Figures, photographs and tables

Figures

(Figure 1) Outline map of major geological provinces in Scotland, and the distribution of Caledonian igneous complexes ('granites'); with location of the Ballachulish area.

(Figure 2) Outline of lithostratigraphic units and major regional structures around the Ballachulish Igneous Complex. The position of the garnet isograd of regional metamorphism. Which formed prior to intrusion of the complex, is extrapolated across the area of the complex. From Pattison & Harte (1997).

(Figure 3) Geological cross-sections through the igneous complex (see section lines on Coloured Map (Map 1) and (Figure 7)), from Weiss (1986) and Troll and Weiss (1991). 1 - metasediments. Lined patient indicates pelites and semipelites; lined pattern with dots represents quartzites. Squiggly lines indicate migmatitic rocks. The orientation of the lines gives the attitude of the bedding projected into the cross section. 2 - monzodiorites, showing flow- and deformation foliation. 3 - quartz diorites, showing alignment of metasedimentaty xenoliths. 4 - fine grained diorites with xenoliths. 5 - granites. The flue crossed ornament in the centre represents leucogranite, and the bounding stippled margin represents a gradational contact with the main granite. 6 - hybrid transition zones between granite and quartz diorite. The dotted line labelled '..Sgorr Dhearg' represents the projected topographic expression of this peak which occurs about 300 m N of the line of section.

(Figure 4) Pressure-temperature grid of reactions in the chemical system K₂O-FeO-MgO-Al₂O₃-SiO₂-H₂O for typical mineral compositions in quartz-bearing pelitic rocks from Ballachulish (Pattison Harte, 1997). Dehydration reactions below the initial melting reaction (Pl+Kfs+Qtz+H₂O = L) are shown in solid lines. Higher grade reactions up-temperature of the initial melting reaction are shown in dashed lines. Als = andalusite or sillimanite. V = hydrous vapour, The short dashed line numbered 3 is the metastable extension of Ms+Qtz = Als+Kfs+V The dot-dashed reaction 5, Ms=Crn+Kfs+V, only occurs in quartz-absent rocks. The And=Sil curve is from Pattison (1992). H - And=Sil curve and triple point of Holdaway (1971); RGB - And=Sil curve and triple point of Richardson et al. (1969). Roman numerals - contact metamorphic zones referred to in the text. Zone IV comprises two different assemblages IVa and IVb that occur at the same grade in rocks of different composition. In quartz-absent rocks, Zone V can be divided into lower grade (Va) and higher grade (Vb) subzones based on the presence of muscovite (Va) and corundum (Vb), respectively. Reaction numbering in Arabic numerals follows the text except that the ‘P’ prefix is omitted. Isopleths are of (100× Mg/(Mg+Fe)) in cordierite.

(Figure 5) Isograds in carbonate rocks from the Coire Giubhsachain syncline, northeast flank of igneous complex (Paulson & 1997; modified from Masch and Heuss-Aßbichler 1991 and Ferry, 1996a). Numbering of isograds is the same as in the text (with 'C' prefix omitted). Circled numbers and symbols 9, 10, CIII, 15 and 16 refer to assemblages and isograds observed in siliceous dolostones, wheras circled numbers 6 and 14 are for isograds in impure limestone.

(Figure 6) Isobaric T-X_CO2, diagram (3 kbar) for selected equilibria in the chemical system CaO-MgO-SiO₂-Al₂O₃-H₂O-CO₂, showing numbered reactions discussed in the text ( Pattison & Harte, 1997: modified from Masch and Heuss-Aßbichler 1991). All reactions except C18 involve H₂O and/or CO₂. The unlabelled reactions are:  Tlc + Cal + Qtz = Tr + CO_{2 +} H₂O. 18. Gros + Qtz = An + Wo (phases on the right hand side of the reaction are on the high-temperature side)

(Figure 7) Outline of area for field excursions. Geological map showing location of field stops for Day 1 (see (Figure 7) for key to geological map).

(Figure 8) (a) Geological map showing location of field stops for Day 2, see  ((Figure 7) for key to geological map). Corresponding topographic map showing location of field stops for Day 1 (reproduced with permission by the Ordnance Survey).

