An update on scanning – post the workshop meeting scanning commenced. We are now busy with scanning of critical areas around the fault zone from various holes. On Tuesday, 18 September 2018, we concluded the scanning of the critical fault area of the mother hole (Hole A). We started scanning the branch hole (HOLE C). The scanning starts at 579.10 m depth, which is box number 5. This is a very critical section of scanning. As we think that the fault might have been intercepted by this branch hole.
Post drilling in deep South African gold mines, Moab Khotsong and Cooke 4 mine, ICDP-Dseis is holding a seminar meeting at the CSIR, Nelson Mandela Mining Precinct in South Africa. The meeting is attended by international scientists from Germany, Switzerland, Japan, USA and South Africa, and leading industry players such as Harmony gold, SRK and other major players. Many scientists are joining the meeting online. The meeting gives an update of the project and discusses core documentation and sampling strategy.
The second borehole 'Moab Hole B' is currently at 688 m depth. The drilled core is coming out in the triple tube barrel which prevents fragmented rock falling out of the barrel. In the forthcoming intersection of the fault zone, the fault material can be preserved. Today in the morning, Bennie Liebenberg and Michael Rickenbacher were cutting core samples for the planned analysis of thin section at ETH Zurich. In the afternoon, we continued logging and orienting the core at the core yard. Hopefully, tomorrow morning another 50 meters of core can be transported to the surface from the drill site at mine level 95 in a depth of 3000 meters below surface.
Drilling Seismologic Zones in Deep South African Gold Mines (DSEIS) - As part of skills transfer, intercontinental collaboration and progressive inclusion of young scientists in particular African women Ms Zamaswazi Nkosi, PhD student at the University of the Witwatersrand and researcher at Council for Scientific and Industrial Research (CSIR) attended the scanner training on Friday, 17/11/2017. She specializes in characterization of lithology and rock physical properties. The scanner training was conducted by Mr Siyanda Mngadi (Wits. University, South Africa) and Mr Kosuke Sugimura (Rits. University, Japan). This training lasted the whole day at CSIR, Center for Mining Innovation, Carlow Rd & Rustenburg Rd, Auckland Park. Zama will be analyzing and scanning Moab Khotshong’s gold mine core, which was drilled 2.9 km underground aimed at the heart of Mw 5.5 Orkney 2014 earthquake. This is a continuation of the work by both Mr Berset Nicolas (Swiss Federal Institute of Technology Zurich, Switzerland) and Rickenbacher Michael (Swiss Federal Institute of Technology Zurich, Switzerland).
Siyanda Mngadi, PhD student at the University of the Witwatersrand and Kosuke Sugimura, undergraduate student at the Ritsumeikan University are working with extremely fractured core, which makes it very difficult to scan. We are conducting a detailed fracture and lithological analysis. Unfortunately, this highly fractured core makes it almost impossible to orient because the individual core samples hardly match. It must be noted that this core was deliberately drilled into highly stresse, fractured zone and seismogenic around the stope for the purpose of analyzing shear fractures forming around the stope.
Siyanda Mngadi a student at the University of the Witwatersrand (left) and Kosuke Sugimura a student at Ritsumeikan University (right) are scanning Cooke 4 mine core samples from Site 7, Hole A. These core samples are highly fractured due to severe stress fracturing around the mining stopes. Ogasawara (2014) measured 127 MPa stress levels at Cooke 4. The triple tube drilling was used to preserve these fractures. The scanned images will be compared rigorously with OTV images.
Today, I trained Siyanda Mngadi on the ICDP core scanner. Meanwhile, the ICDP core scanner is packed again and ready for transportation to CSIR. There, Zama Nkosi is continueing with scanning Moab Hole A cores. Furthermore, the geophysical borehole logging had to be postponed, because the wireline winch broke down again. For fixing the wireline winch, it must be transported to surface again, which will take at least one week. In the later afternoon, Bennie Liebenberg and I had a Google hangout meeting with Dr. Tullis Onstott, Dr. Hiroshi Ogasawar and Dr. Martin Ziegler. An update of the current work on-site and the future Moab Hole B were discussed. Finally, today was my last working day and I will leave South Africa on Sunday. Back in Switzerland, I am going to conduct laboratory tests on the shipped core and I will still be part of the project. So it is time to say goodbye South Africa and goodbye dear DSeis-Members! I hope I see you again. Michael
Today, Ronald Conze updated the DIS for us from Germany and we can now work with newest version. Furthermore, Bennie Liebenberg and Michael Rickenbacher transported the core samples, which are 18 meters of NQ-bore core, to the airport. From there, the core samples are going to be shipped in the next two weeks two ETH Zurich in Switzerland. Finally, 100 new core boxes were delivered to Moab for the new bore core coming out of Moab Hole B. If everything goes smooth, drilling of the Moab Hole B will start in the next two weeks.
