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< July/August
IODP Expedition 352
Izu-Bonin-Mariana Forearc
Daily Science Report for 28 September 2014
LOCATION: Passenger Terminal Berth E4, Keelung, Taiwan
SCIENCE UPDATE: The science party finalized the Expedition Summary. A short meeting was held to celebrate the successful completion of Expedition 352. The JOIDES Resolution arrived in Keelung, with the first line thrown ashore at 1536 h. The scientists and technical staff are scheduled to depart the vessel tomorrow.
Daily Science Report for 27 September 2014
LOCATION: In transit to Keelung, Taiwan
SCIENCE UPDATE: A meeting was held to discuss the shore-based processing and distribution of community samples that will be shared among several investigators. Scientists finalized all site reports and continued to work on the Expedition Summary.
Daily Science Report for 26 September 2014
LOCATION: In transit to Keelung, Taiwan
SCIENCE UPDATE: A science meeting was held to discuss the Site U1442 physical properties and downhole logging results. Scientists continued to work on site reports and the Expedition Summary.
Daily Science Report for 25 September 2014
LOCATION: In transit to Keelung, Taiwan
SCIENCE UPDATE: Today, samples were collected from Hole U1442A cores for postcruise research. During Expedition 352, a total of 5515 samples have been taken for shipboard analyses and postcruise research.
A science meeting was held to discuss the Site U1442 structural geology and paleomagnetic results, and scientists continued to work on reports.
Daily Science Report for 24 September 2014
LOCATION: In transit to Keelung, Taiwan
SCIENCE UPDATE: Logging operations were completed at 0115 h. The drill string was pulled to the surface, clearing the rig floor at 0225 h. The seafloor positioning beacon was retrieved at 0940 h and the hydrophones and thrusters were raised. The vessel got underway for Keelung at 1030 h, averaging 12 kt for the remainder of the day.
A science meeting was held to discuss the Site U1442 petrology results.
Scientists submitted tentative postcruise manuscript titles and continued to work on Site U1442 reports.
Scientists started selecting the samples that will be taken from Hole U1442A cores for postcruise research.
Daily Science Report for 23 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: In preparation for logging, the early part of the day was spent conditioning the hole to the total cored depth of 529.8 mbsf. The RCB bit was released in the hole at 0845 h, and the end of the drill string was raised to 97 mbsf. Logging operations started at 1030 h with the assembly of the triple combo-magnetic susceptibility sonde (MSS) tool string. Two passes were completed to 379 and 305 mbsf, respectively, between 1100 and 1815 h. The Formation MicroScanner (FMS)-sonic tool string was assembled next. Two passes were completed to 287 mbsf between 1815 h and 2400 h.
Core U1442A-57R consists of massive dark gray-green lava that varies from aphyric to moderately plagioclase-phyric. Plagioclase typically forms small glomerocrysts as well as single phenocrysts. These lavas are highly brecciated by several shear zones, and much of the recovered core consists of gravel-sized rubble.
A science meeting was held to discuss the Site U1442 sedimentology, biostratigraphy, and geochemistry results.
Daily Science Report for 22 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-54R to 57R penetrated from 490.8 to 529.8 mbsf and recovered 9.2 m (24%). The last core of Site U1442 arrived on deck at 2350 h. At the end of the day, preparations started for logging Hole U1442A. After logging, we will depart for Keelung on 24 September.
Cores U1442A-51R to 56R consist of boninites and aphyric or sparsely phyric basalts. Cores 51R–53R include lighter colored flows that intrude hyaloclastites, similar to Unit 8 in Hole U1439C. Below that, there are massive aphyric lavas that are highly brecciated.
Daily Science Report for 21 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-47R to 53R penetrated from 422.6 to 490.8 mbsf and recovered 8.5 m (12%).
Cores U1442A-45R to 51R consist of boninites and aphyric or sparsely phyric basalts. This interval appears to be mixed magmatically, with lighter colored flows intruding hyaloclastites before lithification. The overall appearance is similar to Unit 8 in Hole U1439C.
A science meeting was held to discuss end-of-expedition and post-expedition activities and obligations.
Daily Science Report for 20 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: The RCB bit was changed and the drill string was lowered back down to the seafloor. The camera was sent down to observe the reentry into the free-fall funnel, and Hole U1442A was reentered at 1105 h. The drill bit reached the previous coring depth at 1700 h, after clearing obstructions in the hole at 82 and 279 mbsf. Cores U1442A-45R to 46R penetrated from 403.1 to 422.6 mbsf and recovered 0.7 m (4%).
