Diamond Drill Research Articles

Physical Volcanology and Genesis of Komatiite-Associated Ni-Cu-(PGE) Mineralization in the C Zone, Bannockburn Township, Ontario

The C zone, located in Bannockburn Township approximately 30 km W of Matachewan, Ontario, is one of several komatiite-associated Ni-Cu-(PGE) deposits within the 2710 to 2704 Ma Tisdale volcanic episode of the Abitibi greenstone belt. The sulfides, host rocks, and country rocks are superbly exposed over a strike length of 150 m in glacially polished and hydraulically stripped outcrops and have been intersected in 53 diamond drill holes. The mineralized zone is up to 2.5 m thick and comprises (from base to top) massive to semimassive, net-textured, and disseminated sulfide facies characterized by a pyrrhotite-pentlandite-chalcopyrite-magnetite assemblage. The massive sulfide zone contains an anastomosing network of dextral and sinistral shears that are oriented broadly subparallel to the contacts with the footwall dacite and hanging-wall andesite. Some contacts with underlying dacites are sheared, but others are scalloped and bordered by skeletal-euhedral Fe-rich chromites and appear to be primary magmatic features. The footwall rocks grade from chloritized dacites within 20 to 30 cm of the contact into massive and brecciated plagioclase-phyric dacites farther away from the contact. The host unit is up to 8 m thick and comprises massive olivine porphyritic and ortho- to mesocumulate komatiite in the eastern and central parts and a texturally heterolithic komatiite breccia in the western part. The breccia is composed of subrounded to subangular clasts 1 to 30 cm in length that exhibit mainly fine ( 80 m). The komatiitic sequence at the C zone is much thinner than most other sequences within the Tisdale volcanic episode and is oriented oblique to the NW trend of the regional stratigraphy, but all contacts appear conformable and all younging indicators are uniformly to the SSE, suggesting that the local sequence is intact. The C zone is similar in many respects to other type I (Kambalda-type) komatiite-associated Ni-Cu-(PGE) deposits in the Abitibi greenstone belt but differs by not being confined within a well-developed footwall embayment and in being partly hosted by komatiitic breccias. The C zone Ni-Cu-(PGE) mineralization appears to be hosted in the eastern part of the stripped exposure by a thin lava pathway and in the western part by breccias formed via lateral breakout and roof collapse.

A new strategy of carbon fiber reinforced plastic drilling evaluation using thermal measurement

Carbon fiber reinforced plastic composites are being increasingly used for more applications. The evaluation of hole-drilling in these composites remains a difficult and unsolved problem. The drilling process for multi-material composites is quite different than those for their more conventional metal counterparts. In the research reported here, the drilling ability and durability of drills used for drilling carbon fiber reinforced plastic composites, made with a diamond layer was deposited by chemical vapor deposition are evaluated with different r/min. Spindle speed was fixed reasoning based in abundant previous works. A thermal camera and related techniques were used to evaluate chip removal, temperature measurement inside the hole, associated thermal damage during the drilling operation, in an effort to ascertain optimal drilling conditions. Currently, chemical vapor deposition diamond drills appear to produce better holes at lower r/min.

Sequence stratigraphy, provenance, C and O isotopic composition, and correlation of the late Paleoproterozoic–early Mesoproterozoic upper Hornby Bay and lower Dismal Lakes groups, NWT and Nunavut

