内传播，这取决于初始温度分布。4) 如果行星中心附近的初始温度较低，即使热量产生于中部或上部，温度也会保持在较低水平。5) 行星表面附近的温度梯度可能无法反映其中部或中央部分的温度变化。6) 相位变化对行星内部温度曲线的演变有很大影响。7) 高绝缘大气层对决定岩浆洋上层的凝固时间非常重要，但并非所有大气层在这方面都同样有效。因此，只有在需要较高初始温度的行星形成模型中，才有理由认为地球上存在理所当然的深地幔对流；冷太阳星云的标准模型与这种深地幔对流运动并不一致。

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引用次数: 0

Unveiling crustal deformation patterns along the north Tabriz fault from 2015 to 2022 using multi-temporal InSAR analysis 利用多时InSAR分析揭示2015年至2022年北大不里士断层沿线的地壳变形模式

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-10-18 DOI: 10.1016/j.jog.2024.102060

Zahra Alizadeh Zakaria , Farshid Farnood Ahmadi , Hamid Ebadi

This paper presents a comprehensive study on the recognition of crustal deformation patterns surrounding the North Tabriz Fault in Northwestern Iran, utilizing Multi-Temporal InSAR analysis. The fault, despite its seismic inactivity for over two centuries, has a long history of ancient seismicity, with earthquake recurrence intervals exceeding two centuries. This makes it highly susceptible to future activity and the generation of significant and devastating earthquakes. However, limited research has been conducted on extracting and modeling deformation patterns of the North Tabriz Fault to identify its active segments. The primary objective of this study is to derive a general trend for fault displacement and investigate regions under pressure in terms of abnormal crustal movements. The results indicate that the Earth's crust in the surrounding regions of the central and northwest segments of the fault exhibits an upward movement ranging from approximately 2 to 10 millimeters per year from 2015 to 2022. In contrast, neighboring areas of the northwestern fault, as well as the northwestern, western, and southwestern parts of Tabriz County, experience ground subsidence with rates ranging from approximately 5 to 40 millimeters per year. These findings are consistent with GNSS-derived line-of-sight measurements obtained from some IPGN stations around the fault with an RMSE of 1.72 mm/yr. Furthermore, the study identifies critical points near the fault that exhibit varying and diverse displacement patterns over time, suggesting significant strain and notable stress within the subsurface environment. According to the analysis of time series data on crustal movements at the identified critical points, it has been found that the prevailing motion pattern of the Earth's crust within the fault zone largely conforms to a sinusoidal descending pattern. Additionally, recent earthquakes in the northwest vicinity of the fault have been observed to occur close to these critical points. Using line-of-sight (LOS) data acquired at these critical points, the study estimates a slip rate of 7.71 ± 0.01 mm/year and a locking depth of 11.27 ± 0.01 km, contributing to a better understanding of the fault's seismogenic behavior. These findings provide valuable insights into the crustal deformation patterns around the North Tabriz Fault, highlighting active segments and regions under pressure.

本文介绍了利用多时相 InSAR 分析识别伊朗西北部北大不里士断层周围地壳变形模式的综合研究。尽管该断层已有两个多世纪没有发生地震，但其古代地震活动历史悠久，地震重现间隔超过两个世纪。这使其极易在未来发生活动，并产生重大破坏性地震。然而，对北大不里士断层的变形模式进行提取和建模以确定其活跃区段的研究十分有限。本研究的主要目的是得出断层位移的总体趋势，并调查地壳异常运动的压力区域。研究结果表明，从 2015 年到 2022 年，断层中部和西北部周边地区的地壳每年向上移动约 2 至 10 毫米。相比之下，西北断层邻近地区以及大不里士县西北部、西部和西南部地区的地面沉降速率约为每年 5 至 40 毫米。这些发现与从断层周围一些 IPGN 站获得的全球导航卫星系统视线测量结果一致，其 RMSE 为 1.72 毫米/年。此外，研究还确定了断层附近的临界点，这些临界点随着时间的推移呈现出不同的位移模式，表明地下环境中存在巨大的应变和显著的应力。根据对已确定临界点地壳运动时间序列数据的分析，发现断层带内地壳的主要运动模式基本符合正弦下降模式。此外，据观测，最近在断层西北部附近发生的地震就发生在这些临界点附近。该研究利用在这些临界点获取的视线（LOS）数据，估算出滑动速率为 7.71 ± 0.01 毫米/年，锁定深度为 11.27 ± 0.01 千米，从而有助于更好地了解该断层的致震行为。这些发现为了解北大不里士断层周围的地壳变形模式提供了宝贵的见解，突出了活跃地段和受压区域。

