Diamond Core Research Articles

Carbon nano-flake ball with a sandwich-structure composite of diamond core covered by graphite using single-step microwave plasma chemical vapor deposition

A three-dimensional nanostructure of carbon material similar to a desert rose stone, named the carbon nano-flake ball, was fabricated by a single-step microwave plasma chemical vapor deposition process. Silicon substrate pretreated with different methods was used to grow carbon nano-flake balls and to control their coverage ratio. The dimension of single carbon nano-flake ball was found to be within 10 μm and it was constructed from multiple nano-scale-thickness flakes at angles. In turn, the nano-scale-thickness flakes were composed of a sandwich-structured composite, which contained a diamond core covered by graphite. The width and length of separate flakes can exceed 1 μm. The measurement of field emission properties revealed that the turn-on electric field can be as low as 2.13 V/μm, which is better than a conventional diamond film. In addition, the growth mechanism of carbon nano-flake balls was proposed. The carbon species (CH, C2) formed a diamond cluster at the defects on the surface of silicon substrate or spots where Fe-based catalyst located. It was discovered that the deposition temperature and CN specie are the key factors to grow carbon nano-flake ball.

All-Diamond Microfiber Electrodes for Neurochemical Analysis

Neurochemical sensing with implantable microelectrodes has created multiple research opportunities in the field of neuroscience. The ability to record extracellular biopotentials and detect neurotransmitters with high sensitivity has enabled deeper understanding of brain and nervous system function. Diamond has many advantages over other electrode materials such as good biocompatibility, wide potential window, low double-layer capacitance, long-term stability, resistance to corrosion/fouling, and fabrication flexibility. In this work, we present a micromachined, implantable, all-diamond microfiber capable of reliable, precise neurochemical sensing. The all-diamond fiber consists of a conductive boron-doped polycrystalline diamond (BDD) core encapsulated in layers of insulating polycrystalline diamond (PCD) cladding. The PCD serves as a biocompatible and hermetic package while also acting as a dielectric barrier to prevent signal cross-talking. The all-diamond microelectrodes were thoroughly characterized using topographical and electrochemical methods. The capability for neurotransmitter sensing was completed using dopamine (DA) as the model analyte. Fast-scan cyclic voltammetry (FSCV) of DA was also completed to demonstrate the practicality for in vivo sensing at rapid rates. The fabrication is described in great detail and the capability for batch-scale process is demonstrated. These novel all-diamond microelectrodes have commercial-scale potential, generating a powerful tool for neurochemical analysis.

Investigations on the Wear Rate of Sintering Diamond Core Bit during the Hole Drilling Process of Al2O3 Bulletproof Ceramics

Bulletproof ceramics are usually hard and brittle with high elastic modulus, high compressive strength, and low tensile strength. While machining bulletproof ceramics, severe tool wear makes it difficult to obtain desired machining quality and efficiency, especially in hole drilling. In this work, an intensive experimental study on the overall wear rate of the sintering diamond thin‐wall core bit during the hole drilling of Al2O3 bulletproof ceramics (99 wt.%) has been carried out. The quality loss of the bit after each hole drilled was selected for representing the overall wear rate of the bit. Based on experimental data, the influences of the main bit performance and machining process parameters on the overall wear rate of the bit have been analyzed. According to the results discussed, under the test conditions, finer diamond grit, higher diamond concentration, lower number of water gaps, thinner wall thickness, or lower bit load all can decrease the wear rate of the bit. However, within a certain range, the spindle speed has little influence on the overall wear resistance of the bit, but when the spindle speed increases, the machining efficiency can be significantly improved. The results obtained in this work can offer a valuable reference for the use of sintering diamond thin‐wall core bits in the hole drilling of bulletproof ceramics.

