Jamaican Caving Notes
|Caving News||Jamaican Caves Organisation||JCO Main Page|
|JCO Funding and Tours||Contact the JCO|
Mine Exploration and Survey
Report: RS Stewart
Team: RS Stewart, J Pauel
Photos: J Pauel
Videos: J Pauel: Ladder being lowered into the shaft on Jan 10/08 (14.4 MB wmv).
From January 8 to 12, 2008, Stewart and Pauel carried out a mapping survey of a mine abandoned in 1863, in assistance to a company that has hopes of recovering it in the future.
In the past, the JCO has attempted to convince bauxite mining companies to limit disturbance to caves and karst in their lands, with limited success. The effort is not over. However, the mine we surveyed is of a different nature; it's small, deep, and intended only to chase a narrow vein of metals down over 200m into the earth. The tailings, for the sake of economy, will be small. The surface area involved is several hectares in a district that lost its forest cover long ago. The local community will benefit (jobs, which they're looking forward to), and the Jamaican government will collect a percentage. In this case, we don't see a problem.
The assignment was taken on for funding purposes. The JCO simply cannot endure without some input of money. To date, we are running a deficit of thousands of dollars (Cdn/US), and the head of the group, the writer of this report, is going broke trying to keep it alive. Thus the funding. We make no apologies for it.
We cannot give any positional details in this account, or post the maps that resulted from the survey (for proprietal reasons), but our efforts in carrying out the assignment deserve to be described, something that was not done in the report submitted to the funding group. The techniques used were new, at least for us. The work required was considerable.
The fieldwork began on January 8, 2008. I'd arrived the night before, and Jan and I had stayed up late, sorting and fine-tuning gear, while quaffing a few cold ones. This meant, of course, that our departure from Kingston in the morning was later than hoped. However, the group from the mining company whom we were to meet en route were running just as late, so it wasn't a problem. After linking with them at a gas station in Kingston, and a "follow we", we were on Highway 2000, with us in Jan's kriss new Landrover, and their crew in a van. At Old Harbour, we turned north. At this point, my account becomes intentionally vague, but it can be said that the drive up into the hills supplied some of the best views I've ever had in Jamaica.
The entrance to the mine shaft is located downhill several hundred metres from the nearest minor road. The track is steep in places, but manageable. Fortunately, the funding company had arranged for excellent local support crew, and transport of gear was not a concern. At about noon, we were at the entrance pit, peering down, and preparing for the first descent into this hole in 145 years.
The plan for the first day was straight recon, to determine what we faced in accessing the mine. If possible, bolts would be set at the entrances to connecting galleries, to facilitate getting on and off rope from the shaft. To that end, I had the hammer, the hand-drill, and several bolts with hangars dangling from my harness, attached with thin static line and carabiners. Because there were concerns about bad air, I also had a small SCBA tank in my backpack with the hose and mouthpiece extending out to where I could easily grab it. All in all, it was a bit of a load and it took a while to get everything properly rigged.
Fortunately, several convenient trees are located around the perimeter of the shaft. A particularly large one, well-placed, was used to anchor the 100m 13mm "Monster Rope", and this was then fed into the hole. (This anchor would become our tie-in point for the surveys in the following days, including geographically by way of the GPSr and antenna.) A bit of gardening of loose rocks around the top was done, and then I got on rappel. The manouevre involved was appropriately dramatic for the attendant audience (several geologists, half a dozen local crew, and the concession holder). The point at which I would actually first hang on rappel was several feet below the lip of the shaft, and it was necessary for me to start the descent by sliding/scrambling that distance (with the descent rack already on the rope, of course). This wasn't a problem, and indeed something we often have to do. However, the onlookers had never seen cavers or climbers in action before, using single rope technique. And they all regarded the hole as mysterious and forbidding (none of them had even hung out over the top to look straight down). The silent, strained stares indicated that at least some of them fully expected to watch me die as I entered the pit. With a quick slide, I hit tension, and then announced, "On rappel". One quiet voice above said, "That takes faith..."