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引用次数: 0

Insights into the crustal and the magmatic feeding structure at the Payunia Volcanic Province highlighted by geophysical methods, in the retroarc of the Southern Central Andes 通过地球物理方法深入了解安第斯山脉中南部弧后地区帕尤尼亚火山省的地壳和岩浆哺育结构

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-09-19 DOI: 10.1016/j.jog.2024.102059

Silvina Nacif , Martin Schimmel , Andrés Nacif , Laura Godoy , Marianela Lupari , Renzo Furlani , Mario Gimenez , Andrés Folguera

The Payunia Volcanic Province is a Quaternary volcanic plateau emplaced in the retroarc area in the northern Neuquén Mesozoic Basin, associated with a hydrocarbon system. At deeper levels, this basin is linked to different intrusive systems that developed in the retroarc region at different times, during the Jurassic, Cretaceous, Eocene, Miocene, and even the Quaternary which influenced the hydrocarbon system maturity. We analyzed the Moho structure through this retroarc region, as well as the crustal structure affected by different stages of regional extension. From continuous seismic noise data, we calculated the autocorrelograms to obtain the reflection response below each seismological station. This allowed imaging the surface of primary crustal reflectors and in a few stations the top of an asthenospheric anomaly (SWAP) found by magnetotelluric survey and in concordance with satellite magnetic data. The crustal reflectors were identified in all stations at a mean two-way travel time of about ∼8.5 s and ∼12.5 s using frequency bands of about 1.0–2.4 Hz. Therefore, this is the first geophysical research that estimates the depth of the magmatic system, hosted at the top of the lower crust and the Moho discontinuity. The deepest reflector, only recognized in 4 stations, was observed with a two-way travel time of 17.2 s to 19.6 s. We used a mean one-dimensional Vp model to obtain the corresponding reflector depths which constrain the two-dimensional forward gravity model that fits with the observed regional anomaly for the region. We finally established a relationship between the shallowest sublithospheric electrical conductivity anomalies determined in previous researches and the strong deep reflections observed in some of the seismological stations. This information may help to constrain geochemical and petrological models and re-evaluate the hydrocarbon system maturity of the northern Neuquén basin.

帕尤尼亚火山省是一个第四纪火山高原，位于内乌肯中生代盆地北部的弧后地区，与一个油气系统有关。在更深的层次上，该盆地与弧后地区在不同时期（侏罗纪、白垩纪、始新世、中新世，甚至第四纪）形成的不同侵入系统有关，这些侵入系统影响了油气系统的成熟度。我们分析了贯穿弧后地区的莫霍结构，以及受区域延伸不同阶段影响的地壳结构。根据连续地震噪声数据，我们计算了自相关图，以获得每个地震台站下方的反射响应。这使得我们能够对主要地壳反射体的表面进行成像，并在少数几个台站中对磁电勘测发现的、与卫星磁数据一致的岩石圈异常（SWAP）的顶部进行成像。所有站点的地壳反射体都是在平均双向移动时间约为∼8.5 秒和∼12.5 秒的情况下使用约 1.0-2.4 赫兹的频带确定的。因此，这是首次估算岩浆系统深度的地球物理研究，岩浆系统位于下地壳顶部和莫霍不连续处。最深的反射体仅在 4 个站点被观测到，其双向移动时间为 17.2 秒至 19.6 秒。我们利用平均一维 Vp 模型获得了相应的反射体深度，从而约束了二维前向重力模型，该模型与观测到的该地区区域异常相吻合。我们最终确定了以往研究中确定的岩石圈下最浅电导率异常与一些地震台站观测到的强深层反射之间的关系。这些信息可能有助于制约地球化学和岩石学模型，并重新评估内乌肯盆地北部油气系统的成熟度。

