Leinster Granite Research Articles

New light on the Oughterard Granite: Connemara's S-Type granite, Ireland

Abstract: Most of the Connemara granites, including the Galway Granite batholith, have a clearly defined circular or ellipsoidal outcrop shape and are I-Type granites often with K-feldspar phenocrysts, whereas the Oughterard Granite (OG) forms numerous small intrusions scattered east-west over 40km with two larger linked bodies near Oughterard and is S-Type and aphyric. The only comprehensive mapping, mineralogical and chemical study of the OG was published over 50 years ago before the important 1974 recognition of the distinction of I- and S-Type granites was first made. New mapping of the southern Oughterard area with small OG intrusions is presented and many scattered published chemical and Rb, Sr, S and Pb isotopic studies integrated to confirm overall their individual conclusions that the peraluminous OG is of S-Type, being formed from melted Dalradian rocks as are the fluid-carried associated uneconomic mineral deposits. The OG is confined to the high sillimanite zone, mostly south of, and mainly later than, the 465-464Ma D4 Connemara Antiform, where a wide (>15km N-S) >70km E-W band of 469Ma gabbros and 467Ma quartz diorite gneisses intruded into already hot Dalradian rocks undergoing regional metamorphism. This generated the OG magmas by partial melting of pelites and semi-pelites. The upward intrusion of the OG magma was significantly delayed, as has been shown by precise dating in other granites elsewhere, to ∼464-461Ma during the late stages and mostly after D4 but before the country rocks had completely cooled. The OG intrusions as a whole probably form the second largest area of S-Type granite in Ireland, after the Leinster Granite.

New Light on the Oughterard Granite: Connemara’s S-Type Granite, Ireland

Most of the Connemara granites, including the Galway Granite batholith, have a clearly defined circular or ellipsoidal outcrop shape and are I-Type granites often with K-feldspar phenocrysts, whereas the Oughterard Granite (OG) forms numerous small intrusions scattered east-west over 40km with two larger linked bodies near Oughterard and is S-Type and aphyric. The only comprehensive mapping, mineralogical and chemical study of the OG was published over 50 years ago before the important 1974 recognition of the distinction of I- and S-Type granites was first made. New mapping of the southern Oughterard area with small OG intrusions is presented and many scattered published chemical and Rb, Sr, S and Pb isotopic studies integrated to confirm overall their individual conclusions that the peraluminous OG is of S-Type, being formed from melted Dalradian rocks as are the fluid-carried associated uneconomic mineral deposits. The OG is confined to the high sillimanite zone, mostly south of, and mainly later than, the 465-464Ma D4 Connemara Antiform, where a wide (>15km N-S) >70km E-W band of 469Ma gabbros and 467Ma quartz diorite gneisses intruded into already hot Dalradian rocks undergoing regional metamorphism. This generated the OG magmas by partial melting of pelites and semi-pelites. The upward intrusion of the OG magma was significantly delayed, as has been shown by precise dating in other granites elsewhere, to ~464-461Ma during the late stages and mostly after D4 but before the country rocks had completely cooled. The OG intrusions as a whole probably form the second largest area of S-Type granite in Ireland, after the Leinster Granite.

Detailed Geogenic Radon Potential Mapping Using Geospatial Analysis of Multiple Geo-Variables—A Case Study from a High-Risk Area in SE Ireland

A detailed investigation of geogenic radon potential (GRP) was carried out near Graiguenamanagh town (County Kilkenny, Ireland) by performing a spatial regression analysis on radon-related variables to evaluate the exposure of people to natural radiation (i.e., radon, thoron and gamma radiation). The study area includes an offshoot of the Caledonian Leinster Granite, which is locally intruded into Ordovician metasediments. To model radon release potential at different points, an ordinary least squared (OLS) regression model was developed in which soil gas radon (SGR) concentrations were considered as the response value. Proxy variables such as radionuclide concentrations obtained from airborne radiometric surveys, soil gas permeability, distance from major faults and a digital terrain model were used as the input predictors. ArcGIS and QGIS software together with XLSTAT statistical software were used to visualise, analyse and validate the data and models. The proposed GRP models were validated through diagnostic tests. Empirical Bayesian kriging (EBK) was used to produce the map of the spatial distribution of predicted GRP values and to estimate the prediction uncertainty. The methodology described here can be extended for larger areas and the models could be utilised to estimate the GRPs of other areas where radon-related proxy values are available.