A quick look down revealed water pooled in the depths, reflecting the sky above. The distance was hard to judge, but I guessed it at about 40m. Feeling rather disappointed, I told the others what I saw. Jan suggested that it might just be sitting on a ledge, and I agreed that it was a possibility. But the senior geologist on the scene, Peter, immediately guessed that it was the high point for water that drained out of a known choked adit, downhill to the north. The surveys we subsequently carried out showed this to indeed be the case, and it is very impressive how quickly he figured it out. However, the task at hand was recon, and accordingly, after trying and then abandoning a fifth bar on the rack, I headed down.
Radio communications were more than adequate; Jan and I had 4 GMRS 5W handhelds between us, and the local crew had a couple of others. At about 30 metres down, I tied off the rack, and then used the radio stashed in my vest pocket to file my first report. Around me, the shaft had widened from under 3 metres to over 6, and a small tunnel connected on the far side (southeast). The shape of the junction was obviously terrible for getting off rope and into the passage: Where the tunnel hit the shaft, it widened, becoming funnel-shaped in both width and height. This resulted in a steep, dirt-covered access slope coming up from below, and a deep overhang above. The level part of the tunnel was set back over two metres from the closest place a rope could hang. The only option for bolting would be to set a series of them, horizontally, from the shaft wall outside of the "funnel" all the way to the level passage. It would take at least six, and be very time-consuming. When this news had been transmitted to the top, I tied a flag on the rope to mark the passage level, and then resumed my descent toward the water.
The shaft narrowed again below the opening to the passage, returning to the width found in the upper section. It was a very short drop the rest of the way, down to the water, and within a minute, I was hanging about a metre above it, and tieing off the rack. I intended to keep my feet dry while I took a good look at things.
The shaft again widened right above the flood point. To the left, inwards with regard to the hill in which the mine is located, the rock was scooped out creating a visible pocket of a couple of metres, with it flooded in the lower section. To the right, outwards, the shaft appeared to cut back, overhanging, although this was entirely underwater. Above, an old pipe, about 75mm wide, curved out of the water and then back in, with this loop extending across the width of the shaft. On the pipe were several very archaic looking fittings. I could not clearly see through the water to any depth, and so eased down a little more on rappel until my feet were about 20cm from being wet. Using the brightest beam of my headlamp, a 3W LED, I attempted to see what lay below. This was made difficult by leaves and bamboo floating on the surface, but I was sure that at least on the left side I could see a bottom. On the right, outwards, I couldn't tell. After communicating this information to the top, and tieing a flag on the rope at the water level, the recon was essentially complete and I began my ascent.
My ascent up the rope was quite enjoyable, thanks to new and improved gear. For the first time, I was using the rig that Jan had changed to earlier in the year. This deserves some detail: In the past, I had used two Jumar ascenders - one for the chest, and one with two footloops hanging from it, above the chest. On the lower part of the ascents, there was always a problem with the chest ascender dragging the rope up with it when I stood in the footloops, especially when mud was involved. The new method used a third ascender, a little Petzl unit, which mounts on the right foot. The upper ascender now had only one loop, to the left foot. Consequently, when I stood up, the right foot held the rope down, enabling the chest ascender to slide up the rope with no drag. I had also adjusted everything as well as possible, and I was stepping up a maxiumum distance every time. I am totally sold on this method, and it's what I intend to regularly use in the future. I have to thank Jan for giving me the foot ascender as a Christmas present, because if he hadn't, I wouldn't have spent the bucks, and would still be yanking rope through the chest ascender for the first 30m of every climb.