(Figure 9) (a) Geological map showing location of field stops for Day 2 (see (Figure 7)) for key to geological map) See (Figure 10) for Stop 2-1 (b) Corresponding topographic map showing location of field stops for Day 2 (reproduced with permission of the Ordnance Survey).

(Figure 10) (a) Geological map showing location of field stops for Day 3 Part 1, Fraochaidh traverse, (see (Figure 7) for key to geological map). (b) Corresponding topographic map showing location of field stops for Day 3 Part 1 (reproduced with permission of the Ordnance Survey).

(Figure 11) (a) Geological map showing location of field stops for Day 3 Part 2, (see (Figure 7) for key to geological map). Also shows Day  1, Stops 1-7 1-8 & 1-9. (b)  Corresponding topographic map showing location of field stops for Day 3 Part 2: (reproduced with permission of the Ordnance Survey).

(Figure 12) (a) Geological map showing location of field stops for Day 4 (see (Figure 7) for key to geological map) (b) Corresponding topographic map showing location of field stops for Day 4 (reproduced with permission by the Ordnance Survey).

(Figure 13) (a) Geological map showing location of field stops for Day 5 (see (Figure 7) for key to geological map).(b) Corresponding topographic map showing location of field stops for Day 5 (reproduced with permission by the Ordnance Survey).

Photographs

(Photo 1) (Frontispiece). Overview of the Ballachulish Igneous Complex and Aureole from Tom Meadhoin ridge, looking SW.

(Photo 2) View to SW from the summit of Sgorr Dhearg looking across Loch Linnhe

(Photo 3) View from Beinn Man looking NE to the town of Ballachulish and Loch Leven.

(Photo 4) View of the Beinn a' Bheithir massif underlain by the Ballachulish Igneous Complex and Aureole, taken looking south across Loch Leven from the Onich shore near Stop 1-1. The hill complex seen is referred to Collectively as Beinn Bheithir and the peaks of Sgorr Dhearg and Sgorr Dhonuill form the highest parts of this complex. To the right of the Ballachulish bridge one looks up into the valley of Gleann Chaolais. bounded on the right (west) by the rounded flank of Creag Ghorm (758 m), and on the left (east) by a ridge leading from the rounded shoulder of Meall a' Chaolais up to the slimy) white peak of Sgorr Dhearg (1024 m). At the head of Gleann' a' Chaolais and to the right (west) of Sgorr Dhearg is Sgorr (1001 m) and its subsidiary peak in the foreground, the Devil's Tooth, which forms a prominent cliff-rimmed triangular peak overlooking the head of Gleann a' Chaolais. To the left (east) of Sgorr Dhearg is another more rounded, white peak (unnamed) with a ridge leading down to the rounded shoulder of Beinn Bhan the latter separated from the Sgorr Dhearg ridge by Coire Giubhsachain. The eastern contact of the Ballachulish igneous complex with the host Dalradian metasediments is subparallel with the lower part of the Meall Chaolais - Sgorr Dhearg ridge, but was obliquely across it in the grassy portion of the ridge just above Meall a' Chaolais, so that it lies on the nearside of the Sgorr Dhearg summit. Interbedded metapelitic, quartzitic and calcareous layers of the Appin Group give rise to the generally more angular exposures along the upper parts of the Meall a' Chaolais– Sgorr Dhearg ridge. The while peak of Sgorr Dhearg itself and the white outcrops along the Beinb Bhan ridge up to the unnamed top to the left (east) of Sgorr Dhearg are formed by Appin Quartzite. On the right-hand (west) side of the mountain panorama, the boundary of the igneous complex lies between Creag Ghorm (on the photo) and the next hill (off the photo to the west). Thus most of the ground across the loch is underlain by rocks of the Ballachulish Igneous Complex, which gives rise to generally rounded outcrops. Most of Creag Ghorm and Meall o'Choalais are occupied by various varieties of monzodiorite and quartz diorite (see Coloured Map (Map 1)), the earliest of two main phases of the igneous complex. The second phase of granitic rocks, which were emplaced into the diorites in the central parts of the complex, form Sgorr Dhonaill, the Devil’s Tooth and the upper more southerly parts of Creag Ghorm (hugely out of sight).