Today, Prof. Dr. Halil Yilmaz, Glen Nwaila, Zamaswazi Nkosi and Siyanda Mngadi from Wits University have visited Moab Khotsong gold mine. The purpose of the visit was to see the ongoing work on-site of the DSeis-project and to learn more about the ICDP-core scanner. Akimasa Ishida and Kosuke Sugimura could do a demonstration of the DCDA instrument and Michael Rickenbacher has introduced the Wits-student into core scanning. Furthermore, the wireline winch was delivered to site 1 and the first borehole was flushed with water. Hence, the geophysical borehole logging can start tomorrow with the optical and acoustic televiewer.
The LM 90 Drill Rig was dismantled last week, to allow to construct plin for Hole B. Then, digging out of foot wall was undertaken to construct plin for hole B. Yesterday a Mine Surveyor surveyed in a new line direction for Hole B (10° left of Hole A). Furthermore, Michael packed all the core samples and the samples are now ready to get shipped Zurich.
Kosuke, Akimasa and Michael made new core box photos for box 1-39 and uploaded the photos into the DIS. Furthermore, the team continued with scanning the core and preparing the core sampling. Underground at site 1, the drilling machine got dismantled and moved by 10 degrees. Therefore, drilling of the second borehole at site 1 could start soon. At site 2, the miners are still blasting a cubby and preparing the site for the third borehole.
Kosuke, Akimasa and Michael made new core box photos for box 1-39 and uploaded the photos into the DIS. Furthermore, the team continued with scanning the core and preparing the core sampling. Underground at site 1, the drilling machine got dismantled and moved by 10 degrees. Therefore, drilling of the second borehole at site 1 could start soon. At site 2, the miners are still blasting a cubby and preparing the site for the third borehole.
Akimasa and Kosuke tested different rock types with their DCDA instrument like siltstone, intrusive and quartzite. Michael continued with core scanning and prepared the core sampling.
Today, Akimasa Ishida and Kosuke Sugiumra tested the Babrosco-Quartzite and Crown Lava with their DCDA instrument. Michael Rickenbacher scanned 8 different core sections which will be later shipped to ETH Zurich and tested in the laboratory. The goal of testing core in the lab is to retrieve relevant geological and geotechnical parameters about the host rock of the Orkney-earthquake.
The drilling machine is now unrigged and dismantled. Meanwhile, the drilling crew is now digging a hole for the new concrete block. As soon as the concrete block has finished, the drill machine will be mounted on it and drilling could start again for the Moab Hole B at site 1. The new borehole will be swung by 10 degrees with respect to the first borehole.
Today, Akimasa Ishida conducted the first DCDA measurements. Meanwhile, Kosuke Sugimura continued with scanning the cores. Bennie Liebenberg and Michael Rickenbacher were busy with orienting the core and doing the fracture log.
During a first look at the latest core boxes, the contact zone between the intrusive and the quartzite was studied. The contact is generally sharp and full of calcite and quarz veins. Unfortunately, the contact zone does not exhibit any fresh fractures and cracks and therefore, the contact zone was not reactivated during the M5.5 earthquake. Furthermore, Michael Rickenbacher and Kosuke Sugimura started to scan the bore core with the ICDP-core scanner.
Today, the latest core boxes were delivered to the surface. In it is the bore core from 760-817 meters. At meter 801.8, a sharp contact between the intrusive and the following cross-bedded quartzites was found. The 10cm-thick contact exhibited intact, old calcite veins which had not been reactivated by the Orkney earthquake. Apparantely, the intrusive (734-802m) in this borehole section does not host the fault zone of the Orkney earthquake. Furthermore, Akimasa Ishida (MSc student from Ritsumeikan University) and Kosuke Sugimura (BSc student from Ritsumeikan University) arrived safely in South Africa. With them is the DCDA system, which will allow them to recalculate stress ratios from bore core diameters.
The borehole extension of another 57 meters to a depth of 817 meter has now completed. In the next few days, the latest core boxes will be delivered to the surface and then logged. Today, Akimasa and Kosuke from Japan arrived here in South Africa.
The Drilling going on 817 m. 760-817 m core is still under ground. 0-760 m core information was uploaded on Drilling Information System.The Drilling going on 817 m. 760-817 m core is still under ground. 0-760 m core information was uploaded on Drilling Information System.
The drill crew started to extend the first borehole for 60 more meters. Yesterday, 15 meters were drilled and the hopefully the core boxes will be brought to the surface soon. Furthermore, Tatsunari Yasutomi anlayzed the hydrophone data and he found some seismic events nearby the borehole. Therefore, the seismic signal could originate from the seismic zone of the Orkney earthquake.