Once back at the top, I gave a fuller account of what I'd seen. This was followed by pulling the rope and measuring the distances to the flags. By comparing things to a map of the mine based on the literature, our best collective guess was that the passage partway down was the first level (listed at 132 ft, and measured at 37m), which was supposed to have an adit to the exterior surface, and the water was possibly at the supposed third level, which also had an adit. This would make sense as the known adit, located on the hillside, blocked partway in, had water draining from it (used by the local farmers for irrigation, via hoses). However, the water level was at minus 57m, rather than the stated 276 ft, and the supposed second level, at 204 ft, which was close to the flood level, had no adit. There was also a third, lower adit listed. The best way to sort things out was to survey down the hill to the entrance of the exterior adit, to see how it matched up with the interior flood level. That would have to wait until another day, as the afternoon was well advanced. We called a halt to the day's activities, and then after discussions with the geologists on our plans for the coming days, we headed back to Kingston.
The second day, Jan 9/08, was devoted to finding a way into the first-level passage, from the shaft, and carrying out the external survey to the adit entrance. At about 11:00 AM, we were back at the shaft, and had the 13mm tied again to our previous anchor and in the hole.
Our plan was to first have me descend on the 13mm rope from the previous anchor, and, by using a compass when I reached the junction, determine the direction that would bring the rope closest to where we could set bolts to access the passage. This bearing would be radioed up to Jan who would use a second compass to find an anchor in the required direction. Accordingly, I rapped down to a point directly across from the junction, tied off the rack, and pulled out the compass. I decided to go with the wall just to the right of the passage junction. The bearing was taken and sent up to Jan, who reported that there was a good tree in the right direction. I changed over to ascent and was back up in about ten minutes, moving quickly on the new vertigear rig.
We decided to tie a second line, the orange 11mm, onto to the chosen tree. When this was accomplished, Jan headed down on rap to have a look. Soon after, he reported via radio that he was still a long distance from the wall, with no chance of reaching it to set a bolt. As we soon realized, the shaft above narrowed and angled enough to create an effective bottle-neck for the ropes as they hung in the hole, pushing them to within a metre of each other. As nothing was possible, Jan changed over to ascent, and returned to the surface.
Discussion ensued. It was obvious that we would need a pole of some sort to extend across the shaft, sticking into the passage, which we could use to drag ourselves sideways while hanging on rope. But what kind of pole and how would we mount it on the opposite wall. Jan recalled seeing nothing promising. Eventually, brain-storming supplied a solution: We would use a ladder, with legs on the slope below the passage, perpendicular, leaning against the far wall of the passage, at an angle. This would get us to just below the passage entrance. Then, we would place a few bolts upwards to get in. But first, we would need a ladder, so it was put off until we could clear it with the funding group. For the rest of the afternoon, we would carry out the downhill survey.
A new survey rig had been prepared for the assignment, consisting of a Disto A2 laser range-finder and SmartTool digital clinometer mounted and aligned on a length of of L-shaped perforated steel, in turn mounted on a light-weight tripod. The Disto/clino set could be detached from the tripod when necessary. However, for this first survey, down the outside of the hill in bright light, the tripod was used to stablize the laser and lengthen the shots. We also used a target: a sheet of laminated white paper that had the literature-based map printed on it. The laser was aimed at a particular point on the printed map, the shaft/third-level junction, and the plastic finish of the sheet reflected well enough to enable shots up to 30m as long as the laser was slightly to the side of the printed junction. Bearings were taken with my trusty Brunton Eclipse.
The survey downhill was not particularly easy due to a slope of 40 degrees in places, and a surface of bamboo debris and leaf litter, but we managed. Over an hour later, we had the last shot, reaching the adit entrance at the drip-line. A quick look into the adit followed. The passage was u-shaped, curving at the top, with a flat, partially-flooded floor. Water trickled out, and several hoses were laid in the pooled water inside, siphoning it out and downhill for irrigation on a nearby farm. The width of the passage was not much more than a metre, and the height less than two. Some ten or twenty metres in, a blockage of dirt and stones could be seen. We elected to keep our feet dry and not enter, since we would have to return another day, anyway, to shoot back up the hill and close the loop.
