NASAs Mars Science Laboratory Curiosity rover has been exploring Vera Rubin ridge (VRR), part of the Murray formation in Gale crater, Mars, between sol 1809 and 2302. Evidence for Fe-oxides and phyllosilicates in mineralogical and geochemical data for this region was returned by Curiosity [1-5]. We applied thermochemical modeling to con-strain the formation conditions of the phyllosilicate-hematite assemblage identified on and below VRR. Average alteration compositions for the Murray formation on and below VRR were derived using CheMin and APXS data. These compositions were reacted with Gale Portage Water (GPW) between 25100 C and for 10% and 50% Fe3+/Fetot of the host rock [6]. Here we summarize models run at 50 C and 10% Fe3+/Fetot for alteration compositions derived from Murray host rock compositions

Achilles, C.N.

Bedford, C.C.

Bridges, J.C.

Fraeman, A.A.

Hicks, L.J.

Kirnbauer, T.

Mangold, N.

McAdam, A.

Parnell, J.

Rampe, E.B.

Reed, M.H.

Schwenzer, S.P.

Turner, S.M.R.

English

Hicks, L. J.

Rampe, E. B.

Bridges, J. C.

Reed, M. H.

Schwenzer, S. P.

Fraeman, A. A.

Turner, S. M. R.

Bedford, C. C.

Achilles, C. N.

NASA Technical Reports Server

ENHANCED GROUNDWATER FLOW ON AND BELOW VERA RUBIN RIDGE, THE MURRAY 
FORMATION, GALE CRATER: EVIDENCE FROM THERMOCHEMICAL MODELING.  S.M.R. Turner1, 
S.P. Schwenzer1, J.C. Bridges2, E.B. Rampe3, C.C. Bedford3,4,5, C.N. Achilles6, A. McAdam6, N. Mangold7, L.J. 
Hicks2, J. Parnell8, T. Kirnbauer9, A.A. Fraeman10, and M.H. Reed11. 1AstrobiologyOU, School of Environment, 
Earth and Ecosystem Sciences, The Open University, UK, (stuart.turner@open.ac.uk). 2Space Research Centre, 
School of Physics and Astronomy, University of Leicester, UK. 3NASA Johnson Space Center, USA. 4School of 
Physical Sciences, The Open University, UK. 5Lunar and Planetary Institute, USRA, USA. 6NASA Goddard Space 
Flight Center, USA. 7Laboratoire de Planétologie et Géodynamique, UMR6112 CNRS, Université de Nantes, Uni-
versité Angers, France. 8School of Geosciences, University of Aberdeen, UK. 9TH Georg Agricola, Bochum, Ger-
many. 10Jet Propulsion Laboratory, California Institute of Technology, USA. 11Department of Earth Sciences, Uni-
versity of Oregon, USA. 
 