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引用次数: 0

Artificial intelligence for assessing the planets' positions as a precursor to earthquake events 人工智能评估行星位置作为地震事件的前兆

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-09-17 DOI: 10.1016/j.jog.2024.102057

Tarik El Moudden , Mohamed Amnai , Ali Choukri , Youssef Fakhri , Gherabi Noreddine

Questions about interconnection possibilities between planets’ positions and seismic events on the earth have emerged recently in TV channels, social media, etc. In this study, an Artificial Neural Network (ANN) and Random Forest Regression (RFR) are used to predict the number of earthquakes that can occur on Earth, depending on the Earth’s position relative to other planets and solar positions. Our new integration dataset contains 9809 observations and nine features firstly from the global earthquake archive, which is an authoritative layer by Esri, and secondly from the accurate data web portal “theskylive.com.”.

The results obtained from RFR and ANN prove the partial influence of planets positions on sesimic activity on the earth. In other words, quantitatively through the ANN that gets an accuracy of 68.27 %, MAE of 5.36, MSE of 52.78, RMSE of 7.26, R-Squared of 0.65, and also through the RFR that gets an accuracy of 65.06 %, MAE of 5.60, MSE of 58.21, RMSE of 7.63, R-Squared of 0.67, prove the partial influence on one hand. Qualitatively through the curve of the training phase of the ANN, which is a decreasing and convex function, reinforces the aforementioned proof on the other hand. For these reasons, it can be deduced that there is a possible connection between tectonic stress triggers and the positions of the planets in the solar system. Our dataset was uploaded to the github(https://github.com/mouddentarik/Earthquake01.) as well as the code will be publicly available at the github(https://github.com/mouddentarik/PythonCode_Earthquakes-.) to share our results.

最近，电视频道、社交媒体等出现了关于行星位置与地球地震事件之间相互联系的问题。在这项研究中，我们使用人工神经网络（ANN）和随机森林回归（RFR）来预测地球上可能发生的地震次数，这取决于地球相对于其他行星和太阳的位置。我们的新整合数据集包含 9809 个观测数据和九个特征，首先来自 Esri 的权威图层全球地震档案，其次来自精确数据门户网站 "theskylive.com"。RFR 和 ANN 得出的结果证明了行星位置对地球地震活动的部分影响。换句话说，从定量角度看，ANN 的精确度为 68.27%，MAE 为 5.36，MSE 为 52.78，RMSE 为 7.26，R 平方为 0.65；从定性角度看，RFR 的精确度为 65.06%，MAE 为 5.60，MSE 为 58.21，RMSE 为 7.63，R 平方为 0.67。而 ANN 训练阶段的曲线是一个递减的凸函数，这从定性上加强了上述证明。因此，可以推断出构造应力触发器与太阳系中的行星位置之间可能存在联系。我们的数据集已上传到 github(https://github.com/mouddentarik/Earthquake01.)，代码也将在 github(https://github.com/mouddentarik/PythonCode_Earthquakes-.) 公开，以分享我们的成果。

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引用次数: 0

Tectonic evolution of the Circum-Moesian orocline of the Carpatho-Balkanides: Paleomagnetic constraints 喀尔巴阡-巴尔干半岛环莫西米亚岩层的构造演化：古地磁制约因素

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-09-12 DOI: 10.1016/j.jog.2024.102058