Late Paleoproterozoic basins of Canada's north, including the Thelon, Athabasca, and Hornby Bay basins, can be broadly correlated based on similarities in age, sequence stratigraphy, paleocurrents, and detrital zircon provenance, but their detailed evolution is poorly understood and their age and lateral equivalencies are poorly constrained. This study contributes to the understanding of sedimentary basins during a critical interval of time, representing the latest stages of amalgamation of the supercontinent Laurentia/Nuna, through a detailed study of the Hornby Bay Basin. The Hornby Bay Basin strata have been divided into four unconformity-bounded subsequences, A1, A2, A3, A4, that belong to the first of three unconformity-bounded post-Hudsonian Proterozoic stratigraphic packages in northwestern Canada. Subsequences A2 (>1600Ma) and A3 (<1600–1270Ma) of the Hornby Bay Basin were intersected during diamond drilling for uranium exploration. Sequence stratigraphic interpretations reveal that the subsequence A2–A3 boundary lies below the LeRoux Formation, which forms the base of the Dismal Lakes Group, a critical relationship that was previously disputed. Stratigraphic patterns in the late stages of development of the Hornby Bay Basin are considered to have been largely controlled by the Paleoproterozoic Forward Orogeny (∼1600Ma), rather than by global eustasy.Analysis of Sm–Nd isotopes on mudrocks yielded isotopic compositions in the range −8.2 to −2.3 (ɛNd(1600Ma)) in subsequence A2 and −9.8 to −5.0 (ɛNd(1400Ma)) in subsequence A3. An ɛNd versus time graph illustrates two distinct groupings that plot within known isotopic evolution fields of the Taltson-Thelon Tectonic Zone, and the Great Bear Magmatic Zone. Sediment provenance was strongly influenced by the Paleoproterozoic Forward Orogeny, but there are no significant changes in sedimentary provenance across the A2–A3 sequence boundary. Stable isotope analyses of C and O in the dolomitic East River Formation of subsequence A2 reveal a relatively monotonous signal with an average of −0.5‰ δ13C and −8.76‰ δ18O, which is consistent with global values of other late Paleoproterozoic carbonate successions. Enriched Mn values and depleted Sr values, however, suggest that the East River carbonate rocks experienced some degree of meteoric alteration; it is unknown how much this alteration affected stable isotope compositions.Based on similarities in sedimentary provenance, age, and sequence stratigraphy, subsequence A2 of the Hornby Bay Group is correlated with the Wernecke Supergroup (Yukon). The latter is interpreted to represent the deep-water distal equivalent of the upper Hornby Bay Group in a westward-deepening basin. Deposition of subsequence A2 is recorded across North America and is mirrored by deep-water sedimentation along the eastern margin of the North Australian craton. The tectonic evolution of subsequence A2 in Laurentia is therefore remarkably similar to that of the North Australian craton up to ∼1600Ma, the age of the Forward Orogeny, and this has implications for interpretation of the latest stages of accretion of the supercontinent Nuna.

Drilling of SiCp/Al Composites with Electroplating Diamond Drills

SiCp/Al composites have been used in a number of engineering applications including the consumer goods. However, the machining of these materials is very difficult because of the abrasive characteristics of the reinforced particulates. In this paper drilling studies on SiCp/Al composites with high volume fraction and large size SiC particles have been conducted by using electroplating diamond drills, and the influences of the cutting speed on the drilling force and surface roughness were investigated.

Critical Investigation of Wear Behaviour of WC Drill Bit Buttons

Mining and petroleum drill bits are subjected to highly abrasive rock and high-velocity fluids that cause severe wear and erosion in service. To augment the rate of penetration and minimize the cost per foot, such drill bits are subjected to increasing rotary speeds and weight. A rotary/percussive drill typically hits the rock 50 times per second with hydraulic impact pressure of about 170–200 bar and feed pressure of about 90–100 bar, while rotating at 75–200 rpm. The drill rig delivers a high-velocity flow of drilling fluid onto the rock surface to dislodge cuttings and cool the bit. The impingement of high-velocity drilling fluid with entrained cuttings accelerates the erosion rate of the bit. Also, high service temperature contributes to softening of the rock for increased penetration. Hence, there is a need to optimize the drilling process and balance the wear rate and penetration rate simultaneously. This paper presents an experimental scanning electron microscopy (SEM) study of electroplated (nickel-bonded) diamond drills for different wear modes.