Work continued on the classification of the Hole U1442A igneous rocks. Preliminary unit boundaries were defined through Core U1442A-44R.
A science meeting was held to discuss the content and submission guidelines of abstracts and manuscripts submitted within the moratorium.
Daily Science Report for 19 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-41R to 44R penetrated from 364.0 to 403.1 mbsf and recovered 2.5 m (6%). In preparation for changing the RCB bit, a free-fall funnel (FFF) was assembled in the moonpool and dropped at 1510 h. The camera was sent to the seafloor to observe the FFF and the drill string pulling out of the hole. The bit had reached 122 m below rig floor by midnight.
Cores U1442A-39R to 44R consist of boninites and aphyric or sparsely phyric basalts. Some pieces appear to represent dikes intruded into the volcanic section, with aphanitic textures and no vesicles. Volcanic fragments are common. There are no obvious breaks in chemistry or petrography.
A science meeting was held to discuss the Site U1441 geochemistry results.
Daily Science Report for 18 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-35R to 40R penetrated from 305.5 to 364.0 mbsf and recovered 5.5 m (9%). A precautionary wiper trip was conducted from 100 to 344.6 mbsf and no fill was found at the bottom of the hole.
Cores U1442A-30R to 38R consist of massive lavas, with some possible pillows. Boninites with abundant phenocrysts and aphyric or sparsely-phyric basalts are found throughout this section. There are no obvious breaks in chemistry or petrography. Some pieces appear to represent dikes intruded into the volcanic section; they are compositionally distinct from the rocks around them, with no vesicles or phenocrysts, and the aphanitic cryptocrystalline textures that are common in shallow dikes.
A science meeting was held to discuss the Site U1441 paleomagnetism and physical properties results.
Samples were collected from Hole U1441A cores for postcruise research.
Daily Science Report for 17 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-27R to 34R penetrated from 227.6 to 305.5 mbsf and recovered 13.5 m (17%).
Cores U1442A-20R to 29R consist of hyaloclastite breccia, containing rounded lava globules from about 1 cm up to several centimeters across, in a matrix of green, altered glass ash, along with more angular fragments. Glass fragments are common, most of them completely unaltered. This unit is over 137 m thick (from 111 to 248 mbsf), terminated by a major fault zone at the top of Section U1442A-29R-2. Below the fault zone are massive lavas, commonly brecciated near the contact.
Cores U1442A-27R to 30R contain 28 structures. The main features include carbonate and zeolite veins that tend to form conjugate sets with a steep to nearly vertical bisecting plane. A few microbreccias were observed at 238 and 247 mbsf. A 40 cm thick shear zone with steep dip occurs at 248 mbsf. This zone is characterized by an abundance of gelatinous material that seems to ooze out of zeolite.
A science meeting was held to discuss the Site U1441 petrology and structural geology results.
Scientists started selecting the samples that will be taken from Hole U1441A cores for postcruise research.
Daily Science Report for 16 September 2014
LOCATION: Hole U1442A (28°24.5784′N, 142°37.3368′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-19R to 26R penetrated from 149.9 to 227.6 mbsf and recovered 10.6 m (14%).
Core U1442A-7R reflects a change in sedimentation and consists of alternating layers of consolidated clay, varying from dark brownish up to brownish black (manganese banding) to pinkish gray. After Core 7R, the sedimentation returns to olive- and pale-colored, structureless nannofossil ooze with conspicuous bioturbation and different amounts of silt and sand. The sediment becomes lithified toward the base of the hole in Cores 9R and 10R, and former parallel bedding planes are tilted up to 35°. The top of the igneous basement in Core 10R includes five main clasts of altered extrusive igneous rocks that are subrounded and coated with manganese oxide. The clasts are supported within a matrix of pinkish colored, non-calcareous silty clay.
Section U1442A-10R-3 through Core 12R consist of volcanic breccia, with angular fragments in an altered glass matrix. Cores 13R–20R consist of ~90 m of hyaloclastite breccia, containing rounded lava globules from ~1 cm up to several centimeters across, in a matrix of green, altered glass ash, along with more angular fragments. Glass fragments are common, many of them completely unaltered.