Emő Márton , Vesna Cvetkov , Miodrag Banješević , Gábor Imre , Aleksandar Pačevski

The areas of the present study in eastern Serbia, the Danubicum and the Timok Magmatic Complex (TMC, part of the Geticum) are situated between the Vardar Zone and Moesia. The first is Moesia derived and thrust over the Geticum during the latest Cretaceous, the second represents the central segment of the subduction related Apuseni-Banat-Timok-Srednogorie (ABTS) metallogenic belt. The new results, based on 18 geographically distributed sampling points (228 field oriented drill cores) imply large CW vertical axis rotations for the Upper Jurassic (Lower Cretaceous) carbonates of the Danubicum and a moderate one for the Upper Cretaceous igneous and sedimentary rocks from the TMC. These, together with earlier published paleomagnetic data provide kinematic constraints to test the circum-Moesian backarc-convex orocline model. The strike test plot clearly documents that it is a progressive arc. The starting situation at the time of the volcanic activity in the metallic belt (90–70 Ma) must have been a generally E-W oriented S segment, continuing in NNW-SSE oriented ABT segments. The present geometry of the circum-Moesian belt, in the context of Miocene paleomagnetic results from the Vardar Zone and the Apuseni Mts, is interpreted as the result of two main tectonic processes. The first is an about 30° vertical axis CW rotation which took place in coordination with the Vardar Zone (20–17 Ma). The second is an additional 40–65° CW rotation (17–15 Ma) involving also the Danubicum, due to the subduction pull of the E Carpathians in combination with the corner effect of Moesia.

本次研究的地区位于塞尔维亚东部，即位于瓦尔达尔区和莫伊西亚之间的达努比库姆和蒂莫克岩浆岩群（Timok Magmatic Complex，Geticum的一部分）。前者源于莫伊西亚，并在最近的白垩纪期间推移到 Geticum 上，后者代表了与俯冲有关的 Apuseni-Banat-Timok-Srednogorie (ABTS) 成矿带的中心部分。基于 18 个地理分布的取样点（228 个野外定向钻芯）得出的新结果表明，Danubicum 地区上侏罗世（下白垩世）碳酸盐岩的 CW 垂直轴旋转较大，而 TMC 地区上白垩世火成岩和沉积岩的 CW 垂直轴旋转适中。这些数据与早先公布的古地磁数据一起，为测试环马埃岛弧后凸岩圈模型提供了运动学约束。走向测试图清楚地表明这是一个渐进弧。在金属带火山活动时期（90-70 Ma），起始情况肯定是一个总体呈东西走向的 S 段，然后继续呈西北-东南走向的 ABT 段。从瓦尔达尔区和阿普塞尼山的中新世古地磁结果来看，环莫西米亚带目前的几何形状被解释为两个主要构造过程的结果。第一个是与瓦尔达尔区（20-17Ma）协调发生的约 30° 垂直轴 CW 旋转。第二种是由于东喀尔巴阡山脉的俯冲拉力与莫伊西亚的拐角效应相结合，发生了额外的 40-65° CW 旋转（17-15Ma），其中也涉及到多努比库姆山脉。

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引用次数: 0

Special Issue on “Seismic anisotropy – from rock samples to large-scale imprints in the lithosphere-asthenosphere system” 关于 "地震各向异性--从岩石样本到岩石圈-热成层系统的大规模印记 "的特刊

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-09-01 DOI: 10.1016/j.jog.2024.102042

引用次数: 0

Limited sensitivity of Antarctic GIA mass change estimates to lateral viscosity variations 南极 GIA 质量变化估计值对横向粘度变化的敏感性有限

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-08-25 DOI: 10.1016/j.jog.2024.102047

