The Maqarin Natural Analogue

Home , Afwillite, Apophyllite, Jennite, Spurrite, Thaumasite, Tobermorite

A E Milodowski

. British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, United Kingdom

Royal Society of Chemistry: Chemistry of Geological Disposal University of Manchester, 2nd December 2009

© NERC All rights reserved Contents 1. Introduction • Conceptual model of the alkaline disturbed zone (ADZ) • Why study natural analogue systems? 2. Background to the Maqarin Natural Analogue Project 3. Geological setting • Location of the Maqarin site and study areas • Origin of the hyperalkaline spring phenomenon 4. Groundwater chemistry 5. Mineralogical and petrological investigations • The primary metamorphic rock [“Cement Zone”] source • Interactions of the hyperalkaline plume [the “Alkali Disturbed Zone”] • Impacts on hydrogeological properties 6. Summary and conclusions

pH ‘early’ HPF concentration time/distance

Stage I Stage II Stage III 14 OPC: 100 cycles Low pH cement: 13 100 cycles

11 Na/K OH Ca(OH)2 10 leaching buffering pH 9

8 C-S-H 7 buffering 6 1 10 100 1000 Cycles of pore water exchange

• In low permeability rocks, duration of a “cycle” may be in the order of thousands of years

• Extensive use of cementitious materials is standard in many waste repositories, ranging from tunnel liners to grouts to the waste itself

• Cement porewaters initially have pH of 13.3, host rock groundwaters have pH of 7 to 10.....DISEQUILIBRIUM

• Assuming an appropriate host rock, cementitious porewaters could be leaching out into the host rock for 104 to 106 years

• Assuming the disequilibrium noted above, this means that the host rock conditions around a cementitious repository will be chemically disturbed - what are the PA implications?

• Some likely implications include:

• Interaction of the cementitious leachates with the host rock will alter the rock mineralogy • Cement colloids produced in and around the interaction zone could migrate through the host rock • Sorption in the host rock will be altered (better or worse?)

URL NA System Understanding

Conceptual Models

Field Lab Tests PA - Models Confidence studies

• Phase I 1989-1991 • funded by Nirex, Nagra, Ontario Hydro Alexander (ed.), 1992, Nagra Technical Report 91-10 • Phase II 1992-1994 • funded by Nirex, Nagra, SKB Linklater (ed.), 1998, Nirex Science Report S/98/003 • Phase III 1993-1996 • funded by Nirex, Nagra, SKB, UK Environment Agency Smellie (ed.), 1998, SKB Technical Report TR-98-04 • Phase IV 1999-2005 • Funded by Nirex, Nagra, SKB, ANDRA, CEA, JAEA Various reports

Yarmouk Tertiary Basalt Adit 6 Bridge site

Tert.-Cret. Maqarin Stn. chalks, clay biomicrites Western Springs

Wadi Sijin

Western Springs Eastern Springs

Syrian [Hauran] Basalt Pleistocene

O2 O2 Chalky Limestone Fm. Quaternary fluvial Lower Tertiary gravels and colluvium

combustion Bituminous Limestone Fm. calcination R. Yarmouk Upper Cretaceous

organic-rich, cherty, phosphatic, limestones and clay biomicrites with up to 20% organic C

Ca-HCO3 groundwater percolates the marble

Alteration (hydration) of marble Marble R. Yarmouk (larnite, spurrite, lime) and leaching of secondary portlandite, CSH minerals

Hyperalkaline [pH >12.5] Ca-OH-SO4 groundwater reacts with host rocks

A Natural Analogue for the long-term evolution of an alkaline leachate plume leaching from cementitious L/ILW radioactive waste repository

Adit 6 (Unity Dam) Maqarin Station cutting

Constructed in 1979 - photo 1990 Constructed in c.1905 - photo 1990

Yarmouk River: south bank

Hyperalkaline springs discharge through Quaternary basalt-chert-limestone boulder gravels

Eastern Springs Western Springs • pH 12.3-12.5 12.5-12.7 • Ca 740-900 mg/l ~1060 mg/l • K 9-17.5 mg/l ~350 mg/l • OH 430-640 mg/l 630-650 mg/l • SO4 200-300 mg/l ~1510 mg/l

• Se 100-300 µg/l ~1070 µg/l • Cr 0.5-1.5 mg/l ~5.08 mg/l* • Re ~1 µg/l 5.8 µg/l

*Imparts yellow (chromate) colour to waters in the Western Springs

•pH>12.5 •Two distinct groups

Eastern Springs

0100% Western Springs 100 0% - 2 M 3 SO O g 2 C 4 2 + - + + + + - K N 3 C O l - a + C H

100% 0% 0 100% 0 OH- 100% 100% Ca2+ 0%

•Metamorphosed phosphatic limestone - ellestadite-rich marbles

•Metamorphosed cherty limestone -larnite,spurrite, wollastonite-rich marbles

•Metamorphosed argillaceous limestones -brownmillerite, calcsilicates, calcaluminates spurrite, chrome-ferrite phases, brucite, periclase, portlandite, lime.