Introduction:  NASA’s Mars Science Laboratory 
Curiosity rover has been exploring Vera Rubin ridge 
(VRR), part of the Murray formation in Gale crater, 
Mars, between sol 1809 and 2302. Evidence for Fe-
oxides and phyllosilicates in mineralogical and geo-
chemical data for this region was returned by Curiosity 
[1-5]. We applied thermochemical modeling to con-
strain the formation conditions of the phyllosilicate-
hematite assemblage identified on and below VRR. 
Average alteration compositions for the Murray for-
mation on and below VRR were derived using CheMin 
and APXS data. These compositions were reacted with 
Gale Portage Water (GPW) between 25–100 °C and 
for 10% and 50% Fe3+/Fetot of the host rock [6]. Here 
we summarize models run at 50 °C and 10% Fe3+/Fetot 
for alteration compositions derived from Murray host 
rock compositions. 
Modeling:  CHIM-XPT is a program for compu-
ting multicomponent heterogeneous chemical equilib-
ria in aqueous-mineral-gas systems [7], and was previ-
ously used in fluid-rock interaction studies for Gale 
crater [8-12]. Each step calculates equilibrium between 
a user-defined fluid and dissolved rock, meaning that 
each step can be interpreted independently. The wa-
ter/rock ratio (W/R) in CHIM-XPT is the ratio of in-
coming fluid to reacted rock. Here, the models focus 
on 1–100,000 W/R. 
The Starting Fluid. GPW was selected as the start-
ing fluid, and has previously been used in thermo-
chemical modeling studies [9,10,12]. GPW was de-
rived from equilibrium mediation between a brine and 
rocks of the Gale area [9]. The solution is initially oxi-
dizing (all S species as SO42-), and the redox in the 
fluid is controlled by the SO42-/HS- pair. The redox of 
the system throughout each model is dependent on the 
Fe3+/Fetot ratio of the host rock.  
The Starting Rock. The composition of the altera-
tion component in the Murray formation on and below 
VRR, along with an overall alteration composition, 
was derived by combining data returned by APXS and 
CheMin for the drill holes: Oudam (drilled on sol 
1361), Marimba (sol 1422), Quela (sol 1464), Sebina 
(sol 1495), Stoer (sol 2136), Highfield (sol 2223), and 
Rock Hall (sol 2261) [13]. Using crystal chemistries 
derived for the magmatic minerals and mineral abun-
dances determined using CheMin data, compositional 
oxide wt.% contributions from the magmatic phases 
were subtracted from the bulk APXS measurements. 
Ca-sulfate contributions were also excluded as these 
formed during late diagenesis [10,14]. 
Results: Thermochemical modeling was carried 
out for the temperature range 25–100 °C [6]. Here we 
compare model results for alteration compositions de-
rived for VRR (Fig. 1) and below VRR (Fig. 2).  
Figs. 1 and 2 show >10 wt.% hematite precipitating 
for ≥10,000 W/R for both alteration compositions at 
50 °C and 10% Fe3+/Fetot.  
Comparing summed clay mineral / hematite ratios 
(C/H) at 100, 1,000 and 10,000 W/R in the models in 
Figs. 1 and 2 with C/H from CheMin data suggests that 
the models at 10,000 W/R are comparable to Curiosity 
observations [6]. For 10% Fe3+/Fetot these C/H  values 
are 1.2 and 3.0 for on and below VRR, respectively. 
C/H values change to 1.2 and 1.7 for 50% Fe3+/Fetot. 
Comparable C/H values extracted from CheMin data 
are 1.9 ± 0.7 and 2.4 ± 0.3 for on and below VRR, re-
spectively. When summing all Fe-oxides the value for 
VRR changes to 0.8 ± 0.3 due to akaganeite in Rock 
Hall.  
Discussion: The models presented here and by [6] 
indicate potential formation conditions for the clay 
mineral-hematite assemblage in the Murray formation 
on and below VRR. To assess the comparability with 
previous modeling and Curiosity observations, the 
phyllosilicate chemical composition was summed for 
10,000, 1,000 and 100 W/R models and shown on a 
ternary plot in Fig. 3. Fig. 3 shows the modeled phyllo-
silicates at 10,000 W/R are close to Sheepbed unit 
model saponite [9], with the models trending towards 
nontronite compositions at 1,000 and 100 W/R [6]. 
Note that we assume the akaganeite and jarosite de-
tected by CheMin in the Murray formation to be the 
result of later alteration where Fe was remobilized 
from the modeled mineral assemblages [6]. 
2481.pdf51st Lunar and Planetary Science Conference (2020)
https://ntrs.nasa.gov/search.jsp?R=20200001795 2020-05-24T04:18:35+00:00Z
 
Fig. 1: CHIM-XPT thermochemical model for the VRR 
Murray alteration composition reacted with GPW. The 
model was run at 50 °C and 0.1 Fe3+/Fetot. 
 
Fig. 2: CHIM-XPT thermochemical model for the pre-
VRR Murray alteration composition reacted with 
GPW. The model was run at 50 °C and 0.1 Fe3+/Fetot. 
Conclusions: Results presented here and by [6] 
show how derived alteration compositions for the Mur-
ray formation can be reacted with a dilute brine (GPW) 
to produce an alteration mineral assemblage compara-
ble with the clay mineral-hematite assemblage ob-
served in the Murray formation on and below VRR. 
Results presented in this abstract focus on models run 
at 50 °C, however additional models show that tem-
peratures can extend to 100 °C, with pH ranging be-
tween 7.9 and 9.3 at ~10,000 W/R [6]. This modeling 
suggests that the alteration mineral assemblage ob-
served in the Murray formation is due to enhanced 
groundwater flow through this part of the Gale sedi-
mentary sequence, compared to previous observations 
and modeling in the Bradbury group at Yellowknife 
bay [9]. 
 