A study on the failure mechanism and wear loss of impregnated diamond bits during machining process of armor ceramics

Thin-wall diamond core bits are usually recommended for the machining of relatively high-sized holes in engineering ceramics. However, during the machining process of engineering ceramics, the tools are usually considerably worn. In this work, the failure mechanism and wear loss of thin-wall impregnated diamond bits has been investigated experimentally during the machining process of Al2O3 armor engineering ceramics. In summary, the failure reasons of the bits can be divided into three cases: Bit skidding, twisted fracture of the bit clamp holder and breakup of the sintering body. The overall wear process of the bits can be roughly divided into three stages: The rapid wear, the stable wear and the sharp wear. The machining duration per hole presents an approximately periodic variation with the number of cumulatively machined holes. Under the experimental conditions, both the bit wear rate and the drilling rate present an approximately periodic variation with the cumulative drilling depth, whereas the corresponding periodic characteristics are not the same. During the hole-machining process, the wear loss of the sintering diamond bits is mainly concentrated on the matrix crown of the bits, but the wear of the matrix binder and the diamond grits on the outer cylindrical surface of the sintering body is negligible.

Self-organized multi-layered graphene-boron-doped diamond hybrid nanowalls for high-performance electron emission devices.

Carbon nanomaterials such as nanotubes, nanoflakes/nanowalls, and graphene have been used as electron sources due to their superior field electron emission (FEE) characteristics. However, these materials show poor stability and short lifetimes, which prevent their use in practical device applications. The aim of this study was to find an innovative nanomaterial possessing both high robustness and reliable FEE behavior. Herein, a hybrid structure of self-organized multi-layered graphene (MLG)-boron doped diamond (BDD) nanowall materials with superior FEE characteristics was successfully synthesized using a microwave plasma enhanced chemical vapor deposition process. Transmission electron microscopy reveals that the as-prepared carbon clusters have a uniform, dense, and sharp nanowall morphology with sp3 diamond cores encased by an sp2 MLG shell. Detailed nanoscale investigations conducted using peak force-controlled tunneling atomic force microscopy show that each of the core-shell structured carbon cluster fields emits electrons equally well. The MLG-BDD nanowall materials show a low turn-on field of 2.4 V μm-1, a high emission current density of 4.2 mA cm-2 at an applied field of 4.0 V μm-1, a large field enhancement factor of 4500, and prominently high lifetime stability (lasting for 700 min), which demonstrate the superiority of these materials over other hybrid nanostructured materials. The potential of these MLG-BDD hybrid nanowall materials in practical device applications was further illustrated by the plasma illumination behavior of a microplasma device with these materials as the cathode, where a low threshold voltage of 330 V (low threshold field of 330 V mm-1) and long plasma stability of 358 min were demonstrated. The fabrication of these hybrid nanowalls is straight forward and thereby opens up a pathway for the advancement of next-generation cathode materials for high brightness electron emission and microplasma-based display devices.

Feasibility study of delamination in rotary ultrasonic-assisted drilling of glass fiber reinforced plastics

Glass fiber reinforced plastics are used in variety of industrial and constructional applications for their superb mechanical and physical properties. Delamination is one of the most important and prevalent damages in machining of glass fiber reinforced plastics. Diamond core drills have the capability of simultaneously drilling and grinding of fiber reinforced plastics, which results in hole quality improvement. Rotary ultrasonic-assisted drilling is the new machining process to drill holes on fiber reinforced plastics and has attracted increasing attention in recent years. In this paper, thrust force and delamination in rotary ultrasonic-assisted drilling of glass fiber reinforced plastics using diamond core drill have been investigated. A proper ultrasonic system for a core drill in ABAQUS was designed and fabricated. Influence of ultrasonic vibration and then tool grain size, fiber-volume fraction and machining parameters including spindle speed and feed rate on thrust force and delamination was investigated. Higher thrust force induces more delamination. As a result of the study, less delamination was achieved in ultrasonic-assisted mode by using a tool with larger grain size onto lower fiber-volume fraction composites. Additionally, experiments showed that lower spindle speed and higher feed rate induce more delamination.