(Photo 5) Stop 1-2. Gametiferous phyllite/schist of the Leven Schist lithology, immediately west of the Ballachulish Slide.

(Photo 6) Stop 1-2. Fine grained graphitic black slate/phyllite of the Ballachulish Slate lithology interbedded with dark grey marble of the Ballachulish Limestone lithology (foreground). These rocks lie immediately east of the Ballachulish Slide.

(Photo 7) Stops 1-3 and 3-1. Cordierite porphyroblasts visible as dark patches on cleavage planes of regional phyllites and schists. Note that the size of the patches varies in different parts of the rock. This sample comes from roadside exposures near the parking place for Day 3, Part 1, and shows a coarser development of cordierite patches than at Stop 1-3; but the style of development is similar at both these and other localities in the aureole.

(Photo 8) Stop 1-7/1. Inclusion-rich quartz diorite. The inclusions range from metasedimentary, especially metapelitic, xenoliths, to intermediate-mafic igneous inclusions of similar mineralogy to the host quartz diorite.

(Photo 9) Stops 1-8, 5-4 and 5-5. Interbedded psammite (light layers) and pelitic hornfels (dark, knobbly layers, rich in cordierite+K feldspar+andalusite), from Zone V. The actual exposure in the photograph is from near Stop 5-5, but is similar to exposures seen in the vicinity of Stop 1-8.

(Photo 10) Stops 1-8 and 1-9. Incipient migmatitic features in interbedded pelitic and semipelitic hornfels, upper Zone V. See description of Stop 1-9 for an explanation of the features.

(Photo 11) Stop 3-3. Massive, pitted pelitic hornfels from the high grade end of Zone III. Fraochaidh transect. The pits represent the sites of weathered out cordierite crystals. The matrix surrounding the pits is rich in muscovite, biotite and quartz. Scale bar in cms.

(Photo 12) Stops 3-4, 1-8, 5-2, 5-4 and 5-5. Massive Crd+Kfs-bearing pelitic hornfels characteristic of Zone IVb. The photograph was taken near Stop 5-5 in Coire Giubhsachain, but is representative of Zone IVb in many parts of the aureole. Note the mesh or honeycomb texture, defined by randomly orientated, weathered-out cordierite crystals (represented by pits) within a resistant,  light coloured matrix rich in K-feldspar Note also that the matrix surrounding the pits is lighter colorant and more sharply defined than the matrix in hornfelses from Zone III (compare with (Photo 1) ).

(Photo 13) Stops 3-11 to 3-13. View of a typical exposure of the Chaotic Zone migmatites. Note the isolated fragments of metapelitic hornfels randomly orientated within a granular matrix containing veins. See the description of Stop 3-11 for a fuller description and explanation of these features.

(Photo 14) Stops 3-11 to 3-13. Detail of the Chaotic Zone migmatites. An isolated metasedimentary schollen, with relic bedding still preserved, occurs in lower part and is surrounded hr a granular semipelitie matrix. An andalusite-rich domain occurs just below the scale bar in upper part.

(Photo 14) View of the contact between granite of the igneous complex (light coloured upper crags) and the Chaotic Zone pelitic migmatites (dark lower exposures).

(Photo 16) Stop 4-3. Crenelated graphitic phyllite of the Ballachulish Slate lithology with abundant cordierite porphyroblasts forming roughly ovoid 'blobs'. Characteristic of Zone III in this vicinity.

(Photo 17) Stop 1-5. A crenulated cleavage surface of the graphitic phyllite of the Ballachulish Slate lithology. The short elongate ribs, with widely varying orientation, mark the occurrence of abundant mm- to cm-long andalusite prisms. The full mineral assemblage in the rock is andalusite + cordierite + biotite + muscovite + quartz, characteristic of Zone IVa (see discussion under Stop -1-5). The andalusite in the rock shown is a little coarser grained than in most exposures in ZoneIVa.