Fig. 3: Mg-Si+Al-Fetot at. ternary plot. Results at 
10,000 (red), 1,000 (green) and 100 (blue) W/R from 
the thermochemical models in this abstract and in [6] 
are plotted with some additional data from other 
sources for comparison. CHIM-XPT results for the 
Sheepbed unit from [9] at 100 and 1,000 W/R are 
shown for comparison. 
References: [1] Rampe E.B. et al. (2017). EPSL, 471, 172-
185. [2] Morrison S.M. et al. (2018). Am. Mineral. 103(6), 857-871. 
[3] Bristow T.F. et al. (2018). Science Advances (6), eaar3330. [4] 
Achilles C.N. et al. (submitted). Mineralogy of ancient fluvial-
lacustrine sediments in Gale crater, Mars: Evidence for multiple 
diagenetic episodes. Submitted to JGR: Planets. [5] Rampe E.B. et 
al. (submitted). Mineralogy of Vera Rubin ridge from the Mars Sci-
ence Laboratory CheMin instrument. Submitted to JGR: Planets. [6] 
Turner S.M.R. et al. (in prep). Fluid-Rock Reactions in the Murray 
Formation, including Vera Rubin ridge, Gale crater, Mars. To be 
submitted to JGR: Planets. [7] Reed M.H. et al. (2010). User Guide 
for CHIM-XPT: A Program for Computing Reaction Processes in 
Aqueous-Mineral-Gas Systems and MINTAB Guide. 71p., Universi-
ty of Oregon, Eugene. [8] Bridges J.C. et al. (2015). LPSC 46, ab-
stract #1769. [9] Bridges J.C. et al. (2015). JGR: Planets, 120, 1-19. 
[10] Schwenzer S.P. et al. (2016). MAPS, 51(11), 2175-2202. [11] 
Schieber J. et al. (2017). Sedimentology, 64, 311-358. [12] Turner 
S.M.R. et al. (2019). LPSC 50, abstract #1897. [13] Rampe, E.B., et 
al. (submitted). Mineralogy and Geochemistry of Sedimentary Rocks 
and Eolian Sediments in Gale Crater, Mars: A Review after Six 
Earth Years of Exploration with Curiosity. Submitted to Geochemis-
try. [14] Nachon M. et al. (2014). JGR: Planets, 119(9), 1991-2016.  
2481.pdf51st Lunar and Planetary Science Conference (2020)


Enhanced Groundwater Flow on and Below Vera Rubin Ridge, the Murray Formation, Gale Crater: Evidence from Thermochemical Modeling.

