We finished the drilling in the Barberton project at the start of May with completion of hole BARB5 in the Barite Valley. At this stage all our funds for the project were exhausted and we were required to cancel drilling of the final hole, which was planned to sample the silicified komatiites of the Mendon Formation. A complete list of holes and their depths is listed below. BARB 1 total drilled: 420.0m BARB 2 431.37 BARB 3 899.59 BARB 4 538.55 BARB 5 763.23 Total 3052 m Core recovery was excellent in all holes, typically better than 98%. Downhole geophysics (acoustic and optical televiewer, magnetics, natural neutron spectrometry) was completed on hole BARB 3. The core is now housed in facilities on the campus of the University of the Witwatersrand. Cutting, photography and logging are complete for two holes, BARB1 and BARB4 and the logs of these two holes will soon be published on our ICDP and South African websites. For the other holes, the logging and photography will be terminated by September. At that stage we will publish comprehensive summaries of the lithologies and structures sampled in each hole, and will open a call for proposals to work on the core. This call is open to all scientists and students interested in working on the core, but priority will be given to individuals or groups that have been directly involved with the drilling or from countries that provided financial support for the project. Decisions concerning the distribution of core and the research to be done will be made by the steering committee. A workshop to discuss the results of the project and the distribution of core will take place in Johannesburg, probably in the latter part of February 2013. A short trip to the Barberton belt to visit the drilling sites and see something of Barberton geology will also be arranged, if there is sufficient interest. In addition, a special session on the drilling project is planned for the EGU meeting in Vienna from 8-12 April 2013.
The Fig Tree Formation hole (BARB4) has been successfully completed. It emerged from sedimentary rocks, the target of this hole, at 430m, then penetrated about 70m of altered ultramafic rock. It was terminated at about 500m. The rig has now been transferred to the fourth site, in the Barite Syncline, where hole BARB 5 will be drilled. The drillers decided they had not enough space to operate at the site we had chosen and the hole was shifted about 30 m to the southwest. The coordinates of this site are 25deg 54.442'S; 31deg 03.525'E. The hole is now at 146m and we are making good progress through fine-grained shaley and siliceous sedimentary rocks. Drilling is continuing on the mega-chert hole, BARB3 in the Buck Reef. We are currently at a depth of 815 m and still we have not emerged from normal black and white banded chert. If we are still in chert at 850m, 50 m past the target depth, a decision will be made about whether to continue to reach the stratigraphic target. The rate of drilling is still slow, no more than 1-3 m per day.
The Fig Tree Formation hole (BARB4) has been successfully completed. It emerged from sedimentary rocks, the target of this hole, at 430m, then penetrated about 70m of altered ultramafic rock. It was terminated at about 500m. The rig has now been transferred to the fourth site, in the Barite Syncline, where hole BARB 5 will be drilled. The drillers decided they had not enough space to operate at the site we had chosen and the hole was shifted about 30 m to the southwest. The coordinates of this site are 25deg 54.442'S; 31deg 03.525'E. The hole is now at 146m and we are making good progress through fine-grained shaley and siliceous sedimentary rocks. Drilling is continuing on the mega-chert hole, BARB3 in the Buck Reef. We are currently at a depth of 815 m and still we have not emerged from normal black and white banded chert. If we are still in chert at 850m, 50 m past the target depth, a decision will be made about whether to continue to reach the stratigraphic target. The rate of drilling is still slow, no more than 1-3 m per day.
Drilling stopped on 14th December for the Xmas break. It will start again in mid January We are progressing at two sites. The Buck Reef hole (BARB3) is at a depth of 715.55 m and it is STILL in chert, making a total of some 500m of this beautiful but hard to drill rock. The middle Fig Tree hole (BARB4) is 325m and is drilling the wonderfully coloured and structured ferruginous cherts and jaspers illustrated in the photos. Here is a description based on photos of the core, from Don Lowe: The bright red bands are jasper (chert containing hematite or another form of oxidized iron), the dark maroon bands are hematite or mixtures of chert and hematite, and the white bands are pure chert. The pale greenish bands may include both clayey layers and chert layers that contain small amounts of clay and/or siderite. I do not see any sandstone beds in this core in the photographs. Compared with most outcrops of this unit, there is more white chert interlayered with the jasper and hematite bands in the core, but with the abundant jasper and hematite bands, I would call this banded iron formation (BIF). In Barberton, the rocks that we call banded ferruginous chert (BFC) lack jasper and hematite layers, usually consisting of chert bands, bands rich in siderite (iron carbonate), and often but not always clayey layers. There should be some BFC in the core as well as BIF and, in outcrop, both locally contain a few turbiditic sandstone beds. This stuff is a real mixture, which is why it is so interesting sedimentologically.
After passing through almost 200m of ultramafic rock, drilling is proceeding slowly through the tough cherts that make up the Buck Reef. We started with NQ core equipment. i.e. a hole size 75.6mm and core size 47.6mm, and with it our advance in the chert was a magnificent 3m in 24hrs. We subsequently changed to a TNW bit which has the same hole size of 75.6mm and a core size of 60.5mm, giving us the double advantage of larger core and a faster rate of drilling (the reason for starting with NQ is that it is a wireline technique which, when used in normal rocks, is a very much faster drilling technique than TNW which requires that the entire rod string is withdrawn after each run). The thin-walled bit allows three times the penetration in the chert. A picture of the different core sizes is attached for information). We are now drilling at about 8- 10m per day and have reached a depth of 250m, about 50 m into the chert.