Uranium in groundwaters: Insights from the Leinster granite, SE Ireland

Uranium concentrations in groundwaters from >100 private wells in the Caledonian Leinster Granite Batholith of SE Ireland range from a few μg/l to >300 μg/l. Approximately 10% of the wells exhibit uranium concentrations that exceed the current WHO provisional guideline of 30 μg/l and a further 10% exceed the original WHO guideline value of 15 μg/l. New whole-rock geochemical analyses and laboratory batch leaching experiments confirm the granite as the ultimate source of the groundwater uranium, but carbonate-bearing glacial deposits that overlie the granite play an important role in facilitating the generation of soluble and mobile anionic uranyl carbonate complexes. Whilst the granite has average uranium concentrations broadly similar to other Irish and British Caledonian granites, it is enriched locally in uranium, with whole-rock values up to c. 30 mg/kg. Uraniferous zircon, apatite, monazite and associations with secondary Fe-bearing oxide minerals were detected in drillcore whole-rock samples that had the highest uranium concentrations, but uraninite was not detected. Broad positive correlations between groundwater uranium concentrations and bicarbonate alkalinity and electrical conductivity are found in both the sampled groundwaters and in laboratory leachates of the granite and surficial glacial deposits. Leachates from the granite had approximately an order of magnitude higher uranium concentrations compared with those from the overlying limestone-bearing glacial tills. (234U/238U) ratios for the groundwaters and the leachates always exceed unity, indicating preferential leaching of loosely bound radiogenic 234U from mineral surfaces or grain boundaries into the groundwaters, rather than wholescale dissolution of the primary uraniferous minerals in the granite. Strontium isotopes ratios in the groundwaters constrain the balance between limestone and granite-derived Sr, and by extension the sources of dissolved Ca. These data indicate that calcite dissolution is the main source of dissolved calcium, highlighting the role of weathering of overlying limestone-bearing glacial tills during recharge in determining the geochemistry of the groundwaters. Geochemical modelling indicates that in the oxidising groundwaters of the study area U6+ is dominant, in the form of UO2(CO3)3−4 at the high pH values (7.49–7.69) of waters from wells overlain by limestone-bearing till. By contrast, in a small number of wells overlain by granite-bearing till, modelling indicates that the dominant species is UO2(CO3)2−2 reflecting their lower pH (6.22–6.30). Overall, carbonate species play a major role in uranium solubility and mobility in these granite-hosted groundwaters.

Using Tellus stream sediment geochemistry to fingerprint regional geology and mineralisation systems in Southeast Ireland

Regional stream sediment geochemistry provides a useful tool for screening relatively large areas for anomalous metal concentrations. Large, open-source governmental datasets represent an affordable option for smaller companies to prioritise areas for follow-up. Equally, such datasets are useful in applied geochemical research. This study investigates recently released Tellus regional stream sediment analyses for Southeast Ireland, focusing on counties Wicklow, Wexford, and parts of Kildare, Carlow, Kilkenny and Waterford. The aim is to: i) apply trace element ratios and vectors to define and confirm key lithologies and types of mineralisation previously mapped in the study area, ii) provide a tool to reconstruct the geological setting at a 1:500k regional scale and iii) outline follow-up areas from a mineral exploration point of view. I demonstrate that governmental geochemical datasets can not only define anomalous areas per se, but also support the recognition of regional geological trends and the definition of a number of ore deposit styles. The Tellus dataset for Southeast Ireland, despite its low-density and regional nature, confirmed the regional geological setting albeit in limited detail. Geochemical vectors for Li-Cs-Ta (LCT) pegmatites in the Leinster Granite as well as Volcanogenic Massive Sulphide (VMS) mineralisation in the Copper Coast and Avoca areas, were established and support previous univariate anomaly detection studies. The workflow will be particularly beneficial in remote and poorly mapped areas where geochemical surveys can add additional value to support ongoing definition of stratigraphy, lithologies and anomalous metal abundances.