Today Tatsuanri Yasutomi went underground to get retrieve the hydrophone data. From Friday until Monday, the hydrophone recorded seismic events on level 95 e.g. aftershocks and mine blastings. Furthermore, it was decided by the Dseis-Member to extend the first borehole with 60 more meters. Hopefully, the nearby seismogenic zone of the Orkney earthquake can then be intersected.
After the visit of site 1 & 2 on level 95 last week, the DSeis-member decided to drill the second borehole from site 1. Therefore, the drilling machine has only to be swung of a certain angle to start with Moab Hole B. Furthermore, Michael Rickenbacher is busy with conducting the fracture log of the borecore of Hole A. Many fractures like calcite veins and shear displacements are measured in great detail.
Today, Michael Rickenbacher assembled the core scanner at the core yard. The core scanner will be used to create unrolled 360 degree images of interesting sections of the 760 meter long bore core. Of major interest are for example cataclasites and earthquake-related fractures.
Yesterday evening, Dr. Tulli C. Onstott from Princeton University arrived in South Africa. Already this morning Dr. Tulli C. Onstott, Dr. Hiroshi Ogasawara, Dr. Jan G. Vermeulen, Dr. Errol Cason, Tatsunari Yasumoti and Michael Rickenbacher went underground to visit site 1 and 2. At site 1, where the Moab Hole A was drilled, Dr. Hiroshi Ogasawara could test the hydrophone in the 760 meter deep borehole. The hydrophone is able to detect micro-seismicity (aftershocks) of the Orkney earthquake fault zone, which will be then analyzed by Tatsunari Yasumoti. The hydrophone test could help to detect the exact position of the fault zone. Furthermore, the DSeis-member could visit site 2 and on the way Dr. Tulli C. Onstott, Dr. Jan G. Vermeulen and Dr. Errol Cason, which are interest in deep microbiological life, could probe water of an underground spring located at an intersecting dyke. Back to surface again, Michael Rickenbacher could fetch the ICDP-core scanner which was shipped from the GeoForschungsZentrum Potsdam (GFZ) in Germany. The core scanner will be used to generate unrolled 360 degree images of the 760-meter long bore core from Moab Hole A.
Today on the surface, Michael continued with the fracture log. The core quality is excellent and exhibit some natural mineralized fractures. Sometimes small shear zones like cataclasites or ultracataclasites can be observed. In the underground, it was planned to test the hydrophone in Moab Hole A in order assure that the instruments are working for the main test phase. Unfortunately, a fuse was broken in the current transformer which powers the wireline winch. During the next night shift, a new fuse for the current transformer will be delivered. Hopefully, the main test phase of the hydrophone over the weekend can then be conducted without any problems. Finally, it was confirmed that the core scanner will arrive tomorrow. With the core scanner, unrolled pictures of the 760 meter long borecore will be undertaken.
The wireline winch which is used for lowering down the hydrophone and the instruments for the geophysical borehole logging has arrived the drilling site on level 95. Furthermore, Dr. Hiroshi Ogasawara will take the hydrophone underground tomorrow, hence the hydrophone tests can be undertaken this week. On surface, Michael has finished the subdivision of core runs and core sections and he is now busy to tip the data into the Drilling Information System (DIS).
Yesterday, Taku Noda left Moab Khotsong gold mine to join a training in Wits, Johannesburg. Furthermore, Michael Rickenbacher started with the fracture log of the 760 meter long bore core of Moab Hole A. Meanwhile, Dr. Hiroshi Ogasawara arrived here on-site and he is now organizing the forthcoming hydrophone test in Moab Hole A in order to localize the nearby fault zone of the M5.5 earthquake. Unfortunately, the Gyro-survey revealed that the borehole has deflected in direction of the bedding plane and thus, the borehole is apparently running parallel to the fault zone. However, the planned geophysical borehole logging, the hydrophone installation and the fracture log of the bore core could provide necessary information about the nearby fault zone which will also be included for the forthcoming decision of position and orientation of the second borehole. Last but not least, the latest core boxes with cores until 760 meters arrived at the surface today.
Today, Dr. Hiroshi Ogasawara and Dr. Kato visited the Moab Khotsong gold mine. With them, a hydrophone was brought to the site. The hydrophone is packed in a 2 meter long tube and it will record P-wave and S-wave arrivals of the seismogenic zone of the Orkney earthquake in the Moab borehole A. The plan is to lower down the hydrophone over the weekends and to analyze the seismic record afterwards to localize the exact position of the active fault zone.
Today, a Gyro-survey was undertaken to measure the borehole orientation of Moab Hole A. The Gyro-survey results will be available on Monday. Furthermore, a new wireline winch for the geophysical borehole logging was delivered to Moab Khotsong gold mine. During the next days, the wireline winch will be transported to mine level 95. Then, the miners started to blast the second drill site for the Moab Hole B. In the next few weeks, the DSeis-members are going to decide where and when the second borehole will be drilled. Finally, Tatsunari Yasutomi was introduced into the core logging activities at the core yard and he has now started to upload data into the Drilling Information System.