Parametric investigation of rotary ultrasonic drilling of carbon fiber reinforced plastics

Carbon fiber reinforced plastics are used in various industrial applications for their excellent properties. Rotary ultrasonic drilling is the new machining process used to drill holes on fiber-reinforced plastics and has been attracting increased attention in recent years. Dimensional tolerances are very important in machining of carbon fiber reinforced plastics. Additionally, diamond core drills are simultaneously drilling and grinding fiber reinforced plastics. This paper aims to investigate thrust force and dimensional tolerances including roundness and cylindricity in rotary ultrasonic drilling of carbon fiber reinforced plastics using diamond core drill. To this end, a proper ultrasonic system for a core drill in ABAQUS is designed and fabricated. Thrust force in rotary ultrasonic drilling when compared to conventional drilling reduced by up to 30%. Besides, roundness and cylindricity decreased by up to 80% and 72%, respectively. Afterwards, analysis of variance demonstrated that vibration is more influential than other machining parameters in order to improve the hole accuracy. That is, obtained exponential regression models predict roundness and cylindricity through machining parameters with high accuracy. Feed rate of 30 mm/min and spindle speed of 1400 r/min by exerting vibration on the tool is considered to be the optimized condition.

Wet Core Drilling of CFRP with an Electrodeposited Diamond Core Drill - Effects of Cutting Conditions on Chip Evacuation and Core Jamming

This study investigated the cutting characteristics of electrodeposited diamond core drill when used to drill a CFRP under wet condition. The effects of different tool shapes, grain sizes and feed rates were examined. A normal core drill, an eccentric with slits core drill (E.S.), and an eccentric with slits and chamfers core drill (E.S.C.) were used. The normal core drill had the shape of a hollow cylinder. The E.S. core drill had the inner cylinder shifted from the center of this tool and slits in the bottom of this tool. The E.S.C. core drill had chamfers on the periphery of this tool. The normal core drill caused severe workpiece core jamming even at 1st hole drilling, and its electro-deposited area was covered entirely by adhered chips. In the case of the E.S. core drill and E.S.C. core drill, the workpiece core did not jam and the thrust force was smaller than that of the normal core drill. The effect of chamfers was little. The E.S.C. core drill with #200 caused smaller surface roughness than that with #100. However, the thrust force was two times larger, and the delamination was observed at the exit point of the hole. In the lower feed rate per revolution the better surface roughness and the lower thrust force were obtained irrespective of the tool shape while the cutting speed showed little effect.

Carbon structure in nanodiamonds elucidated from Raman spectroscopy

Despite their name, nanodiamonds (ND) are comprised of a complex interplay of different carbon phases. The diamond core is surrounded by the shell consisting mostly of disordered sp3 carbon and graphene-like carbon (GLC). The complex structure makes the characterization of nanodiamonds (ND) a difficult challenge. Recent development of many varieties of NDs for different applications demands quick and reliable characterization of the content of various carbon fragments, as well as the estimation of the diamond core size. In this work, we apply Raman spectroscopy to study the structure of nanodiamonds from different origins, including those produced by detonation (DND), high pressure high temperature synthesis (HPHT), and pulsed laser irradiation (LND). The relative content of GLC, disordered and surface carbon can be easily determined from Raman spectra. In particular, we show how the content of different structure fragments is changed upon de-agglutination, surface oxidation and ion irradiation. We also compare the different ND production methods in terms of the structural uniformity of the nanoparticles. Raman spectroscopy provides unique quantitative tool for ND characterization; we believe that the present data will be useful for understanding the structure of diamond nanoparticles, and will provide the background for obtaining the NDs with desired properties.