Yoshiya Irie , Jun’ichi Okuno , Koichiro Doi , Takeshige Ishiwa , Yoichi Fukuda

The Gravity Recovery and Climate Experiment (GRACE) has revealed spatiotemporal mass changes in the Antarctic Ice Sheet. However, GRACE data must be corrected for the gravity changes due to glacial isostatic adjustment (GIA). Here we investigate the sensitivity of GIA-induced gravity changes in Antarctica to the lithospheric thickness and upper mantle viscosity using a one-dimensional (1-D) model that assumes a radially varying Earth structure. The sensitivity is assessed using several Antarctic ice-history models that have been widely used to correct GRACE data. The results indicate a trade-off between lithospheric thickness and upper mantle viscosity in evaluating the Antarctic GIA correction. This trade-off exists for all ice-history models; however, the reason for the trade-off differs among models. Furthermore, since there is a sharp contrast in the Earth structure between West and East Antarctica, the adopted ice histories are separated into West and East Antarctic components to examine their contributions to the Antarctic GIA correction. We consider 1-D Earth structures that are averaged from the seismically derived three-dimensional Earth structure for West and East Antarctica. These results indicate that the contributions of the East and West Antarctic loads do not significantly affect the GIA corrections for the West and East Antarctic regions, respectively, and that the trade-off between lithospheric thickness and upper mantle viscosity results in minimal divergence in the assessment of the Antarctic GIA correction between the averaged Earth models of West and East Antarctica. Therefore, the contrast in Earth structure beneath Antarctica may have a limited effect on the ice-mass change estimates for the entire Antarctic Ice Sheet.

重力恢复与气候实验（GRACE）揭示了南极冰盖的时空质量变化。然而，GRACE 数据必须对冰川等静力调整（GIA）引起的重力变化进行校正。在此，我们使用假定地球结构径向变化的一维（1-D）模型，研究了冰川等静力调整引起的南极洲重力变化对岩石圈厚度和上地幔粘度的敏感性。利用广泛用于修正 GRACE 数据的几个南极冰史模型对该敏感性进行了评估。结果表明，在评估南极 GIA 校正时，岩石圈厚度和上地幔粘度之间存在权衡。所有冰史模型都存在这种权衡；但是，不同模型权衡的原因各不相同。此外，由于南极洲西部和东部的地球结构存在鲜明对比，我们将所采用的冰历史分为南极洲西部和东部两个部分，以研究它们对南极 GIA 校正的贡献。我们考虑了从地震得出的南极洲西部和东部三维地球结构平均得出的一维地球结构。这些结果表明，南极东部和西部载荷的贡献对南极西部和东部地区的 GIA 校正分别没有显著影响，岩石圈厚度和上地幔粘度之间的权衡导致南极西部和东部平均地球模型对南极 GIA 校正的评估差异极小。因此，南极洲下方地球结构的对比可能对整个南极冰原的冰量变化估计影响有限。

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引用次数: 0

Foreword from ILP ILP 前言

IF 2.3 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-08-13 DOI: 10.1016/j.jog.2024.102046

Hans Thybo

引用次数: 0

Deformation and pressure-temperature-time history of the External Tuscan Units in the Northern Apennines (Italy): The case of the Punta Bianca Unit 意大利北亚平宁山脉托斯卡纳外部单元的变形和压力-温度-时间历史：蓬塔比安卡单元案例

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics

Pub Date : 2024-07-31 DOI: 10.1016/j.jog.2024.102045

Chiara Montomoli , Salvatore Iaccarino , Gianfranco Di Vincenzo , Pierre Lanari , Alessandro Petroccia , Rodolfo Carosi