Tobermorite CSH gels ettringite

ettringite thaumasite

thaumasite ettringite apophyllite afwillte

Ternary Ca-Al-Si mol% element plot of hydrated cement phases: microprobe data from Adit 6, phase IV Si GRID AXES Ettringite-thaumasite Tobermorite CSH Afwillite Ideal formulae Tacharanite

Tobermorite

Afw illite

Thaumasite

Al Ettringite Ca

Oldhamite CaS

Cu-K-S-Se

•0.3-3.3 % K2O present in primary spurrite- like calcium silicate-sulphate phase

•Minor P also present in all primary thaumasite calcsilicates

•K-rich ‘spurrite-like’ phase readily alters to thaumasite

•K-free spurrite alters more slowly

secondary thaumasite alteration Se S

Electron microprobe X-ray elemental maps of altered K-rich calcium silicate

- - Ingress of Ca- HCO3 HCO3 water moves into marbles. Calcite ± aragonite 1 groundwater in marble Dissolution of Ca and K-bearing Barite

(‘cement zone’) sulphides and selenides and Baritocelestite (Sr,Ca)SO4 available lime Hashemite Ba(CrO4 ,SO4)

Initial hydration of ‘cement Alteration of most reactive Tobermorite, CSH gels 2 zone’ calcium silicates (larnite, lime and K-bearing ‘spurrite’)

Hydration of calcium silico- Alteration of less reactive Afwillite, CSH gels 3 sulphates calcium slicates and silico- Ettringite-thaumasite phosphates (spurrite, ellestadite) Apophyllite

Calcite, gypsum, silica gel 4 Interaction with bicarbonate groundwater

Interaction with surface Atmospheric CO decomposes Calcite, gypsum, silica gel 5 2 atmosphere (dry periods + thaumasite on adit walls or post adit draining) and exposed in dry fractures

•CSH(I) formed by reaction with quartz (chert concretion)

•Where CSH minerals are in sealed fractures, they tend to remain unaltered

•Reaction with kaolinite, illite, quartz, carbonate minerals •Reaction products dominated by CSH gels, tobermorite and jennite- thaumasite-ettringite vein mineralisation

•Secondary CSH phases altered by SO4 groundwaters •Complex oscillations of CSH minerals and sulphate minerals

Si 100 %

zeolite crystalline phases gels

tobermorite‐like gels

jennite‐like gels zeolitic gels jennite

100 % 100 % Al Ca Summary compositions (molar ratios) of crystalline and non-crystalline CSH and CASH alteration products, determined by EPMA and ATEM.

calcite/ aragonite

ettringite/thaumasite

gypsum

tobermorite/CSH(I) gel

jennite/CSH(II) gel

zeolite/zeolite gel

smectite

TIME

Uranium fission track registration studies

U is remobilised when CSH mineral are altered by sulphate

Early stages of “ADZ” interaction: •Dissolution of silicate (silica, quartz, kaolinite) and carbonate minerals in the adjacent wallrock •Locallised enhanced porosity

Reaction with hyperalkaline groundwater-rock Ett interaction tends to seal fractures in the natural “ADZ”

CSH minerals appear to have existed for around 80- 100 Ka

© NERC All rights reserved Conclusions 1. Good natural analogue for understanding the evolution of the ADZ – evolution of the Maqarin groundwater system mimics the evolution of OPC cement porewaters and conceptual model of alkali plume development. 2. ADZ alteration dominated by CSH reaction products 3. Zeolites predicted by models but natural system dominated by aluminous CSH gels (Al incorporated into CSH, rather than zeolite) 4. Reaction products similar regardless of host rock lithology (basalt, chert, clay-bearing carbonate rocks) 5. ADZ reactions tend to lead to fracture sealing, although in wallrock porosity may be enhanced initially. 6. Sulphatic alteration of CSH may lead to secondary re-release of some uptaken species (e.g. U). 7. Plume seen to extend to ~500 m from cement source

Russell Alexander, Bedrock Geosciences,Switzerland John Smellie, Conterra AB, Sweden Urs Maeder, University of Berne Paul Degnan, (Nirex) Hani Khoury, University of Jordan, Amman Elias Salameh, Univerersity of Jordan, Amman Laurent Trotignon, CEA

BGS Ewan Hylsop Simon Chenery Julie West, Chris Rochelle Jonathan Pearce