We began our return to the top, expecting it to be a challenge. However, a five-minute scramble up the steep hill, which we had spent over an hour surveying down, brought us back to the shaft entrance. Gear was assembled and stowed, and then we hiked up to the vehicles, stashed everything, and finished things off with a round of cold Red Stripes.
The third day, Jan 10/08, saw us rolling through the hills north of Old Harbour, en route to the mine, with a 24 ft extension ladder tied to the top of the Landrover. The time required to obtain said ladder in Kingston, and get it on the roof of the truck, meant that we weren't at the hole until about noon. However, we were there prepared for a total assault on the passage junction. In addition to the ladder, we had our three longest ropes, bolting gear, pulleys, spare ascenders, and a very dependable surface crew.
The approach was to first lower the ladder into the hole in its unextended form (about 4m long) until it was about 5m above the junction. To determine this, we first measured and marked the lowering rope using our numbers from the first day. The tie-on point was a rung on the upper part of the lower section. Our local crew hoisted it, and then slid it down the hole, beside what would be our third anchor, directly opposite the junction bearing. When the marked point on the rope reached the anchor, it was tied off in a way that would leave it easy to adjust. [Video of the ladder being lowered down the shaft - 14.4MB wmv.]
Our plan was to put both Jan and I into the hole, on two lines, so that we could move the ladder into place. For some reason, I'm not sure why, I rapped down first on the 13mm (I believe my thought was that I'd go ahead, let Jan know how it looked by radio, and then he'd come down). This turned out to not be a good approach. I reached the point in front of the junction, tied off, looked around, and then let Jan know he could get on rap. As soon as he started moving down the wall at the top of the shaft, loose rocks began to tumble toward me. The upper few metres is surrounded by highly fractured andesite, sharp-edged, and heavy. It hadn't been a problem before, because we'd only had one at a time in the hole. Fortunately, I could just reach a tiny edge of rock on the wall, and haul myself under a little overhang as the rocks raced past. I radioed up to Jan to stop moving and that I'd come up to him. This was done, then we both climbed out of the hole to catch our breath. I was also able to suggest a change of plans because of what I'd seen with regard to the ladder - it had been right where we'd wanted it, depth-wise, but it was obvious that it wouldn't fit from passage slope to opposite wall - part of the shaft wall above the junction was in the way. But, I'd spotted a little ledge on the far side, lower down, that the feet of the ladder might sit on, with it angling upwards into the passage. That's what we'd try.
The obvious solution to the rockfall, and what we would have done in the first place if I'd been thinking, was to have both of us go down at the same time on the two lines (13mm - first anchor, 11mm - second anchor). So, after a short break, we got on our separate lines and rapped down together. There were no problems, as those few stones that let go were below both of us. In fact, it was really quite cool - it's the first time we've ever had two people on a pitch like that - usually, you're alone, except for a radio.
We were in place, just above the junction, within a few minutes, and then tied off the racks to examine the situation. The position was this: Jan was toward the passage-shaft junction. I was further away by about a metre. Further still toward the far wall was the ladder (after some lowering from the crew above), although also about a metre in a perpendicular direction. On the far wall, opposite the junction, and about 3m lower, was a tiny, sloping shelf, about 60cm deep and 3m wide. All three of us, Jan, me, and ladder, were hanging in the air, on ropes.