Rock quality designation (RQD): time to rest in peace

Rock quality designation (RQD) was introduced by Don Deere in the mid-1960s as a means of using diamond core to classify rock for engineering purposes. Subsequently, it was incorporated into the rock mass rating (RMR) and Q-system classification methods that, worldwide, now play substantial roles in rock mechanics design, whether for tunnels, foundations, rock slopes or rock excavation. It is shown that a key facet of the definition of RQD is ignored in many parts of the world, and it is noted that there are several inherent limitations to the use of RQD. Based on mapping of rock formations by 17 independent professionals at different locations in Australia and South Africa, it is shown that differences in assessed RQD values result in significant errors in computed RMR and Q ratings, and also in geological strength index (GSI) and mining rock mass rating (MRMR). The introduction of a look-up chart for assessing GSI has effectively removed the need to measure, or estimate, RQD. It has been found that GSI values derived from the look-up chart are as valid as those derived by calculation from the original component parameters, and are satisfactorily consistent between professionals from diverse backgrounds. The look-up charts provide a quick and appropriate means of assessing GSI from exposures. GSI is, in turn, a useful rock mass strength index; one new application is presented for assessing potential erosion of unlined spillways in rock. Incorporation of RQD within the RMR and Q classification systems was a matter of historical development, and its incorporation into rock mass classifications is no longer necessary.

On the structure and impurities of a nominally homologous set of detonation nanodiamonds

Unexpected variations in the purity and structure of commercial detonation nanodiamonds (DNDs) is an ongoing issue. Unfortunately, influences of these variations and how they affect DND behaviors are seldom addressed. This work investigates nominally homologous commercial DNDs sold by a single vendor under the same item number but different lots. Paraffin wax and surfactant were discovered as the major organic contaminants in the DND samples along with metallic impurities. The relative quantities of these contaminants were correlated to discrepancies in the structure and crystallinity of DNDs. The DNDs containing more contaminants possessed thicker shells surrounding the diamond cores; the diamond crystallinity was observed to quickly disappear, on the order of several minutes, when exposed to 200kV electron beam. On the other hand, those DNDs carrying fewer impurities exhibited a stable diamond structure. The differences in metallic impurities were attributed to variations in the DND purification treatments, and did not appear to affect a morphological change under the electron beam. The present work demonstrates the negative effects of impurities in commercial DNDs on the content and stability of diamond carbons. The results also have implications on possible factors that must be considered when using commercial DNDs for advanced applications.

Simple Design of an Enzyme-Inspired Supported Catalyst Based on a Catalytic Triad

Summary Enzyme active sites afford an intricate interplay of functional groups to mediate complex organic and inorganic reactions. Many hydrolytic enzymes use a catalytic triad comprising three different functional residues—(Ser(-OH), Hist(-imidazole), Asp(-CO 2 H))—that catalyze the hydrolysis of numerous unique substrates. Inspired by this design, we have developed a simple one-step synthesis for preparing a new supported catalytic system in which the three reactive groups of the catalytic triad (alcohol, imidazole, and carboxylate) are incorporated into a single functional unit. These artificial active sites can be coupled to a solid-phase support (Merrifield resin) by copper(I)-catalyzed azide-alkyne cycloaddition "click chemistry," and their effectiveness as esterolysis catalysts was demonstrated. Furthermore, tuning the local hydrophobicity of the resin particles with an approach analogous to the native enzyme hydrophobic pocket increased the catalytic efficiency. Quantum mechanics and molecular dynamics computational modeling were used to probe the catalytic effect and suggested a concerted two-step mechanism and hydrophobic nanoenvironment similar to that of hydrolytic enzymes.