Modeling and analysis of performances in drilling hybrid metal matrix composites using D-optimal design

The present paper deals with the modeling and analysis of machining responses such as the thrust force, surface roughness, burr height, and tool wear in the drilling of hybrid metal matrix composites using carbide, coated carbide, and polycrystalline diamond drills. Experiments are conducted on Al 356 aluminum alloy reinforced with silicon carbide of size 25 μm and mica of size 45 μm. Machining parameters such as spindle speed, feed rate, and weight percent of silicon carbide are chosen as the numerical factors; the drill material is considered as the categorical factor. An experimental plan of a four-factor (three numerical plus one categorical) D-optimal design based on the response surface methodology is employed to carry out the experimental study. The results indicated that the predicted values through the developed model are well in agreement with the experimental results. The results also indicated that the method used is effectively applied for the modeling and analysis of drilling parameters in drilling hybrid metal matrix composites.

The constrained magnetic modelling of the Wallaby gold deposit, Western Australia

The Wallaby Gold deposit is located 25km southwest of Laverton within the Eastern Goldfields Province of Western Australia. Gold mineralisation is hosted within a mafic conglomerate, intruded by a south-plunging magnetite-actinolite-epidote-calcite altered syenite pipe. Regions of low susceptibility within the pipe are associated with gold mineralisation. Airborne magnetic data from the Wallaby Gold deposit was inverted using the University of British Colombia Geophysical Inversion Facility MAGINV3D code to produce a 3D model of the subsurface magnetic susceptibility. Magnetic susceptibility measurements acquired at 1m intervals on diamond drill core were used to constrain the results of the inversion. This was facilitated using the Sparse Constraint Model Builder, which creates a physical property model based on existing geological, geophysical or geochemical measurements to then be applied within the UBC-GIF inversion code. The constrained inversion defined regions of low magnetic susceptibility within the outer high magnetic susceptible zones of the alteration pipe and potential mine-scale structural features can be interpreted. This is useful information given the structural control on gold mineralisation at Wallaby and its association with regions of reduced magnetic susceptibility.

Utilização de critérios geoestatísticos para comparação de malha de sondagem visando à maximização da quantidade de recursos

A proposta básica desse estudo é definir malhas ótimas de sondagem a serem aplicadas em pesquisas futuras de jazidas de minério de ferro. Realizou-se um estudo geoestatístico utilizando-se como parâmetro de otimização, a distribuição das classes dos recursos, obtidas a partir do Índice de Risco (IR), adotado como padrão, na avaliação de depósitos e minas de ferro pela Vale. Esse índice baseia-se no emprego da krigagem da indicatriz de minério para classificação dos recursos, avaliando-se, então, a influência da variação da malha de sondagem na categorização dos mesmos, pela criação de malhas regulares de sondagem "virtuais" com espaçamentos diversos. Estudos comparativos foram realizados em minas existentes e em projetos, tanto no Quadrilátero Ferrífero, quanto em Carajás, obtendo-se malhas de sondagem indicativas por província, sendo que, para novas áreas, criou-se uma metodologia de pesquisa sequencial, com adensamento gradativo da malha de sondagem e avaliação dos riscos em cada etapa.

Quantitative Mineralogy from Infrared Spectroscopic Data. I. Validation of Mineral Abundance and Composition Scripts at the Rocklea Channel Iron Deposit in Western Australia

