Multiple Fluid Alterations in the Matrial Subsurface Recorded By Nakhlites

Authors: Agata Krzesinska (Natural History Museum) , Paul Schofield (Natural History Museum) , Tina Geraki (Diamond Light Source) , Joe Michalski (University of Hong Kong) , Caroline Smith (Natural History Museum)
Co-authored by industrial partner: No

Type: Conference Paper
Conference: 80th Annual Meeting of the Meteoritical Society
Peer Reviewed: No

State: Published (Approved)
Published: July 2017
Diamond Proposal Number(s): 14910 , 16067

Open Access Open Access

Abstract: Nakhlites are martian pyroxenites that crystallized in a shallow intrusion or lava flow(s) during the Amazonian period, ~1.3 Ga [1]. They host amorphous and/or nanocrystalline hydrous Fe,Mg-silicates and a range of salt minerals that clearly formed via water-rock interactions in the subsurface of Mars [e.g., 2,3,4] as recently as ~680 Ma [5]. The nature of the aqueous event(s) that triggered the alterations, especially the mechanisms by which the secondary minerals formed are, however, not fully recognized. The most comprehensive model suggests that all the secondary minerals were formed by a single episodic event and were deposited from a brine that was derived from a low-T hydrothermal source [6]. Trace element signatures of some alteration minerals [3] may in turn suggest evaporation of a surface derived brine such as flood waters. Nanostructural studies [4] instead reveal that carbonates may have formed by serpentinization and carbonation of olivine via reaction with atmosphericderived gas. The majority of interpretations are, however, based mainly on the observation of Fe,Mg-silicates, while the salt minerals, and especially their textures, have been studied far less. Our study is concerned with the reconstruction of fluid flow(s) and alteration/replacement histories recorded by the salt minerals in nakhlites. We focus on their chemical and textural relationships to the primary minerals, each other, the hydrous Fe,Mg-silicates and the fracture systems. Moreover, we have undertaken this study with no (or minimal) invasive or destructive sampling.

Journal Keywords: Nakhlites, Mars, fluid flow

Subject Areas: Earth Science

Instruments: I18-Microfocus Spectroscopy