Please use this identifier to cite or link to this item:
http://hdl.handle.net/2122/609
Authors: | Paonita, A.* Martelli, M.* |
Title: | Magma dynamics at mid-ocean ridges by noble gas kinetic fractionation: Assessment of magmatic ascent rates | Journal: | Earth and Planetary Science Letters | Series/Report no.: | 1-2/241(2006) | Publisher: | Elsevier | Issue Date: | 2006 | DOI: | 10.1016/j.epsl.2005.10.018 | URL: | http://www.sciencedirect.com/ | Keywords: | Bubble growth MORB Noble gas Kinetic fractionation Modeling |
Subject Classification: | 04. Solid Earth::04.04. Geology::04.04.07. Rock geochemistry 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry 04. Solid Earth::04.08. Volcanology::04.08.01. Gases 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas 04. Solid Earth::04.08. Volcanology::04.08.04. Thermodynamics |
Abstract: | Despite its impact in understanding oceanic crust formation and eruptive styles of related volcanism, magma dynamics at midocean ridges are poorly known. Here, we propose a new method to assess ascent rates of mid-ocean ridge basalt (MORB) magmas,as well as their pre- and sin-eruptive dynamics. It is based on the idea that a rising magma can reach a variable degree of both CO2 supersaturation in melt and kinetic fractionation among noble gases in vesicles in relation to its ascent rate through the crust. To quantify the relationship, we have used a model of multicomponent bubble growth in MORB melts, developed by extending the single-component model of Proussevitch and Sahagian [A.A. Proussevitch, D.L. Sahagian, Dynamics and energetics of bubble growth in magmas: analytical formulation and numerical modeling, J. Geophys. Res. 103 (1998), 18223–18251.] to CO2–He–Ar gas mixtures. After proper parameterization, we have applied it to published suites of data having the required features (glasses from Pito Seamount and mid-Atlantic ridges). Our results highlight that the investigated MORB magmas display very different ranges of ascent rates: slow rises of popping rock forming-magmas that cross the crust (0.01–0.5 m/s), slightly faster rates of energetic effusions (0.1–1 m/s), up to rates of 1–10 m/s which fall on the edge between lava effusion and Hawaiian activity. Inside a single plumbing system, very dissimilar magma dynamics highlight the large differences in compressive stress of the oceanic crust on a small scale. Constraints on how the systems of ridges work, as well as the characteristics of the magmatic source, can also be obtained. Our model shows how measurements of both the dissolved gas concentration in melt and the volatile composition of vesicles in the same sample are crucial in recognizing the kinetic effects and definitively assessing magma dynamics. An effort should be made to correctly set the studied samples in the sequence of volcanic submarine deposits where they are collected. Enhanced knowledge of a number of physical properties of gas-bearing MOR magmas is also required, mainly noble gas diffusivities, to describe multicomponent bubble growth at a higher confidence level. |
Appears in Collections: | Article published / in press |
Files in This Item:
File | Description | Size | Format | Existing users please Login |
---|---|---|---|---|
Paonita et al. EPSL 2005.pdf | Main article | 679.08 kB | Adobe PDF | |
Redirect Elsevier.html | Redirect-Elsevier | 539 B | HTML | View/Open |
WEB OF SCIENCETM
Citations
20
checked on Feb 10, 2021
Page view(s) 20
262
checked on Mar 27, 2024
Download(s)
63
checked on Mar 27, 2024