The Origin of Spodumene Pegmatites Associated With the Leinster Granite In Southeast Ireland

Abstract Rare-element pegmatites have diverse chemical signatures and are important sources of strategic metals such as Li, Cs, and Ta. The two main hypotheses to explain rare-element pegmatite formation are (1) residual magmas from the crystallization of granitic rocks, and (2) partial melts from a relatively rare-element-rich source. In southeast Ireland, spodumene and spodumene-free pegmatite dikes occur along the eastern margin of the S-type Leinster Granite batholith. With indistinguishable emplacement ages around 400 Ma, the origin of the Li-rich pegmatitic fluids has been suggested to have resulted from extreme fractional crystallization of Leinster Granite granodiorite magma. To test this hypothesis, we used whole-rock geochemistry of pegmatite and granodiorite samples from drill cores and geochemical modeling of in situ crystallization and batch melting to investigate which process better explains the formation of the pegmatites. Chemical signatures of the pegmatites and granodiorite do not indicate a direct comagmatic relationship, as the granodiorite has higher concentrations of many incompatible elements than the pegmatites ( e.g ., concentrations of Zr, Ti, and Y). Concentrations of Li, Rb, Cs, Sr, and Ba show no clear fractionation trends from granodiorite to pegmatite. The in situ crystallization model using the average granodiorite composition as the initial magma generates a range of compositions that does not include pegmatites, so it is unlikely that they represent residual granitic magmas. Modeling of partial melting indicates that the Leinster Granite granodiorite and pegmatite magmas could have formed in separate events and from chemically different source rocks, with the pegmatite magmas presumably formed in a younger event because the pegmatites intrude the granodiorite.

Understanding the origin of rare element pegmatites associated with the Leinster Granite in southeast Ireland

Rare element pegmatites are important sources of strategic metals such as Li–Cs–Ta and are represented by a large diversity of chemical signatures. The mechanisms to form such unusual rocks are sti...

Complex weathering effects on durability characteristics of building stone

Abstract Durability characteristics of five stone types are assessed and compared using the standardized sodium sulphate salt crystallization test and a modified laboratory weathering simulation in which a combination of salt weathering (Na 2 SO 4 ) and freeze-thaw cycles are used. Data indicate significant differences in durability rankings between the two test methods especially in lower-order durability stone types. Both the standard salt crystallization test and the modified durability test identify Leinster Granite and Stanton Moor B Sandstone as the most durable of the five stone types, with the granite performing well under both sets of conditions. Discrepancy between rankings arises in the lower orders, with Portland Limestone, Stanton Moor A Sandstone and especially Dumfries Sandstone responding differently to the two sets of experimental conditions. In the modified durability test the range of permeability values for each stone type produced the same ranking as that indicated by mean percentage weight change values but mean permeability values for each stone type do not appear to be reliable predictors of weathering response. Differences in durability rankings between the two test regimes are attributed in the first instance to the temperature conditions used, with more extreme and unrealistic heating to 103 °C in the standardized test ‘over-weathering’ stone while conditions in the modified test allowed the development of stone-specific decay characteristics. Inclusion of salt weathering and freeze-thaw cycles in the modified test introduced complexity into the decay process that more accurately reflects ‘real-world’ conditions. Data also indicate that relatively minor structural and mineralogical differences between samples of the same stone type can significantly influence weathering behaviour, resulting in distinct rates and patterns of breakdown.

Manganese Oxide Minerals from Veins in the Leinster Granite

Hollandite and cryptomelane occur as intergrown botryoidal masses with goethite in a quartz vein hosted by the Leinster Granite at Cloghleagh Mine, near Blessington, Co. Wicklow. Coronadite and romanA¨chite accompany pyromorphite in an oxidised Pb–Zni?½quartz vein at Old Luganure Mine, Glendasan, also in the Leinster Granite. Quantitative analyses show the Cloghleagh material to consist of bands of varying K:Ba ratio ranging from cryptomelane (K > Ba) to hollandite (Ba > K), but neither approaches end member composition. The Luganure material is mostly coronadite of near Pb-end member composition, in some cases mixed, or intergrown with, romanA¨chite.

Manganese Oxide Minerals from Veins in the Leinster Granite

Hollandite and cryptomelane occur as intergrown botryoidal masses with goethite in a quartz vein hosted by the Leinster Granite at Cloghleagh Mine, near Blessington, Co. Wicklow. Coronadite and romanèchite accompany pyromorphite in an oxidised Pb-Zn-quartz vein at Old Luganure Mine, Glendasan, also in the Leinster Granite. Quantitative analyses show the Cloghleagh material to consist of bands of varying K:Ba ratio ranging from cryptomelane (K > Ba) to hollandite (Ba > K), but neither approaches end member composition. The Luganure material is mostly coronadite of near Pb-end member composition, in some cases mixed, or intergrown with, romanèchite.