Visible-near to shortwave infrared reflectance spectra (VNIR-SWIR—400–2,500 nm wavelength region) provide quantitative measurements of mineral abundances and mineral physicochemistries from drill core samples of channel iron ore. The infrared spectral reflectance measurements of drill core samples from the Rocklea channel iron deposit, located in the Hamersley Basin of Western Australia, were validated against X-ray flouresence (XRF) and X-ray diffraction (XRD). The reflectance data were collected using a CSIRO Hy-Logging™ system from 180 reverse circulation and 14 diamond drill cores spanning a depth from surface to 55 m below surface, intersecting the Rocklea deposit. The mineralogy of this channel iron deposit comprises chiefly goethite (both vitreous and ochreous forms) with lesser amounts of hematite and variable amounts of quartz, kaolinite, smectite (both dioctahedral and trioctahedral varieties), and carbonate (both dolomite and calcite). Iron ore and waste rock mineralogy were extracted from the infrared spectroscopic reflectance data using the geometry (depth/wavelength) of continuum-removed reflectance spectra, with depths of absorption features proportional to mineral abundance and wavelength positions proportional to chemical composition. For any one mineral, a number of its diagnostic spectral features are used to determine its mineral abundance and composition, in order to avoid complications with minerals that spectrally overlap with part of the diagnostic spectral features of the mineral of interest. This method that combines multiple spectral features to identify and quantify minerals is transferable to all types of infrared reflectance spectroscopic data collected from drill core to satellites. Final products include: iron (oxyhydr-)oxide content (root mean square error (RMSE) 9.1 wt % Fe); Al clay content (RMSE 3.9 wt % Al 2 O 3 ); hematite/goethite ratio (RMSE 9.0 wt % goethite); vitreous versus ochreous goethite (not easily measured using other analytical techniques); clay mineral type (kaolinite, montmorillonite and nontronite); and carbonate composition (dolomite vs. calcite). The Rocklea infrared reflectance spectroscopy-based mineral abundance and composition results have been used in an associated study to characterize the architecture of the Rocklea channel iron deposit, with implications for exploration, mining, and ore genesis.

Scientific drilling of speleothems - a technical note

This short article provides detailed descriptions of custom-made and commercially available hand-held drilling gear and options for water-flushing units specifically designed to obtained good-quality core material from speleothems even in remote cave regions. We use small-diameter (6-7 mm) diamond drill bits to obtain aliquots of calcite (as little as a few hundreds of milligram) from the interior of the basal part of in-situ stalagmites. These small cores are used to date the onset of stalagmite growth and occasionally to obtain other compositional information. Larger diameter drill bits produce cores 25-32 mm in diameter and up to 1.3 m in length which reveal internal structures and provide axial transects for chemical and isotope analysis and material for preparation of thin sections. This system has been successfully employed to sample flowstone and thick stalagmites. Given the growing interest in speleothem as archives of past environmental change, careful sample selection is primordial to keep the impact of sampling in these unique environments at a minimum. Low-invasive drilling is an essential technique and maximizes the amount of information gained.

Research on the Design of Diamond Size in Diamond Drill Bits and Diamond Saw Blades

In this paper, it is assumed that diamond’s cross-section is hexagonal, which is similar to the actual condition. At first the diamond cutting depth of diamond drill bits and diamond saw blades has been calculated and analyzed. A variety of diamond size and diamond exposure difference has also been calculated and analyzed. It is shown that the cutting depth of single diamond was generally below 0.02mm and the difference on diamond exposure between coarse and fine diamond must be less than diamond cutting depth to achieve efficient rock breaking. Some diamond size design methods are acquired via the calculations and analysis.

The Santa Rita Nickel Sulfide Deposit in the Fazenda Mirabela Intrusion, Bahia, Brazil: Geology, Sulfide Geochemistry, and Genesis

The Santa Rita ore zone within the Fazenda Mirabela intrusion is an unusual example of high-tonnage magmatic Ni-Cu-PGE sulfide mineralization developed as a stratiform layer within the main cumulus sequence of a layered intrusion. The intrusion as a whole is about 4 × 2.5 km in outcrop dimensions and at least 3 km in original maximum stratigraphic thickness with an original boat-shaped morphology. The ore zone comprises a 50- to 200-m-thick interval containing up to 5 wt percent disseminated sulfides within a sequence of mostly unaltered harzburgites and orthopyroxenites. This orthopyroxene-dominated sequence lies between the dominantly olivine rich cumulates that comprise the lower half of the intrusion and the gabbroic cumulates that make up the upper half. Sulfide tenor variations and silicate host-rock compositions have been derived from a very large database of continuous assays of more than 500 diamond drill cores. Consistent patterns of sulfide tenor—gradually decreasing Ni from over 20 to about 10 wt percent, near-constant Cu and gradually decreasing PGEs with cyclically varying Pt/Pd ratios—are found within the Santa Rita ore zone across the entire intrusion and display relatively little lateral variability. The position of the sulfide mineralization envelope within the harzburgite-orthopyroxenite package migrates to higher stratigraphic levels from the northern to the southern margin of the intrusion. Maximum grades and thicknesses correlate with the maximum thickness of orthopyroxene-bearing cumulates, asymmetrically disposed toward the southern margin of the intrusion. Nickel tenors of the sulfides range from 15 to 25 wt percent, exceptionally high for rocks with relatively low values of MgO/(MgO + FeO) and are closer to the typical values observed in komatiite-hosted deposits, although Cu tenors (typically 5–8 wt %) are much higher than komatiite values. Sulfide PGE tenors range from less than 100 ppb to greater than 10 ppm of both Pt and Pd, with maximum values in S-poor rocks at the base of the sulfide-bearing interval. PGEs become significantly more depleted toward the top of the Santa Rita zone. We attribute these features, along with the localization of the sulfide-bearing interval at the contact between ultramafic and mafic cumulates, to mixing of an initially S-undersaturated, moderately Ni enriched resident magma with a relatively low Ni, PGE-depleted, significantly lower temperature replenishing magma charged with suspended sulfide liquid droplets.