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsEnhanced groundwater flow on and below Vera Rubinridge, the Murray Formation, Gale Crater: Evidencefrom thermochemical modelingConference or Workshop ItemHow to cite:Turner, S.M.R.; Schwenzer, S.P.; Bridges, J.C.; Rampe, E.B.; Bedford, C.C.; Achilles, C.N.; McAdam, A.;Mangold, N.; Hicks, L.J.; Parnell, J.; Kirnbauer, T.; Fraeman, A.A. and Reed, M.H. (2020). Enhanced groundwaterflow on and below Vera Rubin ridge, the Murray Formation, Gale Crater: Evidence from thermochemical modeling.In: 51st Lunar and Planetary Science Conference, 16-20 Mar 2020 (Cancelled), Houston, USA.For guidance on citations see FAQs.c© [not recorded]Version: Accepted ManuscriptLink(s) to article on publisher’s website:https://www.hou.usra.edu/meetings/lpsc2020/pdf/2481.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukENHANCED GROUNDWATER FLOW ON AND BELOW VERA RUBIN RIDGE, THE MURRAY FORMATION, GALE CRATER: EVIDENCE FROM THERMOCHEMICAL MODELING.  S.M.R. Turner1, S.P. Schwenzer1, J.C. Bridges2, E.B. Rampe3, C.C. Bedford3,4,5, C.N. Achilles6, A. McAdam6, N. Mangold7, L.J. Hicks2, J. Parnell8, T. Kirnbauer9, A.A. Fraeman10, and M.H. Reed11. 1AstrobiologyOU, School of Environment, Earth and Ecosystem Sciences, The Open University, UK, (stuart.turner@open.ac.uk). 2Space Research Centre, School of Physics and Astronomy, University of Leicester, UK. 3NASA Johnson Space Center, USA. 4School of Physical Sciences, The Open University, UK. 5Lunar and Planetary Institute, USRA, USA. 6NASA Goddard Space Flight Center, USA. 7Laboratoire de Planétologie et Géodynamique, UMR6112 CNRS, Université de Nantes, Uni-versité Angers, France. 8School of Geosciences, University of Aberdeen, UK. 9TH Georg Agricola, Bochum, Ger-many. 10Jet Propulsion Laboratory, California Institute of Technology, USA. 11Department of Earth Sciences, Uni-versity of Oregon, USA.  Introduction:  NASA’s Mars Science Laboratory Curiosity rover has been exploring Vera Rubin ridge (VRR), part of the Murray formation in Gale crater, Mars, between sol 1809 and 2302. Evidence for Fe-oxides and phyllosilicates in mineralogical and geo-chemical data for this region was returned by Curiosity [1-5]. We applied thermochemical modeling to con-strain the formation conditions of the phyllosilicate-hematite assemblage identified on and below VRR. Average alteration compositions for the Murray for-mation on and below VRR were derived using CheMin and APXS data. These compositions were reacted with Gale Portage Water (GPW) between 25–100 °C and for 10% and 50% Fe3+/Fetot of the host rock [6]. Here we summarize models run at 50 °C and 10% Fe3+/Fetot for alteration compositions derived from Murray host rock compositions. Modeling:  CHIM-XPT is a program for compu-ting multicomponent heterogeneous chemical equilib-ria in aqueous-mineral-gas systems [7], and was previ-ously used in fluid-rock interaction studies for Gale crater [8-12]. Each step calculates equilibrium between a user-defined fluid and dissolved rock, meaning that each step can be interpreted independently. The wa-ter/rock ratio (W/R) in CHIM-XPT is the ratio of in-coming fluid to reacted rock. Here, the models focus on 1–100,000 W/R. The Starting Fluid. GPW was selected as the start-ing fluid, and has previously been used in thermo-chemical modeling studies [9,10,12]. GPW was de-rived from equilibrium mediation between a brine and rocks of the Gale area [9]. The solution is initially oxi-dizing (all S species as SO42-), and the redox in the fluid is controlled by the SO42-/HS- pair. The redox of the system throughout each model is dependent on the Fe3+/Fetot ratio of the host rock.  The Starting Rock. The composition of the altera-tion component in the Murray formation on and below VRR, along with an overall alteration composition, was derived by combining data returned by APXS and CheMin for the drill holes: Oudam (drilled on sol 1361), Marimba (sol 1422), Quela (sol 1464), Sebina (sol 1495), Stoer (sol 2136), Highfield (sol 2223), and Rock Hall (sol 2261) [13]. Using crystal chemistries derived for the magmatic minerals and mineral abun-dances determined using CheMin data, compositional oxide wt.% contributions from the magmatic phases were subtracted from the bulk APXS measurements. Ca-sulfate contributions were also excluded as these formed during late diagenesis [10,14]. Results: Thermochemical modeling was carried out for the temperature range 25–100 °C [6]. Here we compare model results for alteration compositions de-rived for VRR (Fig. 1) and below VRR (Fig. 2).  Figs. 1 and 2 show >10 wt.