A review of the Irish crustal structure and signatures from the Caledonian and Variscan Orogenies

AbstractThis paper reviews the complex crustal and upper‐mantle seismic velocity structure of Ireland and surrounding seas. Data from 11 seismic refraction profiles reveal that onshore Ireland mean crustal velocities range between 6.25 and 6.5 km s−1 with crustal thickness of 28.5–32 km. Superimposed on a three‐layer crust, the sedimentary layer has a thickness of approximately 6–8 km at the southern coastline, but only 3–4 km in the vicinity of the Shannon Estuary in western Ireland. The lateral heterogeneity of the upper‐crustal layer is pervasive throughout Ireland, with velocities of 5.7–6.2 km s−1 and a layer thickness of 3–10 km. A low‐velocity zone is found in the south‐east which is interpreted as the buried south‐western extension of the Leinster Granite. The mid‐crustal layer (6.3–6.7 km s−1) is between 8 and 16 km thick. Significant changes occur in the vicinity of the Shannon Estuary, around the location of the Iapetus Suture Zone. The lower crust is fairly uniform with velocities of 6.8–7.2 km s−1 and a thickness of approximately 8–10 km except towards the south of Ireland where the Moho appears as a transition zone. Offshore Ireland, a two‐layer crust with a thickness of 24–26 km beneath the North Celtic Sea Basin and only 14–15 km beneath the Rockall Trough prevails.

Evidence for Cenozoic tectonic deformation in SE Ireland and near offshore

An integrated study of topography, bathymetry, high‐resolution aeromagnetic data, and structural observations demonstrates significant Cenozoic fault activity in SE Ireland. Tectonically generated knickpoints and reddened fault breccias along topographic escarpments that are underlain by greywacke bedrock and trend oblique to the regional Caledonian strike provide evidence for fault displacement. Near‐offshore faults with similar geometry produce present‐day bathymetric scarps and localized tectonic topography in the inverted Kish Bank Basin. The integration of offshore high resolution aeromagnetic data and structural interpretation of the Kish Bank Basin provides evidence for dextral transtension on NNW trending faults and sinistral transpression on ENE trending faults bounding a lower Paleozoic to Carboniferous basement block. These faults correlate onshore with previously recognized Caledonian faults producing topographic offsets and surface uplift. To the north, offshore structures can be traced onshore and cut exposures of the Caledonian Leinster Granite. Structural analysis of these outcrops indicates post‐Variscan deformation. A major fault on the NW margin of the batholith cuts a major erosion surface developed on Carboniferous carbonate rocks, and nonmarine Miocene deposits are preserved above this surface. Fault kinematics provide evidence of two paleostress systems: (1) NW‐SE σ1, subvertical σ2 and NE‐SW σ3 followed by (2) a clockwise swing of σ1 to NNW‐SSE. Timing of deformation in both stress systems is probably post‐Oligocene age. The mechanism driving this deformation is likely ridge‐push. Much is already known about Cenozoic tectonics and exhumation from offshore basins. This study shows that onshore Ireland has also been affected by significant tectonic activity and exhumation during the Cenozoic.

VARNET-96: three-dimensional upper crustal velocity structure of SW Ireland

During the VARNET-96 seismic experiment three seismic refraction/wide-angle reflection profiles were acquired in order to examine the crustal structure in the southwest of Ireland. A total of 170 seismic stations were used on 300 recording sites. The shotpoint geometry was designed to allow for inline and offline fan shot recordings on the three profiles, using a total of 34 shots. Results from 3-D ray-trace and inversion modelling illustrate the pervasive lateral heterogeneity of the crust south of the Shannon Estuary. About 5 km of interpreted Palaeozoic sediment at the south coast was associated with the sedimentary infill of the Munster and South Munster Basins. This sedimentary layer, which thins to approximately 2 km in the northern Munster Basin, is significantly thinner than previously estimated from geological field studies. High-velocity zones beneath Dingle Bay and the Kenmare River region may be associated with the deep traces of the Killarney-Mallow Fault Zone and the Cork-Kenmare line. A zone of high-velocity upper crust (6.4-6.6 km s - 1 ) beneath the South Munster Basin is found in the area between the Kenmare-Killarney and the Leinster Granite gravity lows. The depth to the Moho varies from approximately 28-29 km at the south coast to approximately 32-33 km in the Dingle-Shannon Basin. The interpretation of the 2-D and 3-D velocity models suggests that Variscan deformation is confined to sedimentary and upper crustal structures in the southwest of Ireland.

