An oceanic core complex and its associated weathered hydrothermal deposit on a ridge-transform intersection zone at 23°S, Southern Mid-Atlantic Ridge

IF 2.6 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
Bing Li , Jixin Wang , Chuanshun Li , Sai Wang , Lei Fan , Jun Ye , Yuan Dang , Quanshu Yan , Xuefa Shi
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Abstract

Numerous investigations into the northern Mid-Atlantic Ridge (the NMAR), a typical slow-spreading mid-ocean ridge, have revealed that NMAR is favorable for the development of long-lived detachment faults and the formation of oceanic core complexes (OCCs). OCCs are often conducive to the development of ultramafic-hosted hydrothermal deposits with significant resource potential. However, as a counterpart of the NMAR on the Southern Hemisphere, the southern Mid-Atlantic Ridge (SMAR), also belonging to the class of slow-spreading ridges, has only received very limited investigation. This prompts the inquiry as to whether the SMAR, like the NMAR, can foster the development of OCC and associated hydrothermal deposit. To address this issue, we present the identification of an OCC (named as Kaifeng OCC) at the intersection of the SMAR and the Martin Vaz transform fault (∼23°S). This discovery is accompanied by evidence detailing a new detachment fault breakaway on an old detachment footwall. Collected samples reveal indications of hydrothermal activity, encompassing (1) residual sulfide containing chalcopyrite within honeycomb-like structures, (2) reddish-brown Fe oxides and atacamite, partially concretized by dolomite, and (3) a dark gray Mn-oxide crust. These mineralogical features indicate the presence of gossans, commonly iron oxide-dominated cover layers that envelope the outer surface of weathered seafloor sulfide deposits, which subsequently undergo modifications due to subsequent hydrothermal activities. Our work proves the existence of OCC and associated hydrothermal deposits at a ridge-transform intersection of the SMAR.

南大西洋中脊 23°S 海脊-变形交汇区的大洋核心复合体及其相关风化热液沉积物
大西洋中脊北部(NMAR)是一个典型的缓慢扩张的大洋中脊,对该海脊的大量调查表明,NMAR 有利于长寿命剥离断层的发育和大洋核心复合体(OCCs)的形成。大洋核心复合体通常有利于开发具有巨大资源潜力的超基性热液矿床。然而,作为南半球 NMAR 的对应海脊,同样属于慢扩张海脊类别的南大西洋中脊(SMAR)只得到了非常有限的研究。这就促使人们去探究南大西洋中脊是否能像北大西洋中脊一样促进OCC及相关热液沉积的发展。为了解决这个问题,我们在 SMAR 与马丁-瓦斯转换断层(南纬 23°)的交汇处发现了一个 OCC(命名为开封 OCC)。这一发现还附有证据,详细说明了在旧的剥离岩脚壁上出现了新的剥离断层断裂。采集的样本显示了热液活动的迹象,包括:(1)蜂窝状结构中残留的含黄铜矿的硫化物;(2)红褐色的铁氧化物和金塔石,部分被白云石凝结;(3)深灰色的锰氧化物结壳。这些矿物学特征表明了格桑的存在,格桑通常是以氧化铁为主的覆盖层,它包裹着风化海底硫化物矿床的外表面,随后由于热液活动而发生变化。我们的工作证明了在 SMAR 的海脊-变形交汇处存在 OCC 和相关热液矿床。
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来源期刊
Marine Geology
Marine Geology 地学-地球科学综合
CiteScore
6.10
自引率
6.90%
发文量
175
审稿时长
21.9 weeks
期刊介绍: Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.
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