Haroon
Amir
Haroon
Amir
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ArticleOffshore freshened groundwater in continental margins(American Geophysical Union, 2020-11-20) Micallef, Aaron ; Person, Mark ; Berndt, Christian ; Bertoni, Claudia ; Cohen, Denis ; Dugan, Brandon ; Evans, Rob L. ; Haroon, Amir ; Hensen, Christian ; Jegen, Marion ; Key, Kerry ; Kooi, Henk ; Liebetrau, Volker ; Lofi, Johanna ; Mailloux, Brian J. ; Martin-Nagle, Renée ; Michael, Holly A. ; Müller, Thomas ; Schmidt, Mark ; Schwalenberg, Katrin ; Trembath-Reichert, Elizabeth ; Weymer, Bradley ; Zhang, Yipeng ; Thomas, Ariel T.First reported in the 1960s, offshore freshened groundwater (OFG) has now been documented in most continental margins around the world. In this review we compile a database documenting OFG occurrences and analyze it to establish the general characteristics and controlling factors. We also assess methods used to map and characterize OFG, identify major knowledge gaps, and propose strategies to address them. OFG has a global volume of 1 × 106 km3; it predominantly occurs within 55 km of the coast and down to a water depth of 100 m. OFG is mainly hosted within siliciclastic aquifers on passive margins and recharged by meteoric water during Pleistocene sea level lowstands. Key factors influencing OFG distribution are topography-driven flow, salinization via haline convection, permeability contrasts, and the continuity/connectivity of permeable and confining strata. Geochemical and stable isotope measurements of pore waters from boreholes have provided insights into OFG emplacement mechanisms, while recent advances in seismic reflection profiling, electromagnetic surveying, and numerical models have improved our understanding of OFG geometry and controls. Key knowledge gaps, such as the extent and function of OFG, and the timing of their emplacement, can be addressed by the application of isotopic age tracers, joint inversion of electromagnetic and seismic reflection data, and development of three-dimensional hydrological models. We show that such advances, combined with site-specific modeling, are necessary to assess the potential use of OFG as an unconventional source of water and its role in sub-seafloor geomicrobiology.
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ArticleMagnetic and gravity surface geometry inverse modeling of the TAG active mound(American Geophysical Union, 2021-09-29) Galley, Christopher ; Lelièvre, Peter G. ; Haroon, Amir ; Graber, Sebastian ; Jamieson, John W. ; Szitkar, Florent ; Yeo, Isobel A. ; Farquharson, Colin ; Petersen, Sven ; Evans, Rob L.Seafloor massive sulfide deposits form in remote environments, and the assessment of deposit size and composition through drilling is technically challenging and expensive. To aid the evaluation of the resource potential of seafloor massive sulfide deposits, three-dimensional inverse modeling of geophysical potential field data (magnetic and gravity) collected near the seafloor can be carried out to further enhance geologic models interpolated from sparse drilling. Here, we present inverse modeling results of magnetic and gravity data collected from the active mound at the Trans-Atlantic Geotraverse hydrothermal vent field, located at 26°08′N on the Mid-Atlantic Ridge, using autonomous underwater vehicle and submersible surveying. Both minimum-structure and surface geometry inverse modeling methods were utilized. Through deposit-scale magnetic modeling, the outer extent of a chloritized alteration zone within the basalt host rock below the mound was resolved, providing an indication of the angle of the rising hydrothermal fluid and the depth and volume of seawater/hydrothermal mixing zone. The thickness of the massive sulfide mound was determined by modeling the gravity data, enabling the tonnage of the mound to be estimated at 2.17 ± 0.44 Mt through this geophysics-based, noninvasive approach.
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ArticleThe coastal transition zone is an underexplored frontier in hydrology and geoscience(Nature Research, 2022-12-23) Weymer, Bradley A. ; Everett, Mark E. ; Haroon, Amir ; Jegen-Kulcsar, Marion ; Micallef, Aaron ; Berndt, Christian ; Michael, Holly A. ; Evans, Rob L. ; Post, VincentWe have better maps of the surfaces of Venus, Mars, and the Moon than of the Earth’s seafloor. There is even less information available about the geologic structure below the seafloor. In particular, the transition zone deep beneath and crossing the coastline is a very poorly studied frontier resulting from limitations of technology and logistical barriers. Here, we point out the significance of this region for understanding fundamental geologic processes, geohazards, and especially coastal aquifers. One prominent example is the increasing awareness of the importance of groundwater exchange between land and sea. This Perspective defines the region beneath the coastal transition zone, or coastal white ribbon as an underexplored frontier, and highlights the need for characterization of this critical region to depths of tens of km. We discuss available geophysical methods and their limitations with coastal groundwater used as the primary illustration. Advances in geophysical and drilling technology, coupled with numerical modeling, are needed to enable better accounting of this poorly understood component of the geosphere.
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ArticleAutomated seafloor massive sulfide detection through integrated image segmentation and geophysical data analysis: Revisiting the TAG hydrothermal field(American Geophysical Union, 2023-12-19) Haroon, Amir ; Paasche, Hendrik ; Graber, Sebastian ; Petersen, Sven ; Attias, Eric ; Jegen, Marion ; Gehrmann, Romina ; Holz, Sebastian ; Klischies, MeikeAccessible seafloor minerals located near mid-ocean ridges are noticed to mitigate the projected metal demands of the net-zero energy transition, promoting growing interest in quantifying the global distributions of seafloor massive sulfides (SMS). Mineral potentials are commonly estimated using geophysical and geological data that lastly rely on additional confirmation studies using sparsely available, locally limited, seafloor imagery, grab samples, and coring data. This raises the challenge of linking in situ confirmation data to geophysical data acquired at disparate spatial scales to obtain quantitative mineral predictions. Although multivariate data sets for marine mineral research are incessantly acquired, robust, integrative data analysis requires cumbersome workflows and experienced interpreters. We introduce an automated two-step machine learning approach that integrates the mound detection through image segmentation with geophysical data. SMS predictors are subsequently clustered into distinct classes to infer marine mineral potentials that help guide future exploration. The automated workflow employs a U-Net convolutional neural network to identify mound structures in bathymetry data and distinguishes different mound classes through the classification of mound architectures and magnetic signatures. Finally, controlled source electromagnetic data are utilized together with in situ sampling data to reassess predictions of potential SMS volumes. Our study focuses on the Trans-Atlantic Geotraverse area, which is among the most explored SMS areas worldwide and includes 15 known SMS sites. The automated workflow classifies 14 of the 15 known mounds as exploration targets of either high or medium priority. This reduces the exploration area to less than 7% of the original survey area from 49 to 3.1 km2.