Disequilibrium textures in the Leinster Granite Complex, SE Ireland: evidence for acid-acid magma mixing

AbstractThe LGC (Leinster Granite Complex) in SE Ireland consists of five plutons or Units. Units 1 and 3 display complex magmatic disequilibrium textures described here for the first time. The textures indicative of disequilibrium include boxy cellular plagioclase, oscillatory zoning, calcic spike zones and combinations of these within individual plagioclase feldspar crystals. The textures are interpreted as having formed in a dynamic magmatic environment which facilitated acid-acid mixing on a variety of scales and at a variety of stages between source to emplacement. It is proposed that the restricted distribution of disequilibrium textures was a result of the complex strain regime operating within the crust during assembly of Units 1 and 3.

Ordovician and Silurian acritarch assemblages from the west Leinster and Slievenamon areas of southeast Ireland

The Lower Palaeozoic sequences west of the Leinster Granite and in the Slievenamon Inlier of southeast Ireland have been palynologically re-investigated. Most of the productive samples yielded sufficient identifiable acritarchs for positive stratigraphical age determinations for several of the formations. The samples also include rare cryptospores, scolecodonts and tubular structures. Previous work in the area west of the Leinster Granite proposed an unbroken succession from Early Ordovician Ribband Group turbidites and volcanics passing up conformably to Early Ordovician to Late Silurian Kilcullen Group. The new palynological data clearly show that the Kilcullen Group in this area is entirely Silurian (Llandovery–early Wenlock) in age, also results obtained from the same group at Slievenamon confirm the previously reported Silurian age. Ordovician acritarchs found in the Kilcullen Group of both study areas are reworked and range in age from late Tremadoc to Llanvirn. The new data reveal a major stratigraphic break between the Ribband Group dated as Early and Middle Ordovician and the Silurian Kilcullen Group. This major break extends some hundreds of kms southwest to the Dingle Peninsula and possibly equates with a similar discontinuity in the Isle of Man to the northeast. This break would thus appear to be a major feature within the northwestern Avalonian margin sequence.

Fluid migration and rock interactions during dolomitisation of the Dinantian Irish Midlands and Dublin Basin

Lower Carboniferous carbonate rocks of the southern Irish Midlands and the Dublin Basin record a complex history of dolomitisation involving multiple fluid sources. At least one regional migration of fluid in both the south Midlands and the Dublin Basin is interpreted based on regional dolomite cement correlation in units as young as Asbian (Supra-Waulsortian). This cement paragenetically predates most main-stage Zn–Pb mineralisation. O isotope and fluid inclusion data appear to reflect stratigraphic and geographic controls on fluid type. δ18O values for the Sub-Waulsortian are the most negative (−10PDB) in the Dublin Basin. Waulsortian δ18O values are also most negative (−10PDB) in the Dublin Basin and in the south Midlands, near the Rathdowney Trend. The δ18O values for the Supra-Waulsortian are the most negative (−10PDB) from the Rathdowney Trend southeast towards the Leinster granite. If the patterns of the increasing δ18O values reflect cooling along their respective flow paths, then the distinct patterns noted in each stratigraphic interval require multiple fluids from multiple sources. In contrast, a single fluid and source affecting the entire stratigraphic section should yield a similar pattern throughout. Analysis of fluid inclusion data also suggests that three, chemically and thermally, distinct fluids precipitated dolomite, and those fluids in the Supra-Waulsortian are at slightly higher temperature and are less saline than their counterparts in the Waulsortian and Sub-Waulsortian. The patterns of the δ18O values could reflect other processes besides cooling, such as differences in fluid–rock interaction, or introduction of multiple chemically distinct fluids at different times and loci throughout the diagenetic hydrothermal history. Stable isotopes alone cannot definitively answer questions regarding the localised versus regional flow, or distinguish fluid sources from water–rock reactions. However, using these isotopes and other geochemical data we propose a hybrid model of fluid flow, incorporating both regional as well as localised fluid flow, occurring during the dolomitisation of the Dinantian rocks of Ireland.

New palynological data from the Leinster Lower Palaeozoic massif, southeastern Ireland