First, we had to extend the ladder. This was possible since it was hanging from the rope only on the lower section - the upper would move forwards. We slid it about half-way, and then turned our attention to getting the feet on the ledge. This proved to be very difficult. Essentially, it was like working in a zero-gravity environment, although in only two dimensions. Newton's Laws applied everytime we pushed and pulled, with equal and opposite reactions. The three floating bodies involved swung in bizarre motions, back and forth in the shaft. After a few minutes of this, we decided the pivot point of the ladder was too high, so radioed up to have it lowered a little more. Bit by bit, our dependable crew up-top inched it downwards. We called a stop and tie-off when it looked best, and then tried again. We couldn't quite get the feet to stick on the ledge, so we decided to see if we could somehow put me on it instead, to begin with. I wasn't that far from it, and with a bit of swinging... Jan began to repeatedly shove on my back with his foot, a little above me, setting up a pendulum. Within a couple of swings, I was very close. A few more, and I was almost getting my feet on it. I was a little too high, and didn't have enough weight when I reached it to stay put, so I rapped down about 10cm more, tied off, and we swung again. After about 6-7 tries, my fingers grabbed a little edge on the wall as my feet hit the ledge, and I stayed on it, wavering for a few seconds. We both let out a cheer. Now, I could grab the feet of the ladder while Jan pushed it, and get them in place.
We had the feet of the ladder on the ledge fairly quickly, with Jan shoving the ladder my way and me lifting the legs, but it was unstable as hell. Only one foot was in contact when the ladder was level across the length of the rungs; the other was about 20cm above the part of the ledge it hit. This meant that for the rest of the procedings, I would have to hold the bottom of the ladder in place. So far, all we had done was attend to the bottom end. The top was not yet into the passage junction. The ladder was not fully extended, too short in its current configuration, and was angled about 30 degrees too high. Jan would have to take care of most of that, as I was restricted to my little perch.
We decided to first adjust the angle. Instructions were radioed up to slowly lower the ladder. The tie-in point, with the ladder partially extended, caused the ladder to assume the proper angle as the rope was lowered, and it came to rest against the wall of the shaft well to the left of what we would need to enter the passage. We called a stop, and tie-off, up to the surface. Jan now began to push and kick the ladder to the right, swinging against it, as I held the bottom in place. From my viewpoint, what he was doing looked impossible, at least in terms of physics. He somehow managed to move the upper end of the ladder well over two metres from where his rope hung. Somehow, it came to rest directly below the passage. All we needed to do now was extend it, and force it up into the junction.
The ladder had a rope and pulley on it to aid raising the upper section, so as Jan shoved while hanging on rope, I pulled the rope and held the feet. Rung by rung, it extended, as Jan hoisted the top end up the wall, and I heaved on the rope. After a few minutes of heroic effort, we actually had it in place. We couldn't believe it.
Now came the the delicate traverse into the passage. I remained on my little ledge, holding the feet, as Jan eased himself onto the ladder. Once on, he carefully worked his way up toward the passage, still on rope. The ladder teetered as I held it. With a final couple of moves, he was in.
The first thing he said was, "Shit, Stef, it's a dead-end!" But, as he attended to ropes and gear still attached to him, he happened to turn around and look in the opposite direction. "Man, it goes this way! There's a long passage, just like the outside adit!" This was very good news, especially because of all the work we'd done to get into the thing. Apparently, we'd discovered the First Adit, said to exist, but with no exit on the hill outside. The bearing was right, and with that distance, it had to be.
Unfortunately, I couldn't join him to look myself. I couldn't cross the ladder, because it would slip off the ledge if I let go of the bottom, and anyway, I had to keep it in place for Jan to safely get back on rope in the shaft. Without the ladder for the first part, he'd have to drop before he hit tension, and then take a brutal swing into the far wall. However, Jan was well equipped for recon. He had a camera, a good quality videocam, and much light. As I sat on my little rock, he headed off along the adit, videoing as he went. His light disappeared after a few minutes, but I could hear his voice-over commentary for the video coming faintly into the shaft. After about 20 minutes, he was back, and preparing to get on rope for his return ascent.
The survey of the passage still remained to be done, but we would have to fine-tune our rig first so both of us could get into it. This would be done the next day, by placing a bolt in the shaft wall to hold the feet of the ladder in place. For now, we'd made good progress and expected to successfully knock it off. Once Jan had carefully descended the ladder partway, and then slipped off to hang on rope in the ascent mode, I eased off the shelf, on rope, and we ascended together.