A comprehensive literature review reflecting fifteen years of debate regarding the representativity of reverse circulation vs blast hole drill sampling

Author Summary: Blast hole sampling is widely used for grade control by the mining industry all over the world, both in precious and base metal open pit mining. Blast hole (BH) samples are often regarded as inferior in comparison to “proper drill sampling” like reverse circulation (RC) and diamond (core) drilling (DD), and are accused of lacking representativity by the sampling community. The present paper aims at collecting all peer reviewed publications from 2000 onwards that concern open pit mine sampling performance of BH, RC and/or DD drill sampling. This will form a comprehensive literature review reflecting on the debate between the representativity of the different sampling methods. The literature review collected a total of 31 publications (two were more or less duplicates and one consisted of an abstract only). The main source for publications on RC and BH drill sampling were dedicated sampling conferences, other mining conferences and some publications were found in peer-reviewed journals. From the gathered publications, it is not possible to draw a general overall conclusion as to the superiority of one drill sampling method over another. Both RC and BH have advantages and disadvantages and the choice of system needs to be related to the ore type and to the mining conditions. The overall conclusion is that it is always necessary to evaluate the specific sampling system to be used in light of the Theory of Sampling (TOS) (and with respect to the characteristics of the ore to be mined). It is always necessary to ascertain that the specific drilling sampling system contemplated does not lead to hidden losses that could have been avoided or missed profits that could be gained with a more relevant and representative sampling system. It would appear that the mining industry is doomed to continue to follow local, often economy-driven objectives and sampling solutions even if these can be documented as inferior when seen in the light of the representativity imperative. A call is made for universal adherence to the principles laid down by TOS for representativity in the primary sampling stage, before economic, logistical or other (local) factors are allowed to intervene. What is the objective to analyse and to make decisions in the mining industry, based on samples that can be documented not to be representative?

Evidence for a Di-μ-oxo Diamond Core in the Mn(IV)/Fe(IV) Activation Intermediate of Ribonucleotide Reductase from Chlamydia trachomatis.

High-valent iron and manganese complexes effect some of the most challenging biochemical reactions known, including hydrocarbon and water oxidations associated with the global carbon cycle and oxygenic photosynthesis, respectively. Their extreme reactivity presents an impediment to structural characterization, but their biological importance and potential chemical utility have, nevertheless, motivated extensive efforts toward that end. Several such intermediates accumulate during activation of class I ribonucleotide reductase (RNR) β subunits, which self-assemble dimetal cofactors with stable one-electron oxidants that serve to initiate the enzyme's free-radical mechanism. In the class I-c β subunit from Chlamydia trachomatis, a heterodinuclear Mn(II)/Fe(II) complex reacts with dioxygen to form a Mn(IV)/Fe(IV) intermediate, which undergoes reduction of the iron site to produce the active Mn(IV)/Fe(III) cofactor. Herein, we assess the structure of the Mn(IV)/Fe(IV) activation intermediate using Fe- and Mn-edge extended X-ray absorption fine structure (EXAFS) analysis and multifrequency pulse electron paramagnetic resonance (EPR) spectroscopy. The EXAFS results reveal a metal-metal vector of 2.74-2.75 Å and an intense light-atom (C/N/O) scattering interaction 1.8 Å from the Fe. Pulse EPR data reveal an exchangeable deuterium hyperfine coupling of strength |T| = 0.7 MHz, but no stronger couplings. The results suggest that the intermediate possesses a di-μ-oxo diamond core structure with a terminal hydroxide ligand to the Mn(IV).

Application of Petrology & Geology to the Interpretation of Geophysical Data in Defining Economic Porphyry-Related Cu-Au Mineralisation Along the Ekuti Range, Morobe Province, PNG

Detailed petrologic and petrophysic data obtained from surface rock chip and diamond core of the Mt Leahy Tenement, Ekuti Range porphyry copper-gold exploration project area, Morobe Province, Papua New Guinea have been applied to interpretations of geologic setting and hydrothermal environment of mineralisation, and interpretations of airborne magnetic field data in defining a causative intrusion framework for mineralisation. Petrologic data confirm and refine a model of magmatic hydrothermal fluid sources for structurally confined mesothermal to epithermal style Cu, Au, Mo, Ag, Pb, Zn and Bi mineralisation within eroded composite granodiorite, quartz monzodiorite and diorite/andesite intrusion centres and hornfelsed metasedimentary rock, with potential for delineation of “disseminated” porphyry and hornfels styles of mineralisation. The application of petrophysic data, derived from petrology, to the interpretation of airborne magnetic field data defines three intrusion centres within the Leahy tenement: a northern and relatively deeply eroded Otibanda-Weke/Waikanda composite intrusion zone, and higher-level Kopekio and Ekoato intrusion domains, the latter with greater potential for discovery of low-grade high-tonnage style copper-gold mineralisation.

