Chemical alteration of sediments on early stage of existing of hydrothermal systems in spreading zones of sedimented ridges (hydrothermal field “Dead Dog”, Middle Valley, Juan de Fuca Ridge)

Alexandra Khakhina,Yurii Konovalov,Valeriya Churkina,Victor Kurnosov,Konstantin Galin,O Chudaev,R Harmon,R Millot,O Shouakar-Stash,Y Kharaka

doi:10.1051/e3sconf/20199808011

Abstract

In sediments from Holes DSDP 858B, D, F, located near the active hot vent on the thermal field “Dead Dog” in the northern part of the Juan de Fuca Ridge, Middle Valley, a redistribution of chemical elements occurs as a result of solution-rock interaction. During this process, the increase/decrease of their content in hydrothermally altered sediments inversely reflects the decrease/increase of their content in the solution. Nonregular distribution of microelements and REE’s in hydrothermally altered sediments, like a layer pie, reflects the participation of both ascending hydrothermal fluids and lateral flows of hydrothermal solutions in alteration of chemical composition of sediments.

Highlights

Middle Valley of the Juan de Fuca Ridge represents a model of oceanic crust formation by the rifting of continental margins [1, 2], when thick masses of sediments deposit in spreading rifts with a high rate of speed (1200 - 2300 m/mln.y) and covers spreading zones with hydrothermal systems
Holes 858A, B, C, D, F were drilled in the northern part of Juan de Fuca Ridge (Middle Valley), on the hydrothermal field "Dead Dog", during Leg 139 ODP
They were located in a modern hydrothermal system covered with Holocene and Upper Pleistocene turbidites interbedded with hemipelagic sediments [1]

Summary

Introduction

Middle Valley of the Juan de Fuca Ridge represents a model of oceanic crust formation by the rifting of continental margins [1, 2], when thick masses of sediments deposit in spreading rifts with a high rate of speed (1200 - 2300 m/mln.y) and covers spreading zones with hydrothermal systems. Holes 858A, B, C, D, F were drilled in the northern part of Juan de Fuca Ridge (Middle Valley), on the hydrothermal field "Dead Dog", during Leg 139 ODP. They were located in a modern hydrothermal system covered with Holocene and Upper Pleistocene turbidites interbedded with hemipelagic sediments [1]. Only one similar site with deep-sear holes drilled is known. It is Central Hill in Escanaba Trough, Gorda Ridge, Pacific Ocean [3]

Objects and methods

Results

Conclusions