It was after sunset when we reached the surface. The ropes were left in place, and after assembling all the gear that would go for the night, we hiked up to the Landrover to drink a couple of well-earned, cold Red Stripes, fresh from Jan's cooler. Soon after, we were homebound to Kingston.
The next morning, Jan 11/08, we were at the shaft and preparing for descent earlier than any of the previous days. There'd been no need to carry ropes and re-rig the drop since everything was already in place (and undisturbed, as promised by the local crew). Jan would again take the rope hanging from the second anchor, and I would use the 13mm, from the first anchor. Anticipating success in our attempt to enter the passage, I had the survey rig, including tripod, stuffed into my backpack. From my harness hung the hand-drill, hammer, and several bolts with hangars. I also had a long length of tubular webbing, but as I would realize when it came time to use it, no knife with which to cut it. I have had several knives over the years that I've brought to Jamaica, but invariably, everyone has been borrowed by someone who has used it to prepare a recreational smoke, and they have then become useless to me, as they can't be taken back into Canada when I return. As a result, I simply stopped buying them some years ago. However, I digress...
Again, the two of us went down on rappel at the same time, with only minor rockfall problems (a few little ones dinged Jan, dislodged by his rope above). Once at the ladder, which was still stretched across the shaft 37m down, five or ten minutes of swinging got me back on the shelf. I held the feet of the ladder in place as Jan climbed atop and gingerly ascended into the passage, and then turned my attention to the placing of the bolt. The stance was very awkward: I was crouched on a small flat rock, facing outwards with my back on the wall, with the area where the bolt would have to be placed to the right, on the other side of the ladder. There were no options in my position: it was the rock or nothing. A few tentative taps with the hammer and drill showed that I would either have to hammer with arms crossed, or with my left hand. Whichever way, it would take a while, so I suggested to Jan that he start examining the passage for any signs of ore while I worked on the bolt. He headed off with lights on full power, and I started to drill.
Incredibly, I made progress. The rock was hard, volcanic andesite, and even though I was prepared with a new SDS bit and Petzl SDS hand-drill, I'd expected it to be very, very tough. A few minutes of using my right hand to hammer, crossed over my left arm, was replaced by hammering left-handed. Several minutes more, and I had a hole about 4mm deep. Now, the bit easily stayed in place, and I was able to loosen the grip a little on the hand-drill to get the SDS bounce. The pace picked up. After I was in over a centimetre, I could start giving it a decent whack (as well as my left arm would allow), although not so much that I'd mess up the end of the bit, which I'd been warned about. A light tap, then a firm whack, and then a twist that transmitted the feel of the crunch of rock within. This was my first experience with this kind of rig, and I was very impressed. I carried on steadily, checking depth every few minutes, and after a total of about thirty minutes had the hole a little deeper than it needed to be. I'd gone for the extra depth just to make sure the bolt actually went all the way in - with the Hilti expansion boles we were using, too deep is no problem. The hangar was clipped into to my short cow-tail, with the bolt already in it, so there was no fear of losing anything. I placed the bolt into the hole and tapped lightly on the end. It was a very tight fit compared to the Petzl anchors we've used in limestone. I tapped more firmly. It grudgingly moved in about halfway. The thought went through my mind, "What if this sucker won't fit??" In for a penny, in for a pound, I started whacking it. It slowly moved inwards, until it finally reached the proper depth. There was certainly no doubt that it was solid, so I began to crank the nut inwards, with it firming up nicely against the hangar after just three or four turns, the recommended number for the bolt. I yelled up to Jan that I had the sucker set and was going to tie-off the bottom of the ladder. Within a minute, he was back to watch. I used a portion of the long length of webbing to tie into a carabiner on the hangar, with the attached remainder of it sitting on the shelf, and then wrapped it around the bottom rung and side-section. It was tightened, and a little testing showed the ladder to now be totally solid on the shelf. I could finally get into the passage.