Drilling is proceeding at two sites: BARB1 - Komatiites and basalts of the Tjakastad region and site BARB2 - Buck Reef Chert Site BARB1 Komatiites and basalts of the Tjakastad region. BARB1-1, the first hole, was initially drilled to a depth of 122.37m through the tumulus unit and overlying komatiite flows and hyaloclastites and terminating in a dolerite dyke. After preliminary logging the core was shipped to Wits University in Johannesburg. BARB1-2 was drilled from 19th July to 11th August to a final depth of 431.47m. The core intersected a series of komatiite flows, some with olivine spinifex, overlain by komatiitic basalts and terminating in a hyaloclastite unit. The komatiitic basalts were pillowed or massive, and some thick units are differentiated into pyroxene spinifex upper portions and lower pyroxene or olivine cumulates. Interstitial zones between pillows are filled with calcite and some minor sulfides. The original plan at hole BARB1-2 was to drill to 600m, but due to the metamorphosed nature of the extracted material, more specifically a probable lack of fresh olivine and other magmatic mineral, we decided to terminate at 431.47m. The rig was moved back to BARB1-1 with the objective of intersecting at depth a thick komatiite flow that contains fresh olivine at the surface. We anticipate to deepen this hole to a final depth of approximately 318m Surveying to determine the exact alignment and dip of hole BARB1-2 was completed on Thursday. The core from hole BARB1-2 was transported back to Johannesburg. Site BARB2- Buck Reef Chert. On Monday 8th August the rig was in position on a platform that was made for us specifically for this purpose into the hillside by a civil contractor who works for York Timbers. Axel and I walked along the hillside above the drill section together with PhD and undergraduate students from Berlin and Johannesburg to inspect what we expect to intersect at depth. Drilling could not start until Tuesday when the casing was inserted due to problems in setting up the water supply (snow, freezing conditions and solid water). Contractors were busy at the beginning of the week laying a pipeline from a spring, several hundred metres away at the base of Buck Ridge, up to the drill site with four petrol pumps conected in series along the pipeline. A sump was dug and operations were temporarily delayed due to technical problems and a leaking water container. The first core from hole BARB 2.1 was extracted on Wednesday and by Friday drilling had reached approximately 45m into the ultramafic intrusion at the top of the section. Initial logging shows this intrusion to be internally homogeneous and heavily serpentinized. On Friday morning we had a visit from Dr Shoichi Kiyokawa of Kyushu University Japan along with his PhD student. We visited the drilling site and walked the section in outcrop up the hill. We expect to intersect the first chert in this hole at the beginning of next week. Internet access is not possible in the mountains at this site and has delayed reporting our progress until now. (Progress Report: 8-13 August Paul Mason, Utrecht University and the drilling team of the Barberton ICDP project.)
The second hole on the Tjakastad site has reached a depth of 150m. We first intersected a thick komatiite flow but the rock was broken up and variably weathered. Deeper in the hole were a series of komatiitic basalts, some with pyroxene spinifex. The hole is planned to be 600 m long and we hope to intersect more komatiites, some with fresh olivine. A second rig has arrived but its access to the Buck Reef site has been blocked ... By SNOW.
After multiple delays due initially to problems in obtaining authorization to drill from the South Africa Department of Mineral Resources, then, in the past two weeks, to conflicting territorial claims and protests by striking metal workers, our drilling finally got underway at 17:15 on Friday 15th July. In three working days we have obtained more than 120 m of core and completed the first hole, BARB1, at Tuesday midday. BARB1 intersected the 'tumulus' structure, an unusual komatiite flow in the Komati Formation at the Tjakastad site and several overlying komatiite flows. Preliminary logging has revealed wide variations in texture and composition in the lower part of the unit structures that were unsuspected in view of the relatively uniform olivine adcumulate rocks exposed at the surface. Present in the core, in addition to beautiful olivine adcumulates, are spectacular 'harrisitic' textures composed of enormous, highly skeletal olivine grains, a thick interval of olivine and pyroxene spinifex, an interval of highly amygdaloidal lava, and a totally unexpected zone of ultramafic hyaloclastite. The 'tumulus' unit is overlain by a series of thin, differentiated olivine spinifex komatiites. The rig on the Tjakastad site move on Tuesday night to BARB2 where we will drill a sequence of more normal flows of komatiite and komatiitic basalt. A second rig is expected to arrive later in the week and it will start drilling hole BARB3 either on the Middle Fig Tree site or on Buck Reef. The entire operation is supervised by our drilling manager, Gordon Chunnett, and his assistant Masi (his blog on our South African web site www.peeringintobarberton.com gives a detailed account of the events of the past week). Nick Arndt and Gary Byerly are site scientists for holes BARB 1 and 2; Mike Tice, Don Lowe, Christoph Heubeck and Axel Hofmann will supervise BARB3. Special thanks for assistance during the first stage of drilling are due to Prince Cambridge Dlamini, Elijah Lechela, Julius Mathebula, Fred Daniel, Richard Spoor and John Allen.
After about 10 months of frustration caused by major reorganization of the South African Department of Mineral Resources, we finally received the authorization to conduct our drilling program in the Barberton Belt. We have negotiated a new contract with the drilling company Buenti Drilling (Pty) Ltd and expect to conduct the drilling following the program outlined below. The core should be in the facilities of the Council for Geosciences in Pretoria in early September. We will then log it in detail and we will publish the descriptions on the ICDP web site around the end of the year. We will have a call-for-proposals to work on the core, which will be distributed to in early 2012. Priority will be given to scientists who have directly involved with the drilling itself or are from countries who have contributed to the costs of drilling.
The drilling project has been held up because of problems encountered in obtaining permissions to drill. We are hopeful that the document will be issued later this week and that drilling will start 1-2 days later. All five sites have been inspected by Gordon Chunnet (operations manager) members of the science teams and Dani Oberholzer, the manager from Geosearch the drilling contractor. At most sites representatives of the forestry companies were also present to assure that the sites complied with fire hazard regulations and other environmental factors.
