Depth-Dependent Chlorine Cycling at the Magmatic-Hydrothermal Interface of Mid-Ocean Ridges: Insights from Hornfelsic Diabase

Clicks: 13
ID: 323039
2026
Free PDF
Article Quality & Performance Metrics
Overall Quality
Not rated
Combines reader engagement with the AI quality analysis. This article has not been analysed, so there is no overall score — reader engagement is measured and shown alongside.
AI Quality Assessment
Not analyzed
Readership in this journal
Emerging

Ranked #14 of 66 articles by views in journal of petrology

Most read Least read

Bar heights use a square-root scale.

Mint this article as an NFT
Not yet minted

Create a permanent, verifiable on-chain record of this article on the Scimatic Network. The NFT is held in your Journament account, and you can withdraw it to your own wallet at any time.

5 SUSD one-off · no wallet required
Sign in to mint
Abstract
Abstract The conductive boundary layer (CBL) at the magmatic-hydrothermal interface of mid-ocean ridges (MORs) regulates the fundamental exchange of heat and chemical species between cooling magmas and circulating seawater. While this interface is well-documented at shallow, fast-spreading ridges and in ophiolites, its nature in deep-seated magmatic environments—particularly along slow-spreading ridge segments hosting oceanic core complexes (OCCs)—remains poorly constrained. Here, we investigate the physicochemical properties of this interface through a detailed microstructural, geochemical, and fluid inclusion analysis of hornfelsic diabase, the primary constituent of the CBL, recovered from the Onnuri OCC on the Central Indian Ridge. Our results characterize two distinct lithologies: hornblende hornfelsic and pyroxene hornfelsic diabase. Clinopyroxene geothermometry yields peak metamorphic temperatures of 815–987 °C, with evidence of localized hydrous partial melting and the formation of amphibole-rich diorite. Despite these intense thermal conditions, the Onnuri hornfels exhibits remarkably low chlorine (Cl) signatures in both amphiboles (< 663 ppm) and fluid inclusions (2.0–5.0 wt.% NaCl eq.), reflecting interaction with fluids of seawater-like salinity. This geochemical signature contrasts sharply with the high-Cl brines and Cl-rich amphiboles typical of shallow fast-spreading systems. We demonstrate that this divergence is fundamentally rooted in the pressure-regulated phase behavior of seawater. Seawater P-T phase analysis identifies a critical hydrostatic pressure threshold of 80-100 MPa; beyond this limit, phase separation is effectively suppressed, whereas at lower pressures, it becomes increasingly pronounced as pressure declines. Consequently, the high-pressure regime prevents the formation of a basal brine layer—promoting interaction with low-salinity, seawater-like fluids—while the low-pressure regime facilitates brine accumulation. To evaluate whether this mechanism can be applied on a global scale, we performed a meta-analysis of MORB chemistry and hydrothermal vent datasets. Our analysis of global MORB datasets demonstrates that magma storage depth exerts the ultimate control over crustal Cl assimilation, with long-term, segment-scale magmatic flux operating as the underlying driver of this vertical architecture. Furthermore, hydrothermal vent fluid data exhibit a corresponding depth-dependent variability, with Cl concentrations stabilizing near seawater values as heat source depth increases. By synthesizing these multi-disciplinary constraints, we propose a unified, depth-dependent model for Cl cycling at the magmatic-hydrothermal interface. We conclude that the emplacement depth of the magmatic heat source, governed by segment-wide magmatic flux, serves as the primary determinant of the hydrostatic pressure of the hydrothermal cell, thereby controlling subseafloor brine formation, the extent of crustal Cl assimilation, and the chemical stability of hydrothermal vent fluids in the global MOR oceanic crust.
Reference Key
openalex_W7171858312 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors Sarang Choi, Jung‐Woo Park, Sunghwan Im, Tong Ha Lee, Jung Hun Seo, Changkun Park, Hwayoung Kim, Jonguk Kim
Journal journal of petrology
Year 2026
DOI
10.1093/petrology/egag064
URL
https://doi.org/10.1093/petrology/egag064
Keywords Keywords not found

Citations

No citations found. To add a citation, contact the admin at info@scimatic.org

Comments

No comments yet. Be the first to comment on this article.