Quantification of Ni laterite mineralogy and composition: a new approach

Quantification of the chemical and mineralogical composition of Ni-bearing laterites is challenged by their complex nature, with the distribution of Ni and other metals controlled by a number of phases. Anew approach to predict the Ni (and Fe, Mg) composition of Ni laterites more reliably was tested using samples from drill holes from the Siberia North and Highway deposits. These deposits, selected as examples of (siliceous) oxide-style lateritic deposits, form part of the Kalgoorlie Nickel Project (KNP) in the north-eastern Yilgarn, Western Australia. Diffuse reflectance spectra over the 380–2500 nm wavelength range, measured using the CSIRO HyChips™ automated scanning system, were integrated with a multi-element dataset for 1 m-composite pulp samples using partial least-squares regression (PLSR) analysis. PLSR cross-validation models were developed to predict Ni, MgO and FeO, contents in samples with bulk composition limits of >0.08 wt% Ni and <6 wt% MgO. Calibration and validation models showed a strong, linear trend for characterising FeO and, to a lesser extent, Ni content, whereas reflectance spectroscopic-chemical models for predicting MgO content were less reliable. This reflected the prevailing mineralogy and associated element distribution within the oxide laterite profiles. For example, Fe and Ni distribution is controlled by relatively few minerals—predominantly goethite and, to a lesser extent, the Fe3+-bearing smectite, nontronite. Magnesium is associated with a range of Mg-bearing minerals, some of which are compositionally complex and include serpentine, talc, chlorite, smectite and carbonates (e.g. dolomite and magnesite). The MgO abundance alone does not reflect the varied mineralogy of samples with relatively high MgO contents, which can be spectrally distinct. Hence, samples with similar Mg contents, although comprising Mg-bearing minerals with distinct reflectance spectra, were difficult to model (e.g. smectite vs Mg carbonates). The findings of this study demonstrate that characterisation of Ni laterite chemistry may be achieved as part of routine logging of either drill cuttings or diamond drill core using PLSR analysis, but a detailed understanding of the mineral–element association is essential for reliable predictive analysis.