Robust Co-catalytic Performance of Nanodiamonds Loaded on WO3 for the Decomposition of Volatile Organic Compounds under Visible Light

Proper co-catalysts (usually noble metals), combined with semiconductor materials, are commonly needed to maximize the efficiency of photocatalysis. Search for cost-effective and practical alternatives for noble-metal co-catalysts is under intense investigation. In this work, nanodiamond (ND), which is a carbon nanomaterial with a unique sp3(core)/sp2(shell) structure, was combined with WO3 (as an alternative co-catalyst for Pt) and applied for the degradation of volatile organic compounds under visible light. NDs-loaded WO3 showed a highly enhanced photocatalytic activity for the degradation of acetaldehyde (∼17 times higher than bare WO3), which is more efficient than other well-known co-catalysts (Ag, Pd, Au, and CuO) loaded onto WO3 and comparable to Pt-loaded WO3. Various surface modifications of ND and photoelectochemical measurements revealed that the graphitic carbon shell (sp2) on the diamond core (sp3) plays a crucial role in charge separation and the subsequent interfacial charge transfer. As a...

Carbon isotopes of eclogite-hosted diamonds from the Nyurbinskaya kimberlite pipe, Yakutia: The metasomatic origin of diamonds

Carbon isotope compositions and the distribution of nitrogen and hydrogen in diamonds from 18 eclogites from Nurbinskaya kimberlites were studied in situ in polished plates. Cathodoluminescence images show that most of the diamonds have complex growth structures with distinctive core, intermediate and rim zones. In some diamonds the cores display dissolution features, and intermediate growth zones are separated from the cores by narrow rounded oscillatory zones. At least three crystals show interrupted multistage diamond growth; variations in δ13C of 2–3‰ occur across the contacts between distinct zones. Generally, δ13C within the diamond cores varies only by 1–2‰, in rare cases up to 3.3‰. δ13C values are usually lower in the intermediate zones and drop further towards the rims by up to 3‰. High-resolution SIMS profiles show that variations in δ13C across the diamond growth zones are sharp with no evidence of diffusive relaxation.Diamonds with predominantly tangential octahedral growth have a wide range in δ13C from −15.2‰ up to 9.0‰ (±0.4‰), and their nitrogen (N) contents vary between 30 and 1500at.ppm. Six diamonds show little internal variation along the isotopic profiles with changes in δ13C of only 0.3–0.9‰ around mean values ranging from −6‰ to −3‰. Five crystals are isotopically heavy, with relatively homogeneous δ13C up to 9‰. FTIR data show markedly different N concentrations and nitrogen aggregation states between major growth zones. This implies that the diamonds in eclogitic xenoliths from Nyurbinskaya pipe grew in multiple and interrupted growth events, probably from fluids enriched in K and H.The wide variations of δ13C in the studied eclogitic diamonds and identification of their anomalously positive δ13C values, combined with the wide range of high δ18O in garnets from the diamondiferous xenoliths of the Nyurbinskaya pipe, which are mostly outside of the mantle range, suggest a crustal contribution to the parental mantle-related fluids forming diamonds in these xenoliths and indicate the complex metasomatic evolution of the lithospheric mantle beneath the Nakynsky kimberlite field.