The crossing of the ladder was a bit tricky; it wobbled, various ropes hung in the way, my boots were muddy, and I had a high centre of gravity thanks to my pack, but a couple of minutes of careful movement, and cursing, took care of it. After tieing off my rope to a large rock, and unclipping vertigear, I could finally look around. To the left, the passage that could be seen from the shaft extended about 12-13m, ending in heaps of dirt and rocks. To the right, a passage almost identical to the adit we'd looked at on Day Two extended off into the dark, with the end unseen. It seemed like an odd sort of cave, rather than a mine. Before the fieldwork had begun, I'd envisioned finding shoring, struts, and beams. Instead, we were in simple tunnels through the rock. The morphology was strange for a cave, but all in all, it might as well have been one.
Now came the survey. There were no formations to use as a first station, so a rock with an easily remembered shape was placed on the floor of the passage where we had the three necessary sight-lines: out, to the rope, and along the two sections of the passage. First, a series of survey legs were taken to, and from, the blockage at the end of the adit passage. This passage extends in a NW direction, sloping very slightly downwards, and at one time hit the outside at the closest point in terms of the surface topography, on the side of the hill above a short, narrow valley. Next, several legs were done in the short, inwards passage. This passage extends to the SE, cut into the hill, away from the valley.
The adit passage is entirely through andesite with no obvious porphyry, except for two narrow, vertical bands of jarosite. The jarosite is seen as a surface deposit, gold in colour. Chipping showed the base rock to be andesite. A magnetic anomaly was noted, and adjusted for, in the area of the jarosite.
The SW, inwards passage is at first andesite then changes abruptly to a white coloured rock which we believed to be limestone. Small speleothems were present on the ceiling and on the floor below. The width of these was from 5 to 20mm. As we know the mine was last worked in 1863, it supplies a depositional rate, although the geology of this site is very different than a limestone karstic area. Remarkably, the speleothems had a bright blue coating, believed to be from copper minerals in the rock above.
We learnt afterwards from one of the geologists that the white rock was in fact not limestone, but hydrothermal calcite. The material has not been deposited in a marine environment by creatures such as foraminifera, but was injected into large fissures by hot water during the period when the volcanic hotspot was still active. Presumably, the calcium and carbon involved had a biological origin eons before, but it had been on quite a journey getting there. To put things into perspective: Andesite is a volcanic rock created from magma. It is named after the Andes mountains, where it is common. It comes to the surface as part of a plate subduction process (one plate slides under another). The plate that's subducted drags down marine sediments and a lot of water with it. When it's been pushed down far enough, it creates hotspots, volcanos, that bring magma to the surface. As the magma pushes up, it melts off chunks of the continental plate above it (seen as porphyry). Calcium carbonate, the limestone, has been sucked in at some point, disolved in hot water, and then deposited in big cracks hardened out of the volcanic rock. In comparison, regular karstic limestone has been created by the gradual accumlation of tiny marine shells, and although it might have been tilted, folded, and recrystalized, it's still where it started out ages ago, once plate drift is taken into account.
About an hour was spent on the survey, and then we worked at getting chip samples from the area of the jarosite. For this, we had a geological hammer that had been lent to us, but no safety glasses. The chipping consisted of sighting the mark, then swinging the hammer as hard as possible while closing your eyes. It took a while, but it worked. The samples were stashed in cloth bags we'd been supplied with, and then went into Jan's backpack. Once this was done, we were ready to return to the surface.