Epidote–clinozoisite as a hyperspectral tool in exploration for Archean gold

Hyperspectral analysis at seven gold deposits within the eastern Yilgarn Craton of Western Australia has revealed significant occurrences of previously unrecognised clinozoisite, and spatial relationships between the distribution of clinozoisite, epidote and gold deposits. Here we report the development of an index to allow the systematic spectral mapping of the epidote–clinozoisite solid solution. The combination of the wavelength position and depth of the 1550 nm absorption was used to characterise the solid- solution series spectrally. The spectral responses from CSIRO HyChips™, fitted with an Analytical Spectral Devices (ASD) FieldSpec-3 spectrometer, and a SisuCHEMA™ spectral-imaging camera were calibrated against electron microbe analyses of epidote–clinozoisite. The spectral-imaging camera helped resolve correlations for samples with complex paragenetic histories. Textural studies found genetic links between epidote and Mg-chlorite, and between clinozoisite and Fe-chlorite, with each mineral combination part of separate, diagnostic hydrothermal assemblages. Spectra from epidote–clinozoisite-dominated veins showed that shifts in the 2250 nm absorption correlate with epidote–clinozoisite composition and not with chlorite composition, and that coexisting amphibole phases have a closer compositional tie than chlorite in the given samples. The genetic affiliation, yet compositional discordance, between coexisting epidote–clinozoisite and chlorite suggests that the compositional spectral index associated with each are wholly independent, but in combination are diagnostic for the mapping of separate hydrothermal assemblages. Of the newly defined compositional relationships, vein-hosted clinozoisite was found to be a proxy for pre-existing structurally-controlled hydrothermal tschermakite. A comparison of spectral and stable isotopic characteristics from diamond drill hole CD5026, St Ives mining camp, shows correlations between the epidote–clinozoisite spectral index and δ13C of carbonate and δ34S of sulfide. Such correlations imply a redox control on the distribution of clinozoisite and epidote, and mean that the spectral logging of epidote–clinozoisite transitions can serve as a proxy for mapping paleoredox gradients.

CVD 다이아몬드 및 PCD이 드릴을 이용한 항공용 CFRP 복합재료의 홀 가공성 비교

최근 항공용 재료 산업 분야에서 널리 사용되고 있는 CFRP의 활용이 증가되고 있다. 하지만, CFRP와 같은 복합재료 부품의 결합 시에 단점이 있다. 복합재료를 이용한 다양한 구조를 제조하기 위해선 많은 홀 가공이 필요하다. 일반적으로 CFRP 홀 가공시 내구성이 매우 강한 polycrystalline crystalline diamond (PCD) 드릴을 사용한다. 하지만, 단가가 비싸고 가공 속도가 느리기 때문에 내구성은 PCD 드릴에 비해 약하나 드릴 형상 변화를 통해 가공 속도를 조절 할 수 있고, 비교적 가격이 저렴한 chemical vapor deposition (CVD) 다이아몬드 코팅 드릴의 사용량이 증가 되고 있다. 본 연구에서는. PCD 드릴과 CVD 다이아몬드 코팅 드릴의 홀 가공성을 비교 평가하였다. 먼저, 홀 가공 조건 식 (날당 이송량, 절삭 속도)을 이용하여 CFRP 홀 가공성을 평가했으며, CFRP 가공 시 드릴링 과정에서 발생하는 시편 내부의 열적 손상 정도를 비교했다. 열화상 카메라 촬영한 홀 가공 시 발생되는 온도를 이용한 경험식을 만들어 두 드릴의 발열 정도에 따른 홀 가공성을 비교 평가하였다. 또한, 홀 가공 시 발생하는 칩(chip) 배출 여부에 따른 홀 내부의 상태를 평가하여 CVD 다이아몬드 코팅 드릴과 PCD 드릴의 CFRP 홀 가공성을 비교했다. 전반적으로 PCD 드릴의 홀 가공성이 CVD 다이아몬드 드릴에 비해 우수한 성능을 나타냈지만, 홀 생성 속도는 CVD 다이아몬드 드릴이 PCD 드릴에 비해 빠른 결과를 나타냈다. Recently CFRP laminate joints process by bolts and nets are developed rapidly in aircraft industries. However, there are serious drawback during jointing process. Many hole processes are needed for the manufacturing and structural applications using composite materials. Generally, very durable polycrystalline crystalline diamond (PCD) drill has been used for the CFRP hole process. However, due to the expensive price and slow process speed, chemical vapor deposition (CVD) diamond drill has been used increasingly which are relatively-low durability but easily-adjustable process speed via drill shape change and price is much lower. In this study, the comparison of hole process between PCD and CVD diamond coated drills was done. First of all, CFRP hole processbility was evaluated using the equations of hole processing conditions (feed amount per blade, feed speed). The comparison on thermal damage occurring from the CFRP specimen was also studied during drilling process. Empirical equation was made from the temperature photo profile being taken during hole process by infrared thermal camera. In addition, hole processability was compared by checking hole inside condition upon chip exhausting state for two drills. Generally, although the PCD can exhibit better hole processability, hole processing speed of CVD diamond drill exhibited faster than PCD case.