% hematite precipitating for ≥10,000 W/R for both alteration compositions at 50 °C and 10% Fe3+/Fetot.  Comparing summed clay mineral / hematite ratios (C/H) at 100, 1,000 and 10,000 W/R in the models in Figs. 1 and 2 with C/H from CheMin data suggests that the models at 10,000 W/R are comparable to Curiosity observations [6]. For 10% Fe3+/Fetot these C/H  values are 1.2 and 3.0 for on and below VRR, respectively. C/H values change to 1.2 and 1.7 for 50% Fe3+/Fetot. Comparable C/H values extracted from CheMin data are 1.9 ± 0.7 and 2.4 ± 0.3 for on and below VRR, re-spectively. When summing all Fe-oxides the value for VRR changes to 0.8 ± 0.3 due to akaganeite in Rock Hall.  Discussion: The models presented here and by [6] indicate potential formation conditions for the clay mineral-hematite assemblage in the Murray formation on and below VRR. To assess the comparability with previous modeling and Curiosity observations, the phyllosilicate chemical composition was summed for 10,000, 1,000 and 100 W/R models and shown on a ternary plot in Fig. 3. Fig. 3 shows the modeled phyllo-silicates at 10,000 W/R are close to Sheepbed unit model saponite [9], with the models trending towards nontronite compositions at 1,000 and 100 W/R [6]. Note that we assume the akaganeite and jarosite de-tected by CheMin in the Murray formation to be the result of later alteration where Fe was remobilized from the modeled mineral assemblages [6]. 2481.pdf51st Lunar and Planetary Science Conference (2020) Fig. 1: CHIM-XPT thermochemical model for the VRR Murray alteration composition reacted with GPW. The model was run at 50 °C and 0.1 Fe3+/Fetot.  Fig. 2: CHIM-XPT thermochemical model for the pre-VRR Murray alteration composition reacted with GPW. The model was run at 50 °C and 0.1 Fe3+/Fetot. Conclusions: Results presented here and by [6] show how derived alteration compositions for the Mur-ray formation can be reacted with a dilute brine (GPW) to produce an alteration mineral assemblage compara-ble with the clay mineral-hematite assemblage ob-served in the Murray formation on and below VRR. Results presented in this abstract focus on models run at 50 °C, however additional models show that tem-peratures can extend to 100 °C, with pH ranging be-tween 7.9 and 9.3 at ~10,000 W/R [6]. This modeling suggests that the alteration mineral assemblage ob-served in the Murray formation is due to enhanced groundwater flow through this part of the Gale sedi-mentary sequence, compared to previous observations and modeling in the Bradbury group at Yellowknife bay [9].  Fig. 3: Mg-Si+Al-Fetot at. ternary plot. Results at 10,000 (red), 1,000 (green) and 100 (blue) W/R from the thermochemical models in this abstract and in [6] are plotted with some additional data from other sources for comparison. CHIM-XPT results for the Sheepbed unit from [9] at 100 and 1,000 W/R are shown for comparison. References: [1] Rampe E.B. et al. (2017). EPSL, 471, 172-185. [2] Morrison S.M. et al. (2018). Am. Mineral. 103(6), 857-871. [3] Bristow T.F. et al. (2018). Science Advances (6), eaar3330. [4] Achilles C.N. et al. (submitted). Mineralogy of ancient fluvial-lacustrine sediments in Gale crater, Mars: Evidence for multiple diagenetic episodes. Submitted to JGR: Planets. [5] Rampe E.B. et al. (submitted). Mineralogy of Vera Rubin ridge from the Mars Sci-ence Laboratory CheMin instrument. Submitted to JGR: Planets. [6] Turner S.M.R. et al. (in prep). Fluid-Rock Reactions in the Murray Formation, including Vera Rubin ridge, Gale crater, Mars. To be submitted to JGR: Planets. [7] Reed M.H. et al. (2010). User Guide for CHIM-XPT: A Program for Computing Reaction Processes in Aqueous-Mineral-Gas Systems and MINTAB Guide. 71p., Universi-ty of Oregon, Eugene. [8] Bridges J.C. et al. (2015). LPSC 46, ab-stract #1769. [9] Bridges J.C. et al. (2015). JGR: Planets, 120, 1-19. [10] Schwenzer S.P. et al. (2016). MAPS, 51(11), 2175-2202. [11] Schieber J. et al. (2017). Sedimentology, 64, 311-358. [12] Turner S.M.R. et al. (2019). LPSC 50, abstract #1897. [13] Rampe, E.B., et al. (submitted). Mineralogy and Geochemistry of Sedimentary Rocks and Eolian Sediments in Gale Crater, Mars: A Review after Six Earth Years of Exploration with Curiosity. Submitted to Geochemis-try. [14] Nachon M. et al. (2014). JGR: Planets, 119(9), 1991-2016.  2481.pdf51st Lunar and Planetary Science Conference (2020)

Enhanced groundwater flow on and below Vera Rubin ridge, the Murray Formation, Gale Crater: Evidence from thermochemical modeling

Enhanced groundwater flow on and below Vera Rubin ridge, the Murray Formation, Gale Crater: Evidence from thermochemical modeling

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