干旱区生态环境知识资源中心(Arid): When a mid-ocean ridge encroaches a continent: Seafloor-type hydrothermal activity in Lake Asal (Afar Rift)

Arid

DOI	10.1016/j.chemgeo.2021.120126
	When a mid-ocean ridge encroaches a continent: Seafloor-type hydrothermal activity in Lake Asal (Afar Rift)
	Dekov, V. M.; Gueguen, B.; Yamanaka, T.; Moussa, N.; Okumura, T.; Bayon, G.; Liebetrau, V; Yoshimura, T.; Kamenov, G.; Araoka, D.; Makita, H.; Sutton, J.
通讯作者	Dekov, VM (corresponding author), Tokyo Univ Marine Sci & Technol, Dept Ocean Sci, Minato Ku, 4-5-7 Konan, Tokyo 1088477, Japan.
来源期刊	CHEMICAL GEOLOGY
ISSN	0009-2541
EISSN	1872-6836
出版年	2021
卷号	568
英文摘要	At the place where the submarine Aden Ridge encroaches on the African continent and interacts with the East African Rift system, two small basins form: Ghoubbet-al-Kharab and Lake Asal. Whereas Ghoubbet-al-Kharab is connected to the open ocean, Lake Asal is a typical example of oceanic embryo, which is defined as a system that is detached from the ocean, but has features of a marine basin with an oceanic type crust and a seawaterbased water body. In order to shed light on the source of water, type of hydrothermal activity and hydrothermal deposits, and controls on the water chemistry in an oceanic embryo, we undertook a mineralogicalgeochemical study of the lake water, hydrothermal fluids and hydrothermal carbonate deposits of Lake Asal. The geochemical analyses of lake water and hydrothermal fluids show that Lake Asal (located in an arid zone with strong evaporation and with no riverine input) is fed by seafloor-type hydrothermal fluids according to the following scenario: percolation of seawater along faults and cracks of extension in the rift, reaction of seawater with the hot basaltic rocks and hydrothermal fluid generation, discharge of the hydrothermal fluid in the Asal depression and accumulation of the Lake Asal water body. The fluid venting at the Lake Asal bottom is a mixture of 97% end-member hydrothermal fluid and 3% lake water. The calculated end-member hydrothermal fluid of this oceanic embryo is poorer in metals than the seafloor hydrothermal fluids of an open and evolved ocean. In addition to the seawater/rock interaction, the chemistry of Lake Asal is also controlled by evaporation leading to hyper salinity. In a hyper saline water body a number of hydrothermally supplied metals are stabilized as chloride complexes and accumulate. This results in a metal rich and mildly acidic embryonic ocean. Unlike an open and evolved modern ocean, the embryonic ocean located in an arid zone has heavy C and O isotope composition and light Zn and Fe isotope composition. Calcium isotope compositions of both types of ocean are similarly heavy. There are two genetically different sources of elements to the Lake Asal that are vertically separated: hydrothermal (lower, or bottom) and aeolian (upper, or surficial). Another important control on the lake water chemistry is the formation of carbonate spires at the lake bottom. Ca-carbonate precipitation immobilizes substantial amount of hydrothermally supplied Ca and drives up the (Mg/Ca) mol of the lake water. Increasing (Mg/Ca) mol of the evolving lake water leads to changes in the mineralogy of spires: from low-Mg calcite to aragonite. Thus, the spire formation exerts a self-control on its mineralogy. Carbonate spire deposition affects also the Ca, Zn and Fe isotope composition of the lake water through adsorption or/and co-precipitation induced isotope fractionation.
英文关键词	Asal Rift Carbonate spires C-O-Ca-Fe-Zn-Sr-U-Th isotopes Continental rift Embryonic ocean Seafloor hydrothermal activity
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000636052200007
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
来源机构	French National Research Institute for Sustainable Development ; E17
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/349830
作者单位	[Dekov, V. M.; Yamanaka, T.; Makita, H.] Tokyo Univ Marine Sci & Technol, Dept Ocean Sci, Minato Ku, 4-5-7 Konan, Tokyo 1088477, Japan; [Gueguen, B.] Univ Brest, UMR 6538, CNRS, Lab Geosci Ocean, F-29280 Plouzane, France; [Gueguen, B.] Univ Brest, CNRS, UMS 3113, F-29280 Plouzane, France; [Moussa, N.] Ctr Etud & Rech Djibouti CERD, IST, BP 486,Route Aeroport, Haramous, Djibouti; [Okumura, T.] Kochi Univ, Ctr Adv Marine Core Res, Nanko Ku, 200 Monobe Otsu, Kochi 7838502, Japan; [Bayon, G.] IFREMER, Marine Geosci Unit, F-29280 Plouzane, France; [Liebetrau, V] Helmholtz Ctr Ocean Res Kiel, GEOMAR, Wischhofstr 1-3, D-24124 Kiel, Germany; [Yoshimura, T.] Japan Agcy Marine Earth Sci & Technol JAMSTEC, Biogeochem Program, Res Inst Marine Resources Utilizat, 2-15 Natsushima Cho, Yokosuka, Kanagawa 2370061, Japan; [Kamenov, G.] Univ Florida, Dept Geol Sci, 241 Williamson Hall, Gainesville, FL 32611 USA; [Araoka, D.] Natl Inst Adv Ind Sci & Technol, Cent 7, Geol Survey Japan GSJ, 1-1-1 Higashi, Tsukuba, Ibaraki 305...
推荐引用方式 GB/T 7714	Dekov, V. M.,Gueguen, B.,Yamanaka, T.,et al. When a mid-ocean ridge encroaches a continent: Seafloor-type hydrothermal activity in Lake Asal (Afar Rift)[J]. French National Research Institute for Sustainable Development, E17,2021,568.
APA	Dekov, V. M..,Gueguen, B..,Yamanaka, T..,Moussa, N..,Okumura, T..,...&Sutton, J..(2021).When a mid-ocean ridge encroaches a continent: Seafloor-type hydrothermal activity in Lake Asal (Afar Rift).CHEMICAL GEOLOGY,568.
MLA	Dekov, V. M.,et al."When a mid-ocean ridge encroaches a continent: Seafloor-type hydrothermal activity in Lake Asal (Afar Rift)".CHEMICAL GEOLOGY 568(2021).