To exit the mine, we had to carry things out in reverse. First, I went down the ladder to my little ledge. Then Jan followed, but stayed in place partway down the ladder. The extraction of the unit required some adjustments. We had to have the ladder in a vertical position when it was pulled out, but we couldn't simply tie the rope onto the uppermost rung - the bottom of the extension ladder would have slid off into the depths - we also had to tie the two sections of the ladder together. Our existing attachment point was still on the upper part of the lower extension. In short, about 15 minutes passed before we had it sorted out. This included Jan getting his knife to me so that I could leave some of the webbing in place on the hangar, but not the entire length - for that, I believe we used the little haul rope, with it wrapped around the knife. With it all finally taken care of, Jan eased off the ladder to hang on the rope in ascent mode, and then I did the same off of the ledge. Ten minutes later, we were back up top.
It was sunset when we exited, and there was much gear to pull. First came the ladder. Our local crew hauled on the rope, and accompanied by banging and clanging from the depths, it rose out of the hole. Next came our two SRT lines. Then coiling of ropes and stowing of gear. And finally, the hike up the hill to the Landrover to get everything stashed and tied on. It was well past dark when this was completed.
It had been our original intention to roll out of the local village immediately at the end of the day, due to reports we'd received that morning of wild rumours about our activities at the mine (stealing buckets of gold), but because we felt so satisfied with our accomplisments, we instead decided to stop and do an outreach session. This consists of stopping at the most popular bar/shop, hauling out Jan's spiffy laptop, and showing photos and videos of what we've done, while explaining why we did it. All accompanied by drinking cold Red Stripe, of course. A pleasant hour was spent engaged in this important activity, with no problems or accusations about buckets of gold, and then at about 7:30 PM, we finally hit the road to Kingston.
Jan 12/08, the last day of fieldwork, was spent tieing-up loose ends. We still needed to close the loop on the exterior survey, take shots from the rope to our first station in the passage, and explore the bottom of the shaft.
The exterior survey began at the innermost accessible point of the Second Adit, which is a blockage of dirt and rocks. Only one shot was required to reach the entrance, and then the rest of the shots backtracked our survey of Jan 9/08 to the main anchor, thereby closing the loop.
The most notable feature of the Second Adit is the rock it runs through, this being andesite with abundant feldspar porphyry up to 10mm wide. The andesite inside the mine at the First Adit had no obvious porphyry. The vertical distance between the two levels is only 22m and the horizontal distance from the shaft to the Second Adit blockage is 72m. In total, we saw five different mineral and rock types in the 60m high by 102m wide surveyed section of the mine: jarosite, andesite, porphyritic andesite, hydrothermal calcite, and a copper compound staining on calcite speleothems.
The survey had not yet been tied in satisfactorily between the first level adit and the main anchor, and in turn the exterior shots. Once again, Jan and I rapped down the two shaft lines simultaneously. When we reached a point where I had a clear line of sight to the main station on the First Adit level, we stopped, tied off the racks, and I took a shot using the digital rig and compass. I flagged the rope at the "from" point, to measure up-top, and we then carried on down to the water, at minus 57m.
Jan had a look around, and then rapped into the water and got off-rope. I stayed above, using the video camera, with my feet on the old pipe and my back against the wall. At first, he swam around the flooded shaft, but then submerged several times in front of the suspected entrance to the second level adit. At one point, he was down over a metre and I had concerns that he might have gear tangle in hidden pipes or debris. Fortunately, he didn't, and was able to determine that the flood water might indeed be at the second level, with drainage happening through the blockage that we'd observed from inside the Second Adit, on the hillside. After about 15 minutes of swimming and diving, he got back on rope and hauled himself out of the pool. We had now essentially finished the fieldwork, having just a final ascent ahead of us, and then measuring of the rope, stashing of gear, and the hike back to the Landrover. All went well, and we were outbound, back to Kingston, not long after sunset.
Much of Jan 13/08 was spent in turning the survey data into an preliminary map to deliver to the mining people. The plan had been to leave it for a couple of days, but it was unavoidable (a long story). This prevented me from visiting Nicki in Norwood as I'd intended to. I flew back to Canada at 8:00 AM the following day, having had no time off during the session to see her. Quel triste.
|Jamaican Cave Notes - Main Page|