Cores 10R to 24R contain few structural features in comparison with previous holes. The key structures include thin, subvertical tension fractures filled with zeolite and calcite. One piece in Core 24R contains a prominent planar fabric provisionally interpreted as flow banding in basaltic lava or rheomorphic flow in a tuff.
A science meeting was held to discuss the Site U1441 sedimentology and biostratigraphy results.
Daily Science Report for 15 September 2014
LOCATION: Hole U1442A (28°24.58′N, 142°37.34′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1442A-2R to 18R penetrated from 4.0 to 149.9 mbsf and recovered 44.4 m (30%).
In general, primary sedimentary structures have been strongly disturbed by rotary drilling. The sediment in Cores U1442A-1R to 5R is mostly pale beige to pale brown silty to sandy nannofossil mud and nannofossil ooze. The sediment becomes slightly darker and more muddy to the base of this interval, and the calcareous nannofossils decrease in the lowermost part of Core 6R. Dark gray patches are interpreted as the remains of admixed thin ash layers dispersed by bioturbation, reworking, and/or drilling disturbance. Sediment bedding is subhorizontal down to Section U1442A-9R-2 and becomes inclined at the bottom of the sedimentary section.
Sediments containing calcareous nannofossils were recovered from core catcher Samples U1442A-1R-CC to 9R-CC. An additional sample was taken from Section 10R-2, 22–23 cm, just above the layer containing igneous rocks. A fairly continuous condensed section was recovered with sediments from the Eocene/Oligocene boundary up to as recent as the Late Pleistocene.
Daily Science Report for 14 September 2014
LOCATION: Hole U1441A (28°25.6379′N, 142°43.5390′E, 4447 m water depth; proposed Site BON-6A);
Hole U1442A (28°24.58′N, 142°37.34′E, 3162 m water depth; proposed Site BON-5A)
SCIENCE UPDATE: Cores U1441A-21R to 22R penetrated from 189.9 to 205.7 mbsf and recovered 0.8 m (5%). Given the igneous rock types already recovered, the poor recovery, and worsening hole conditions, the decision was made to terminate Site U1441 and move to Site U1442 (proposed Site BON-5A). The drill string was raised while the ship moved to Site U1442. The drill string cleared the rig floor at 1450 h, ending Hole U1441A. The bottom-hole assembly was made up with a new RCB bit and lowered to the seafloor. Hole U1442A was spudded at 2320 h. Core U1442A-1R penetrated from 0 to 4.0 mbsf and recovered 5.7 m (141%).
Cores U1441A-17R, 18R, and 20R–22R consist of light gray, aphanitic basalt, with rare microphenocrysts of plagioclase. One piece has a chilled margin and a coating of unaltered glass, suggesting that this unit may be a pillow lava. Core 19R contains a similar, light gray, aphanitic basalt with 3% clinopyroxene phenocrysts. All of the basalts at this site are forearc basalts similar to those recovered at Site U1440.
The last set of Hole U1439C samples were collected for postcruise research.
A science meeting was held to discuss the Hole U1439C logging results and the move to Site U1442 (BON-5A).
Daily Science Report for 13 September 2014
LOCATION: Hole U1441A (28°25.6379′N, 142°43.5390′E, 4447 m water depth; proposed Site BON-6A)
SCIENCE UPDATE: Cores U1441A-15R to 20R penetrated from 131.5 to 189.9 mbsf and recovered 5.9 m (10%). A wiper trip was conducted from 82 to 187 mbsf and 2.7 m of fill was cleaned from the bottom of the hole. Coring resumed at 2200 h.
Cores U1441A-10R and 13R–16R contain a homolithic breccia deposit that is well cemented in Cores 14R–16R and composed of angular to subrounded volcanic clasts in a matrix of coarse volcanic sand. All of the lava clasts are likely from the same flow or source. Large, coarser grained clasts are found in the upper parts of Core 10R. Below that fine-grained to aphanitic volcanic clasts dominate. The coarser grained clasts have diktytaxitic textures and rare pipe vesicles. The fine-grained to aphanitic volcanic clasts are characterized by segregation pipe vesicles up to several centimeters long, and commonly retain portions of their chilled or glassy margins, showing that they originate from a pillow lava flow. The segregation vesicles are filled with a frothy glass, probably formed by continued outgassing of the late stage intra-telluric melt from the crystalline portion of the rock. Pipe vesicle orientations within individual clasts are subparallel, but their orientations vary widely between pieces, indicating that these are in fact clasts and not an intact lava flow. This is consistent with the recovery of well-cemented breccia in Cores U1441A-13R and 14R. The Hole U1441A rocks are interpreted to represent a mass wasting deposit.