Sequence and carbon isotopic stratigraphy of the Neoproterozoic Roan Group strata of the Zambian copperbelt

The Neoproterozoic Roan Group in northern Zambia is host to numerous world class stratiform sediment-hosted Cu ores that occur around the transition from basal continental clastics to an overlying shallow marine succession. The latter can be considered in terms of six sedimentary facies deposited within a mixed clastic and carbonate barred basin margin environment. Sequence stratigraphic analysis, based on palaeo-bathymetric cycles defined by vertical facies changes in sections constructed from detailed logging of diamond drill cores, allows the definition of seven sedimentary sequences. Accommodation for the lowermost two sequences, which host the bulk of the copper ores, was generated by half-graben development during active extension. The subsequent two sequences record denudation of tectonically generated relief and evolution to a laterally extensive, low-relief, basin margin carbonate platform during a period of tectonic quiescence. The uppermost sequences that coincide with the Mwashia Subgroup, record the resumption of tectonically generated accommodation that may reflect the onset of the breakup of Rodinia. Carbon isotopic profiles through the Roan succession in Zambia show two secular δ 13C excursions of more than 10‰ to values of <−5‰ that can be correlated to the global curve for the Cryogenian. The upper excursion occurs below the Sturtian Grand Conglomérat and is therefore interpreted to record the Islay anomaly. The lower excursion is interpreted to record the Bitter Springs stage, which occurs prior to the Sturtian glacials in a number of other Cryogenian sections where, as is the case in the Roan Group section in Zambia, it is not associated with glacial strata.

Research on Embedding Strength of Diamond

It is stated that Diamond saw blades requires high embedding strength of the diamond, while diamond drill bits do not. It is necessary to improve the embedding strength of diamond in diamond saw blades, rather than in the diamond drilling bits. It is recommended to count the number of diamond particles on the matrix surface and get the embedding strength of diamond by calculation. Another recommendation is to use the compound powder of cobalt and tungsten carbide for pelletizing in order to improve the embedding strength of diamond and lower the cost of matrix. There are people studying how to raise embedding strength of diamond, for both diamond saw blades and diamond drilling bit. However, the requirements for embedding strength of diamond saw blades and diamond drilling bit are different. The following parts include the analysis for this problem.

Nature and origin of the protolith succession to the Paleoproterozoic Serra do Navio manganese deposit, Amapa Province, Brazil

Until its closure in 1997, the Serra do Navio deposit, located in Amapá Province, Brazil, was one of the most important sources of high-grade manganese ore to the North American market. The high-grade manganese oxide ores were derived by lateritic weathering from metasedimentary manganese protoliths of the Serra do Navio Formation. The local geological context and nature of this protolith succession are not well understood, due to poor surface outcrop conditions, and intense deformation. However, based on similar age, regional tectonic setting and lithology the Paleoproterozoic volcanosedimentary succession that includes the Serra do Navio Formation is widely believed to be similar in origin and laterally equivalent to the Birimian Supergroup in West Africa. For the present investigation several diamond drill cores intersecting the protolith succession were studied. Detailed petrographic and whole rock geochemical studies permit distinction of two fundamental lithological groups comprising of a total of five lithotypes. Biotite schist and graphitic schist lithotypes are interpreted as former metapelites. A greywacke or pyroclastic protolith cannot be excluded for the biotite schist, whereas the graphitic schist certainly originated as a sulfide-rich carbonaceous mudstone. Rhodochrosite marble, Mn-calcite marble and Mn-silicate rock are grouped together as manganiferous carbonate rocks. Manganese lutite constitutes the most probable protolith for rhodochrosite marble, whereas Mn-calcite marble was derived from Mn-rich marl and Mn-silicate rock from variable mixtures of Mn-rich marl and chert.The sedimentary succession at the Serra do Navio deposit is similar to that encountered at many other black shale and chert-hosted Mn carbonate deposits. A metallogenetic model is proposed, predicting deposition of manganese and closely associated chert in intra-arc basins, in environments that were bypassed by distal siliciclastic (carbonaceous mud) and proximal pyroclastic/siliciclastic detritus. Positive Ce anomalies and δ13CVPDB values of −4.3 to −9.4 per mill suggest that manganiferous carbonates derived during suboxic diagenesis from sedimentary Mn4+ oxyhydroxide precipitates. Metamorphic alteration of manganese carbonate–chert assemblages resulted in the formation of Mn-silicates, most importantly rhodonite and tephroite; porphyroblastic spessartine formed where Mn-carbonate reacted with aluminous clay minerals. Microthermometric studies of fluid inclusions in spessartine porphyroblasts suggests that peak metamorphic conditions reached the upper greenschist facies (1–2kbars and 400–500°C). Retrograde metamorphism is marked by partial re-carbonation, expressed by the formation of small volumes of rhodochrosite, and Mn-calcite that are closely associated with quartz, chlorite and minor amounts of sulfides related to post-metamorphic veinlets. It is this metamorphosed succession that sourced the high-grade manganese oxide ores during prolonged lateritic weathering.