Heat Transfer of Drilling Tool Under Variable Cooling

The subject of research is the heat transfer process on the working face of the drilling borehole using diamond core bits. This problem is very important for development of new high-technology drilling where variable supply of mud is used. The aim of this article is defining the variable heat transfer coefficients on the drill tool surface. Methods of research are mathematical modeling and computational experiment. Historical review of publications and modern works related at this problem are conducted, and actuality of presented work is justified. The fluid dynamics of drill mud on the working face of borehole is needed for solving thermal problem. Thus, results of 3D modelling of fluid dynamics are presented as well. The outcome of modelling shows that heat transfer coefficient is changed into one direction only. The expressions for defining heat transfer coefficients as function from time were proposed, taking to account a mode of cooling. Based on the calculation of the average mud velocity field, heat transfer coefficients for core bit were defined. Obtained results of interest to determine the temperature regime of drilling tools and determination and energy saving mode with pulse drilling flushing.

Experimental Investigation and Optimization in Rotary Ultrasonic Drilling of C/C Composites

C/C composites are widely used in aviation and aerospace due to their low density, superior specific strength, special elastic modulus at elevated temperatures, small thermal expansion coefficient and high fracture toughness. However, there are numerous problems such as delamination, chipping, poor machining quality and tool wear in drilling of C/C composites due to inhomogeneous, anisotropic, wear resistance and varying thermal properties of the composites. In this paper, related experiments on rotary ultrasonic drilling of C/C composites using diamond core drill were conducted to compare the drilling force and machining quality of ultrasonic drilling with conventional drilling, analyze the rotary ultrasonic drilling mechanism and research the influence of spindle speed, feed rate and ultrasonic amplitude on the drilling force. Experimental results showed that rotary ultrasonic drilling can significantly improve the removal of the chips thus preventing the core drill blockage, effectively reduce the drilling force and improve processing quality. In addition, the drilling force decreased with increasing of spindle speed and ultrasonic amplitude, while it increased with increasing of feed rate. Finally, the cutting parameters were optimized by consideration of the drilling force and efficiency.

Hyperspectral interpretation of selected drill cores from orogenic gold deposits in central Victoria, Australia

ABSTRACTHyLogger hyperspectral data obtained from seven orogenic gold deposits in central Victoria, including Bendigo, Ballarat, Maldon, Fosterville, Costerfield, Castlemaine and Wildwood, are presented. The data demonstrate that fresh diamond drill core displays substantial mineralogical variation that can be attributed to the effects of cryptic hydrothermal alteration that might not otherwise be recognised. The most significant hyperspectral response lies in the white mica compositions, which vary in a systematic manner between high-Al muscovitic zones (Al–OH absorption around 2208 nm) that define a phyllic alteration halo around mineralised structures, and low-Al phengitic–chlorite zones (Al–OH absorption >2014 nm) inferred to represent either more distal alteration or possibly regional metamorphic background. An extensive ferroan dolomite alteration halo overlaps the phyllic and sulfidic alteration zones and extends beyond the sampled core in most instances. This ferroan dolomite halo has previously been defined petrographically, geochemically and using carbonate staining techniques, and is further characterised using thermal infrared hyperspectral data in drill core from the Ballarat goldfield. The mineralogical trends identified by the hyperspectral data are best developed in diamond drill core from the Costerfield, Fosterville and Ballarat goldfields, and are less pronounced at the other deposits. At Bendigo and Castlemaine the reasons for this are not immediately clear, but may be related to the close timing of gold mineralisation relative to peak metamorphism. The Maldon area lies within the contact aureole of the Harcourt Batholith and so has been thermally overprinted leading to the recrystallisation of earlier hydrothermal assemblages. The Wildwood deposit is similar to the Magdala deposit at Stawell and differs from the other goldfields in its geological setting, host rock lithologies and style of hydrothermal alteration, with the development of Fe-rich chlorite closely associated with gold mineralisation. The results demonstrate how hyperspectral data can be used to define large hydrothermal alteration footprints associated with orogenic gold mineralisation in central Victoria that are of direct benefit to mineral explorers, as well as independently characterising lithological variations in drill core.