Scientists started selecting the third and final set of samples to be taken from Hole U1439C for postcruise research.
A science meeting was held to discuss Hole U1439C geochemical, physical properties, and paleomagnetic results.
Daily Science Report for 12 September 2014
LOCATION: Hole U1441A (28°25.6379′N, 142°43.5390′E, 4447 m water depth; proposed Site BON-6A)
SCIENCE UPDATE: Cores U1441A-2R to 14R penetrated from 5.0 to 131.5 mbsf and recovered 42.6 m (34%). Hard rock was recovered in Core 10R. Cores 11R and 12R had zero recovery, which was attributed to a plugged bit. A deplugger was sent down to remove whatever was clogging the bit and coring resumed.
Cores U1441A-1R to 4R contain pale brown silty nannofossil ooze with four discrete ash layers, followed by a muddy volcanic breccia-conglomerate interbedded by some volcaniclastic sand layers to a depth of 24 mbsf. In Cores U1441A-5R to 9R, the sediment is dominated by brown to greenish gray silty mud, partly enriched in silicic microfossils and occasional ash layers.
Nine core catcher samples were examined for microfossils. Nannofossils in Samples 1R-CC and 2R-CC yield an approximate Late Pleistocene age, whereas Sample 5R-CC yields an approximately late Miocene age (5.59–8.12 Ma).
The majority of primary sedimentary structures in Cores U1441A-1R to 9R are severely disturbed by RCB drilling deformation. Only five bedding planes were observed in sections where the sediment was more competent. The general bedding attitude is horizontal.
A science meeting was held to discuss Hole U1439C petrology and structural geology results.
Daily Science Report for 11 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A);
Hole U1441A (28°25.64′N, 142°43.54′E, 4447 m water depth; proposed Site BON-6A)
SCIENCE UPDATE: Today we completed wireling logging in Hole U1439C. Two passes were made with the Formation MicroScanner (FMS)-sonic tool string down to ~400 mbsf, and the tools were rigged down by 0530 h. The drill string was recovered while moving the ship to Site U1441 (alternate Site BON-6A) in dynamic positioning mode. The end of the drill string arrived on the rig floor at 1105 h, ending Hole U1439C.
A rotary core barrel (RCB) bottom-hole assembly was made up with a C-4 RCB bit, and the drill string was lowered back down to the seafloor. The drill bit reached the seafloor at 2200 h, and Hole U1441A was spudded at 2245 h. Core U1441A-1R penetrated from 0 to 5.0 mbsf and recovered 1.4 m (28%).
We started collecting the second set of Hole U1439C samples intended for postcruise research.
Daily Science Report for 10 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: The hole was cleaned from 437 to 533 mbsf (10 m from the bottom of the hole) between 0000 h and 0700 h. The tri-cone bit was released inside the hole and the end of the drill string was set to 150 mbsf, inside the casing. The triple combo tool string with the magnetic susceptibility sonde at the end was rigged up at 1200 h and two passes were completed down to ~402 mbsf. Next, the Formation MicroScanner (FMS)-sonic tool string was rigged up at 2100 h and run into the hole. Once logging is completed, we will move to Site U1441 (alternate Site BON-6A).
Scientists started selecting the second set of samples to be taken from Hole U1439C for postcruise research.
Daily Science Report for 9 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Sea conditions were bad throughout the day due to the proximity of Tropical Storm Fengshen. In preparation for logging, the drill string was lowered to the seafloor, but we had to wait for the weather to improve (0515 to 1330 h) before we could deploy the camera system for reentry. After 15 min of maneuvering the ship for reentry, Hole U1439C was reentered at 1530 h and the camera was retrieved. Our next step is to clean the hole as deep as possible for the logging tool strings (RCB coring had reached a total depth of 554.3 mbsf). The drill string with a tri-cone bit had reached 437 mbsf by midnight.
A meeting was held to review the igneous units at Hole U1439C, primarily in the middle portion of the hole that we are preparing to sample for postcruise research.