In this study we investigated through a multidisciplinary approach the still poorly known tectono-metamorphic evolution of the Punta Bianca Unit in the Northern Apennines. The Punta Bianca Unit is part of the Tuscan Metamorphic Units, a group of units derived from the Adria passive margin, metamorphosed at different conditions, and forming the backbone of the Northern Apennine belt. We combined meso- and microstructural analyses, ⁴⁰Ar/³⁹Ar white-mica geochronology and multi-equilibrium geothermobarometry from high-resolution X-ray chemical maps, to unravel the deformation and metamorphic history of this part of the belt. Meso- and microstructural data indicate that the Punta Bianca Unit recorded two main phases of ductile deformation (here referred to D_p-1 and D_p) associated with syn-kinematic growth of K-white mica, chlorite, calcite, quartz on the related tectonic foliations (S_p-1 and S_p), followed by a later ductile deformation phase (D_p+1) lacking of metamorphic blastesis. P-T estimates complemented by microstructural data suggest that peak metamorphic conditions reached ∼0.8 GPa and ∼350°C and occurred synchronously with the first deformation phase (D_p-1). Temperature values were also confirmed by Raman spectroscopy of carbonaceous material on selected samples. This stage was followed by the exhumation of the Punta Bianca Unit, as testified by decreasing pressure and temperature down to ∼0.4 GPa and ∼300°C respectively, together with the development of the main foliation (S_p). At the regional scale, the Tuscan Metamorphic Units have been mostly affected by HP-LT metamorphic gradients equilibrated under blueschist-facies conditions (up to ∼1.4 GPa). Results from the present work on the contrary, suggest that the Punta Bianca Unit never reached such HP-LT conditions, testifying that it was deformed at relatively upper structural levels, thus highlighting an important variation in the tectono-metamorphic evolution of the Tuscan Metamorphic Units along strike in the Northern Apennines. ⁴⁰Ar/³⁹Ar laserprobe data (using both the in-situ and step-heating techniques) indicate a minimum age for the onset of continental subduction of ∼20 Ma (D_p-1), which was followed in close succession by exhumation at ∼16 Ma. This approach, if applied to different tectonic units building up the nappe pile of the Northern Apennines, could be successful in better unravelling the tectonic history.

在这项研究中，我们采用多学科方法对北亚平宁山脉蓬塔比安卡单元的构造-变质演化进行了研究，但人们对这一演化仍知之甚少。蓬塔比安卡单元是托斯卡纳变质岩单元的一部分，托斯卡纳变质岩单元是一组源自阿德里亚被动边缘的单元，在不同条件下发生变质，形成了北亚平宁带的主干。我们将介观和微观结构分析、40Ar/39Ar白云母地质年代学和来自高分辨率X射线化学图的多平衡地热测定法结合起来，揭示了该带这一部分的变形和变质历史。介观和微观结构数据表明，蓬塔比安卡单元记录了两个主要的韧性变形阶段（此处称为 Dp-1 和 Dp），与相关构造叶片（Sp-1 和 Sp）上 K-白云母、绿泥石、方解石、石英的同步线状生长有关，随后是缺乏变质爆破作用的后期韧性变形阶段（Dp+1）。P-T估计值与微结构数据相辅相成，表明变质峰值条件达到了∼0.8 GPa和∼350°C，与第一变形阶段（Dp-1）同步发生。温度值还通过对部分样品上的碳质材料进行拉曼光谱分析得到了证实。在这一阶段之后，蓬塔比安卡单元开始出露，压力和温度分别下降到 0.4 GPa 和 300°C，同时出现了主要褶皱（Sp）。在区域范围内，托斯卡纳变质岩单元主要受到在蓝晶-派系条件下平衡的 HP-LT 变质梯度的影响（高达 ∼ 1.4 GPa）。相反，本次研究的结果表明 Punta Bianca 单元从未达到这种 HP-LT 条件，证明它是在相对较高的构造水平上发生变形的，从而突出了托斯卡纳变质岩单元在北亚平宁山脉沿走向的构造-变质演化过程中的一个重要变化。40Ar/39Ar 激光探针数据（使用原位和阶跃加热技术）表明，大陆俯冲开始的最低年龄为 20 Ma (Dp-1)，紧接着是 16 Ma 的掘起。如果将这一方法应用于构成北亚平宁山脉岩层堆积的不同构造单元，则可成功地更好地揭示构造历史。

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