ABSTRACTIn southeastern Ireland, the tectonic evolution of the northwestern Avalonian margin is rather poorly understood and only partially constrained. This is because the stratigraphy comprises in the main unfossiliferous turbidites. Nevertheless, some authors have attempted to define ‘terranes’ and ‘tracts’ in the region, aided by several significant Caledonoid-trending structural breaks that can be determined in the field. Palynological work was carried out in the early 1970s and established a range of ages from approximately mid Cambrian to late Silurian, although much of the succession proved barren. In the current study, the Lower Palaeozoic sequences W of the Leinster Granite and in the Slievenamon Inlier to the S have been palynologically re-investigated. Previous work proposed an unbroken succession from lower Ordovician Ribband Group turbidites and volcanics younging westwards conformably into upper Silurian Kilcullen Group sediments. The new study clearly shows that the Ordovician palynomorphs in the older part of the Kilcullen Group are reworked. In fact, there exists a major stratigraphical break between the Ribband Group dated as early Ordovician, Arenig, and the Kilcullen Group which is entirely Silurian, late Llandovery to early Wenlock in age. This major break has a minimum strike length of 150 km and is most likely much longer, extending some hundreds of kilometres SW to Dingle and possibly equating with a similar discontinuity in the Isle of Man to the NE. This break would thus appear to be a major feature within the succession of the northwestern Avalonian margin.

Fluid inclusion study of the Ballinglen W-Sn-sulphide mineralization, SE Ireland

Scheelite-mineralized microtonalite sheets occur on the SE margin of the end-Caledonian Leinster Granite in SE Ireland. Scheelite, polymetallic sulphides and minor cassiterite occur in veins in the microtonalites, disseminated throughout the greisened microtonalite sheets and in the adjacent wallrocks. Two major mineralized vein types occur in the microtonalite sheets: (1) Scheelite ± arsenopyrite ± pyrrhotite occur in quartz-fluorite veins, generally without a muscovite selvage; (2) Sphalerite ± chalcopyrite ± pyrite ± galena ± cassiterite ± stannite occur in quartz + fluorite veins with a coarse muscovite selvage and are often intergrown with the muscovite. Quartz-hosted fluid inclusions were examined from representative samples of both vein types using petrographic, microthermometric and laser Raman spectroscopic techniques. Three distinct types of fluid inclusions have been recognized. Primary, vapour rich Type 1 inclusions in quartz from the scheelite-mineralized veins are of H2O-CO2-CH4-N2 ± H2S ± NaCl composition and formed between 360–530 °C. Primary and secondary, liquid-rich Type 2 fluid inclusions in the base metal sulphide-mineralized veins are of H2O-CH4-N2 ± H2S-NaCl composition and formed between 340–480 °C. They also occur as pseudosecondary and secondary inclusions in scheelite-mineralized veins. Late dilute, low temperature H2O-NaCl + KCl fluid inclusions may be related to late-Caledonian convection of meteoric waters around the cooling Leinster Granite batholith.

Laboruntersuchungen zur Wechselwirkung zwischen Mauer· und Ausfugemörtel und den Mauersteinen / Laboratory Studies of the Interaction between Bedding and Pointing Mortars and Building Stones

Abstract The physical and chemical properties of bedding and pointing mortars have a major influence on the nature, rate and extent of decay of pointed stonework. Specially designed mortars can prevent physical damage and greatly reduce chemical and biological decay in both the mortars themselves and the adjacent stones. This study describes the physical and chemico-mineralogical changes that occur in a number of different stone-mortar combinations. Three types of mortar were designed and fabricated in the laboratory in accordance with [1,2]. These were examined in combination with Leinster granite, Portland limestone and Baumberger sandstone by exposing standard samples comprised of two pieces of stone 5 cm χ 5 cm χ 5 cm separated by a 5 mm mortar filled joint to artificial ageing tests in a chamber. Thin sections were examined to determine what changes had taken place in the stone and the mortar. The physical properties of the stones and mortars were determined separately. The lime mortar, though chemically well matched with the limestone and sandstone, proved to be unsuitable because of loss of cohesion. The resultant microcracking, detected by pétrographie microscope, appeared to be caused by shrinkage during drying rather than by carbonation or cycling-alteration processes. Granite-lime mortar combinations showed low adherence and decreased durability of the mortar. This effect may be the result of the greatly differing physical properties of the lime mix and granite. The ageing tests revealed a high durability in the cement mixes. The study demonstrated the suitability of cement content mortars with poorly sorted aggregate and plasticiser for bedding and pointing in granite stonework. They also illustrated the need for care with the design of lime mortar mixes to ensure adequate binder-aggregate adhesion.

Weathering of Leinster granite under ambient atmospheric conditions

The weathering of Leinster granite under ambient atmospheric conditions has been studied. Specially constructed sampling devices, called ‘micro-catchment units’, were installed to sample runoff water. The chemical composition of the runoff water, as well as of individual particles in the runoff, has been determined and interpreted. In addition, the stone material itself was studied by micro-analysis after 3 years of sheltered and unsheltered exposure. Very little material loss was noted, but some structural changes were observed after unsheltered exposure.