(Photo 18) Stops 5-3 to 5-6. 1-8 and 3-5. Randomly orientated andalusite prisms in a massive cordierite+K-feldspar-rich pelitic hornfels (Zone V). The photograph was taken at Stop 5-5.

(Photo 19) Stops 5-5, 1-8 and 3-5. Corundum-rich, quartz-absent pelitic hornfels of Zone Vb. The corundum is risible as abundant small, rounded 'pimples' that contrast with the more prismatic andalusite crystals seen below the pencil (compare with Photo IS).

(Photo 20) Stop 5-6.  Anastomising veins rich in K-feldspar + quartz, within layered cordierite+K-Feldspar-rich pelitic and semipelitic hornfels. The prominent light coloured vein (lower left of photograph) is of granitic material from the igneous complex. See notes of Stop 5-6 (above 560 m) and Stop 1-9 for a fuller description and explanation al the veins and other features. From the ridge/plateau area around Stop 5-6.

(Photo 21) Stop 5-6. Detail of migmatitic rocks with boudin-type structures. The original lithology was of interlayered pelitic and semipelitic material and now shows rigid, pulled apart cordierite-rich hornfels (metapelite) layers (A), ductile semipelitic layers (B) and segregated Kfs+Qtz-rich leucosomes occupying the gaps between the pulled apart hornfels layers (C). Notice how the leucosome merges into the ductile semipelite, giving the impression of being extracted from it. Field of view is 5 cm across. See notes of Stop 1-9 for further explanation.

(Photo 22) (opposite, above). Stops-7. Calcite+spinel (Spl )+Forsterite-bearing dolomitic marble with folded veins of calcite and forsterite. The Forsterite is commonly, extensively altered to serpentine giving the veins a yellow-brown colour on the weathered exposure surface.

(Photo 23)  Stop 5-9. Calsilicate rock rich in grossular (equant crystals) and vesuvianite ( indicated 'vesuv').

(Photo 24)  Stop 5-10. 'Chocolate-tablet' migmatites. See the notes under Stop 5-10 far a description and explanation of the features visible in the top part of the photograph. Cutting across the bottom of the photograph is a lighter coloured dyke-like body of quartz-diorite, carrying many inclusions of pelitic hornfels; boundary picked out with white line.

(Photo 25) Stop 5-10. Detail of 'chocolate-tablet' migmatite. The rock consists of interlayered petite and semipelite. Cordierite-rich hornfels lavers and broken into angular fragments in a tablet structure, with mobile leucocratic material both cross-cutting and running parallel to the layering. The mobile leucocratic material separating the hornfels fragments merges into semi-pelitic layers and does not form extensively cross-cutting veins. Compare with (Photo 10) and (Photo 21).

Tables

(Table 1) a. Principal itinerary of stops for Day 1: Overview of the Ballachulish Igneous Complex, Dalradian host rocks and contact hornfelses b. Optiollal additional stops during Day 1 itinerary.

(Table 2) Itinerary of stops for Day 2: Rock types and intrusive relationships of the igneous complex.

(Table 3) Itinerary of stops for Day 3: Part 1 Fraochaidh prograde sequcnce. b. Itinerary of stops for Day 3 Part 2 Chaotic Zone migmatites and nearby carbonates and calcsilicates.

(Table 4) Itinerary of stops for Day 4: Prograde metapelitic hornfels zones in thc Ballachulish Slate along the Gleann a' Fhiodh–Coire Chaorann ridge: appinite and quartz diorite relations; migmatites and Crd+Grt+Opx hornfelses.

(Table 5) Itinerary of stops for Day 5: Medium- to high-grade interbedded pelitic and calcsilicate hornfelses and marbles; various migmatites, including 'chocolate-tablet' type; summit(s) of Beinn a' Bheithir.

(Map 1) Geological map of the Ballachulish Igneous Complex and aureole. (map in endpocket).

(Front cover) Cover photograph. View looking east from the summit of Sgorr Dhonuill to Sgorr Dhearg. The ridge in the foreground is underlain by granite  of the Ballachulish Igneous Complex. The summit of Sgorr Dhearg, is underlain by white Appin Quartzite or the host Dalradian metasediments. On the left skyline is Ben Nevis and the peaks the Mamore range.