Endoscopic Extradural Anterior Clinoidectomy via Supraorbital Keyhole: A Cadaveric Study

Anterior clinoidectomy is an essential preliminary step for parasellar and pericavernous sinus surgery. Endoscopy is a widely accepted modality for neurosurgical strategies and is becoming more important in treating conditions involving the cranial base. To determine the feasibility of endoscopic extradural anterior clinoidectomy via the supraorbital keyhole. Eight fresh cadaver heads were studied using 4-mm, 0- and 30-degree rigid endoscopes to perform endoscopic extradural anterior clinoidectomy. We also evaluated a bony landmark for this technique in 36 dry craniums. An endoscope was introduced into the extradural space created via a supraorbital keyhole craniotomy. The periorbita and the duplication of the dura extending to the temporal lobe dura and periorbita were exposed by drilling. Anterior clinoidectomy proceeded using a diamond drill under endoscopic visualization without a dural incision. A submerged view with continuous irrigation through an endoscopic sheath maintained clear visibility while drilling. A small bony eminence at the transition between the sphenoid ridge and the anterior clinoid process, which is an anatomic landmark for endoscopic extradural anterior clinoidectomy, was identified in 57.4% of 36 adult dry craniums. The endoscopic extradural procedure can accomplish reliable anterior clinoidectomy under superb endoscopic visualization. This method would be applicable to parasellar and cavernous sinus surgery combined with keyhole or conventional craniotomy.

Study on Fabrication and Cutting Performance of CVD Diamond Coated Drills in Machining the Carbon Fiber Reinforced Plastics

Carbon fiber reinforced plastics (CFRP) have been widely used for manufacturing spacecraft, aircraft and automobile structural parts in aerospace and automotive industries. However, CFRP is a kind of hard machining materials and conventional tungsten carbide drills always experience severe tool wear, and thus short lifetime in the CFRP drilling process. In this paper, the CVD diamond films are deposited on the surface of cobalt cemented tungsten carbide (WC–Co) drills using hot filament chemical vapor deposition (HFCVD) method. Scanning electron microscope (SEM) is adopted to investigate the surface morphology of as-fabricated CVD diamond coated drills, additional analysis using Raman spectrum also indicates the high purity of sp3 phase of as-deposited diamond film. Furthermore, the machining performance of as-fabricated CVD diamond coated drills is examined in drilling the CFRP, comparing with the uncoated WC-Co drills. The chisel edge and primary cutting edge wear of drills are studied using the tool microscope. The results show that as-fabricated CVD diamond coated drills exhibit a much elongated lifetime than that of uncoated WC-Co drills, and also smoother surface finish of machined holes, which is supposed to be attributed to the excellent wear resistance and satisfied adhesive strength between the as-deposited diamond films and drills.