Geodynamic controls on clastic-dominated base metal deposits

IF 3.2 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Solid Earth Pub Date : 2024-08-06 DOI:10.5194/se-15-921-2024
Anne C. Glerum, Sascha Brune, Joseph M. Magnall, Philipp Weis, Sarah A. Gleeson
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Abstract

Abstract. To meet the growing global demand for metal resources, new ore deposit discoveries are required. However, finding new high-grade deposits, particularly those not exposed at the Earth's surface, is very challenging. Therefore, understanding the geodynamic controls on the mineralizing processes can help identify new areas for exploration. Here we focus on clastic-dominated Zn–Pb deposits, the largest global resource of zinc and lead, which formed in sedimentary basins of extensional systems. Using numerical modelling of lithospheric extension coupled with surface erosion and sedimentation, we determine the geodynamic conditions required to generate the rare spatiotemporal window where potential metal source rocks, transport pathways, and host sequences are present. We show that the largest potential metal endowment can be expected in narrow asymmetric rifts, where the mineralization window spans about 1–3 Myr in the upper ∼ 4 km of the sedimentary infill close to shore. The narrow asymmetric rift type is characterized by rift migration, a process that successively generates hyper-extended crust through sequential faulting, resulting in one wide and one narrow conjugate margin. Rift migration also leads to (1) a sufficient life span of the migration-side border fault to accommodate a thick submarine package of sediments, including coarse (permeable) continental sediments that can act as source rock; (2) rising asthenosphere beneath the thinned lithosphere and crust, resulting in elevated temperatures in these overlying sediments that are favourable for leaching metals from the source rock; (3) the deposition of organic-rich sediments that form the host rock at shallower burial depths and lower temperatures; and (4) the generation of smaller faults that cut the major basin created by the border fault and provide additional pathways for focused fluid flow from source to host rock. Wide rifts with rift migration can have similarly favourable configurations, but these occur less frequently and less potential source rock is produced, thereby limiting potential metal endowment. In simulations of narrow symmetric rifts, the conditions to form ore deposits are rarely fulfilled. Based on these insights, exploration programmes should prioritize the narrow margins formed in asymmetric rift systems, in particular regions within several tens of kilometres from the paleo-shoreline, where we predict the highest-value deposits to have formed.
碎屑岩为主的贱金属矿床的地球动力控制
摘要为了满足全球对金属资源日益增长的需求,需要发现新的矿藏。然而,寻找新的高品位矿床,尤其是那些未暴露在地表的矿床,是非常具有挑战性的。因此,了解成矿过程的地球动力学控制有助于确定新的勘探区域。在此,我们将重点放在以碎屑岩为主的锌铅矿床上,这些矿床是全球最大的锌铅资源,形成于伸展系统的沉积盆地中。通过对岩石圈延伸与地表侵蚀和沉积作用的数值模拟,我们确定了产生罕见的时空窗口所需的地球动力条件,在这些时空窗口中存在着潜在的金属源岩、运移途径和母岩序列。我们的研究表明,在狭窄的非对称裂谷中,潜在的金属禀赋可能最大,在靠近海岸的沉积填充物上部∼ 4 公里处,成矿窗口的时间跨度约为 1-3 Myr。窄非对称裂谷类型的特点是裂谷迁移,这一过程通过连续的断层先后产生超延伸地壳,形成一宽一窄的共轭边缘。裂谷迁移还导致:(1) 迁移侧边界断层的寿命足以容纳厚厚的海底沉积物包,包括可作为源岩的粗糙(可渗透)大陆沉积物;(2) 在变薄的岩石圈和地壳下的星体层上升,导致这些上覆沉积物的温度升高,有利于从源岩中沥滤金属;(3) 富含有机质的沉积物沉积,形成埋藏深度较浅、温度较低的寄主岩;以及 (4) 产生较小的断层,切割边界断层形成的主要盆地,为流体从源岩集中流向寄主岩提供更多途径。具有裂谷迁移的宽断裂也可能具有类似的有利构造,但这种构造出现的频率较低,产生的潜在源岩也较少,从而限制了潜在的金属禀赋。在窄对称裂谷的模拟中,形成矿床的条件很少得到满足。基于这些认识,勘探计划应优先考虑非对称裂谷系统中形成的狭窄边缘,特别是距离古海岸线几十公里的区域,我们预测价值最高的矿床就形成于这些区域。
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来源期刊
Solid Earth
Solid Earth GEOCHEMISTRY & GEOPHYSICS-
CiteScore
6.90
自引率
8.80%
发文量
78
审稿时长
4.5 months
期刊介绍: Solid Earth (SE) is a not-for-profit journal that publishes multidisciplinary research on the composition, structure, dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. The journal invites contributions encompassing observational, experimental, and theoretical investigations in the form of short communications, research articles, method articles, review articles, and discussion and commentaries on all aspects of the solid Earth (for details see manuscript types). Being interdisciplinary in scope, SE covers the following disciplines: geochemistry, mineralogy, petrology, volcanology; geodesy and gravity; geodynamics: numerical and analogue modeling of geoprocesses; geoelectrics and electromagnetics; geomagnetism; geomorphology, morphotectonics, and paleoseismology; rock physics; seismics and seismology; critical zone science (Earth''s permeable near-surface layer); stratigraphy, sedimentology, and palaeontology; rock deformation, structural geology, and tectonics.
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