This afternoon, Tatsunari Yasutomi arrived here in South Africa. He is a MSc student from Kyoto University, Japan and he is going to support the core logging of the 760 meters long bore core of Moab Hole A. Tomorrow, he will be introduced into the mine and into the ongoing work here on-site.
In the last few days, the bore core was subdivided into core runs and core sections from meters 100 to 320. At the same time, photos are taken for each core box and then, uploaded to the Drilling Information System. The definition of core runs and sections is the basis for the later lithology- and fracture log, which is going to be started in the next few days.
:) Today, the drilling crew has accomplished the drilling of the 760-meter-deep borehole at Moab Khotsong Hole A on mine level 95! Since the latest core boxes are still underground, no evidences of the nearby seismogenic zone can be reported at this stage. However, the following core logging and the planned geophysical borehole logging next week could reveal new insight into the Orkney earthquake.
Today, the drilling crew has accomplished the drilling of the 760-meter-deep borehole at Moab Khotsong Hole A on mine level 95! Since the latest core boxes are still underground, no evidences of the nearby seismogenic zone can be reported at this stage. However, the following core logging and the planned geophysical borehole logging next week could reveal new insight into the Orkney earthquake.
Today, the drilling crew has accomplished the drilling of the 760-meter-deep borehole at Moab Khotsong Hole A on mine level 95! Since the latest core boxes are still underground, no evidences of the nearby seismogenic zone can be reported at this stage. However, the following core logging and the planned geophysical borehole logging next week could reveal new insight into the Orkney earthquake.
After the inner core barrel tube got stuck inside the rod on Wednesday, the drill team had to pull out the rods for several hundred meters during the last two days. Unfortunately, the wireline had to be cut for each rod segment. Today, the drill team could retrieve the inner core barrel tube out of the rods and a new wireline was delivered to the drilling site at level 95, 2900 meters below earth surface. Presumably on Monday, drilling will continue for the last 15 meters. Afterwards, probably until end of next week, the extensive geophysical borehole logging can start and provide more insights into the nearby seismogenic zone of the Orkney earthquake.
Currently, the drilling is in the Babrosco formation which consists of cross-bedded, stripped and massive quarzites. With an advance of the drilling, a conglomerate basis in contact with the Rietkuil formation is expected. Today, no drilling could be undertaken, because of a technical problem with the inner tube core barrel. Probably tomorrow the drilling can continue and reach a depth of 760 meters, which will be the end of the borehole.
After the today's drilling shift, the drilling advanced to a depth of 745 meters. At this stage, the borehole has not yet intersected the seismogenic zone of the Orkney earthquake from 2014. Untill now, no earthquake related fractures could be recognized on the drilled core. The drilling during the next few days and the following geophysical borehole logging are going to give more information about the probable fault zone of the Orkney earthquake.
The drilling has progressed to a depth of 745 meters. In the next week the drilling is going to stop and the geophysical borhole logging is going to be undertaken. Today, Taku Noda and Michael Rickenbacher did the inventory list for the first 100 meters of core.
The drilling of the deep borehole at Moab Khotsong has now advanced to a depth of 730 meters. We checked the drilling site on level 95 in a depth of 2900m and the latest cores.
The drilling of the deep borehole of Moab Khotsong now advenced to a depth of 712m. Micheal checked the latest core because the drilling is getting closer to the fault.
The drilling of the deep borehole at Moab Khotsong has now advanced to a depth of 697 meters. With a drilling rate of 15 meters a day, the end of the borehole at 750 meters depth and the fault zone are probably intersected next week. Last week Taku Noda from Rits University and Michael Rickenbacher from ETH Zurich arrived in South Africa. During the next weeks, Taku and Michael are going to start with core logging from 180 meters.
Set up of one or the probes for downhole logging in the 186 meters deep borehole A. The probes used are the following: 3-arm caliper, dual density, full wave form sonic, OTV and ATV.
153 meters of core are now available the core yard. Core logging is in progress. The cores are marked accordingly to the ICDP standard; blue line on the left, red line on the right.
Nicolas is working on core logging. A core orientation tool gives the "bottom line" of the core, which is useful to derive true geographic orientation of discontinuities observed in the cores.
84 meters were transported to surface on Thursday 15th of June. Cores are now laying on the core yard waiting for core logging. The lithology is slate (from shale and siltstone). No intrusive and no faults are observed so far.
Dseis Team uses a core orientation kit to obtain orientation of the core. A special tool containing accelerometers is added at the top of the core barrel with the aim to record position of the core barrel in space. Once the barrel retrieved out of the hole, drilling operators can reorient the core accordingly to the indication from the tool. The 3 meters drill run is marked at its bottom with a wax crayon as shown by the picture.