Daily Science Report for 8 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Core U1439C-45R penetrated from 540.8 to 544.3 mbsf and recovered 1.3 m (38%). Core 46G was recovered from 532.0 to 539.0 mbsf while trying to clean up fill that had accumulated at the bottom of the hole. As a result of the deteriorating hole conditions, we decided to raise the drill string to examine the bit and to change it to one more appropriate for harder formations. While trying to raise the drill string we lost rotation and circulation, and the bottom-hole assembly (BHA) got stuck. Several hours were spent trying to free it, and it was eventually freed by applying 190,000 lb of force.
The scientists held a meeting to discuss what would be the best use of the time remaining in the expedition. We decided to end coring at Hole U1439C, log the hole as deep as possible, and then move to alternate Site BON-6A to investigate the volcanic stratigraphy between Sites U1439 and U1440. The rest of the day was spent raising the drill string to the surface and making up a BHA with a tri-cone bit and a mechanical bit release in preparation for logging.
Cores U1439C-44R and 45R contain aphyric, fine-grained basalt or dolerite, with modal plagioclase in the groundmass and sparse phenocrysts of augite. The rocks have a greenish tinge from incipient sausserization of plagioclase, and dark clots that may be chlorite overgrowths. There is only one piece in either core that appears volcanic (Core U1439C-44R, Piece 11); all other pieces in both cores are fine grained to microcrystalline, with granular or doleritic textures. Chilled margins are found in some pieces, suggesting that these are dike rocks.
Cores 41R to 44R penetrated a normal fault zone with steeply inclined slickensides and weakly cohesive to incohesive cataclasites.
We are preparing to collect the next batch of Hole U1439C samples intended for postcruise research.
The sea state got increasingly worse toward the end of the day with the approach of Tropical Storm Fengshen, which is passing ~400 km to the north of us.
Daily Science Report for 7 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Cores U1439C-41R to 44R penetrated from 514.1 to 540.8 mbsf and recovered 6.2 m (23%).
Cores U1439C-38R to 43R contain aphyric microcrystalline basalt, with modal plagioclase in the groundmass and sparse microphenocrysts of olivine. Pillow lava dominates in the shallower sections, but massive dark gray to black basalt becomes dominant downhole. Chilled margins are found in some massive basalt fragments, suggesting that many of these massive units are dike rocks. One probable dike has a composition similar to lavas higher in the section. Fault rocks are common in Cores 41R to 43R, including breccia and sheared phaccoidal fragments with polished chlorite ± serpentine surfaces.
ICP measurements of samples from Sections U1439C-19R-1 to 31R-5 show that some lavas have basaltic major element compositions.
Cores U1439C-39R to 42R contain 37 structures. These structures consist mostly of carbonate veins and fracture planes with prominent slickensides. The sense of slip determined on oriented pieces is both normal and reverse. Thin sections reveal vein microstuctures in calcite, such as thin twins and subgrain boundaries, indicative of relatively low strain and low strain rate. Core 43R is highly fractured, with abundant slickensides, indicating the presence of a major fault in this interval.
Magnetic susceptibility values show a large increase at 480 mbsf (Core U1439C-36R).
Samples intended for postcruise research were collected from Cores U1439A-20X to 21X and U1439C-2R to 20R.
Daily Science Report for 6 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Cores U1439C-35R to 40R penetrated from 465.3 to 514.1 mbsf and recovered 16.3 m (33%).
Cores U1439C-34R to 36R contain aphyric to moderately phyric boninite pillow lava. From the bottom of Core 36R and continuing through Core 38R, the lavas are all aphyric basalts, with modal plagioclase in the groundmass and rare microphenocrysts of olivine. Pillow lava dominates, but some lavas are massive. This represents a major lithologic transition.
Portable XRF chemostratigraphy measurements show that domains with high and low Cr are intermingled in Cores 35R–38R.
Cores 36R–38R contain slickensides and incohesive fault gouge, indicating the presence of a fault zone.
The Sample Allocation Committee reviewed the samples requested for postcruise research.
Daily Science Report for 5 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Hole U1439C was reentered for the third time at 0315 h and the camera system was retrieved at 0515 h. While the drill string was being lowered to the previous coring depth, material fell in from above and it took from 0600 h until 1200 h before the drill string could be freed. The drill string was raised all the way to the end of the casing and the hole was swept with mud and cleaned between 178 and 465 mbsf. Core U1439C-34G was recovered during this process, and coring resumed at 465 mbsf with Core 35R.
Core U1439C-33R contains the same purple-gray aphyric to moderately-phyric boninite pillow lava that comprises Unit 7.
A meeting was held to review sample needs for postcruise research, and sample selection started at 1800 h.
Daily Science Report for 4 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Cores U1439C-32R to 33R penetrated from 445.8 to 465.3 mbsf and recovered 8.0 m (41%). Following the recovery of Core 33R, the drill string was raised to the surface to change the bit. The drill string was lowered back down to the seafloor, and at midnight the camera system was on its way to the seafloor for the next reentry.
Cores U1439C-31R to 32R contain the same purple-gray aphyric to moderately-phyric boninite pillow lava encountered previously. Small- to medium-sized pillows dominate, with less common interpillow breccias and hyaloclastite. The petrology group continued to refine the lithostratigraphy, resulting in seven igneous units.
Preparations continued for another round of selecting samples for postcruise research.
Daily Science Report for 3 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Cores U1439C-28R to 31R penetrated from 406.8 to 445.8 mbsf and recovered 19.3 m (49%).
Cores U1439C-24R to 30R contain the same purple-gray aphyric to moderately phyric boninite pillow lava encountered in Cores 14R–23R. In many places it appears that the highly phyric lavas represent the cumulus-enriched lower portions of large pillow lavas; the upper portions and small pillows are commonly aphyric or sparsely phyric. Based on the review of Cores 2R–30R, along with newly available ICP and pXRF data, the lithostratigraphy has been refined to six units. The thickest unit extends from ~250 to at least 442 mbsf.
Cores U1439C-26R to 29R contain 66 structures. The dominant type of structures are carbonate-rich tension veins up to 5 mm in width. Slickensides have been observed and suggest proximity to a fault between 375 and 400 mbsf. A few centimeter-wide cataclastic zones and shear zones also occur in this interval.
The science party started preparing for another round of selecting samples for postcruise research.
Daily Science Report for 2 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: Cores U1439C-23R to 27R penetrated from 358.1 to 406.8 mbsf and recovered 11.3 m (23%).
Cores U1439C-21R to 23R contain the same purple-gray aphyric to sparsely-phyric boninite pillow lava encountered in Cores 14R–20R, along with highly olivine-phyric boninite pillow lavas. A review of Cores U1439C-2R to 20R, along with all of the thin sections for these cores, suggests that there are eight informal lithostratigraphic units at this point.
The lithostratigraphic units are based on the physical volcanology of the units (pillows, sheet flows, hyaloclastite breccias) and their phenocryst assemblages, supplemented by pXRF measurements. Unit thicknesses range from ~2 m to >80 m. All of the units are boninite (olivine and/or orthopyroxene phyric), but one unit is relatively evolved, with plagioclase and augite as phenocrysts. We expect these informal unit designations to evolve as we obtain more core.
Cores U1439C-24R to 25R contain pieces with slickensides and fine-grained cataclasite, indicating the presence of a fault zone.
Daily Science Report for 1 September 2014
LOCATION: Hole U1439C (28°24.4491′N, 142°36.5368′E, 3129 m water depth; proposed Site BON-2A)
SCIENCE UPDATE: When the drill string reached the seafloor at 0430 h and the subsea camera was deployed for reentry, we observed that the fiber optic portion of the cable for the camera system had failed. A contingency method that had been developed prior to the expedition to transmit the camera’s black and white video feed using one of the copper conductors in the fiber optic cable was implemented. After 7.75 h spent modifying the video system, the camera was deployed at 1215 h. The ship started maneuvering for reentry at 1350 h, Hole U1439C was reentered at 1405 h, and the camera was brought to the surface. Fill was encountered upon lowering the drill string to the previous coring depth and the hole had to be cleaned from 319.0 to 348.3 mbsf, resulting in Core U1439C-21G (0.1 m recovered). Coring resumed at 2015 h. Core U1439C-22R penetrated from 348.3 to 358.1 mbsf and recovered 1.4 m (14%).
Cores U1439C-19R to 20R contain the same purple-gray boninite pillow lava encountered in Cores 14R–18R.
A meeting was held to discuss the portable XRF instrument methodology and to compare analyses done with both the ICP-AES and portable XRF instruments.
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