Assessing the Limitations of Effective Number of Samples for Finding the Uncertainty of the Mean of Correlated Data

The efficacy of recent and classical theories on the uncertainty of the mean of correlated data have been investigated. A variety of very large data sets make it possible to show that, under circumstances that are often too expensive to achieve, the integral time scale can be used to determine the effective number of independent samples, and therefore the uncertainty of the mean. To do so, the data set must be sufficiently large that it may be divided into many records, each of which is many integral time scales long. In this circumstance, all lags of the autocorrelation should be integrated to determine the integral scale. Some secondary findings include that the classical definition of the integral time scale goes identically to zero if a single record of any length is used and demonstration that measuring the integral scale requires ensemble averaging. Estimation of the integral time scale for a single record requires that the integration of the autocorrelation be truncated. This works well for signals where anti-correlation is not present. Additionally, for anti-correlated samples, the effective number of samples exceeds the number of acquired samples

Hidden Treasures: The Library Special Collections at Highland Theological College UHI

This paper details the library special collections material held at the library of Highland Theological College, University of the Highlands and Islands. Our three primary special collections are the focus of this article, The William Temple Collection, The Rutherford House Collection, and the Fort Augustus Collection. We detail here the story behind these collections entering our custody and proceed to highlight a selection of monographs of provenance and personal interest. This paper constitutes original research into the collections, building upon a foundation laid by the late college librarian, Mr. Martin Cameron, (1953-2019) who curated the collections over some twenty years. We also discuss the curation two new collections – The Liturgical Music Collection, comprising sheet music and musical sources from the Fort Augustus Collection, and the Historical Texts Collection, comprising the library’s oldest books of academic interest

Contrasting composition of metasomatic and metamorphic scapolite in the Eastern Fold Belt, Northwest Queensland, Australia

The Proterozoic Eastern Fold Belt (EFB) of the Mount Isa Inlier, Australia, preserves one of the largest areas of scapolite-rich rock in the world, and is comparable to several other districts of similar age and metallogenic affinity. The close temporal and spatial association between Cl-rich scapolite and Cu-Au miner-alization in the EFB implies that scapolite could be a useful indicator of mineralized systems. The occurrence of metamorphic scapolite and multiple generations of metasomatic scapolite apparently unrelated to Cu-Au mineralization complicate this relationship. However, we propose that scapolite of various generations can be differentiated on textural, chemical and mineralogical grounds, where metamorphic scapolite (marialite; Mas. so) typically contains less Cl and Na and more Ca, Al and C than those derived via metasomatism (Maso.95). Among the metasomatic scapolites, those associated with Cu-(Au) mineralization have higher Cl and Na (Ma>7o). Texturally, metasomatic scapolite fonns as irregular rounded growths, or as subhedral to euhedral vein-fill, as opposed to metamorphic scapolite that typically fanned cauliflower-shaped porphyroblasts. A primary rock control is also evident \Vhere metamorphic scapolite is restricted to calc-silicate rocks (c. 1.7 Ga) as opposed to metasomatic scapolite that is hosted in a range of rock types of various age (c. 1.7-1.5 Ga)

Contrasting composition of metasomatic and metamorphic scapolite in the Eastern Fold Belt, Northwest Queensland, Australia

The Proterozoic Eastern Fold Belt (EFB) of the Mount Isa Inlier, Australia, preserves one of the largest areas of scapolite-rich rock in the world, and is comparable to several other districts of similar age and metallogenic affinity. The close temporal and spatial association between Cl-rich scapolite and Cu-Au miner-alization in the EFB implies that scapolite could be a useful indicator of mineralized systems. The occurrence of metamorphic scapolite and multiple generations of metasomatic scapolite apparently unrelated to Cu-Au mineralization complicate this relationship. However, we propose that scapolite of various generations can be differentiated on textural, chemical and mineralogical grounds, where metamorphic scapolite (marialite; Mas. so) typically contains less Cl and Na and more Ca, Al and C than those derived via metasomatism (Maso.95). Among the metasomatic scapolites, those associated with Cu-(Au) mineralization have higher Cl and Na (Ma>7o). Texturally, metasomatic scapolite fonns as irregular rounded growths, or as subhedral to euhedral vein-fill, as opposed to metamorphic scapolite that typically fanned cauliflower-shaped porphyroblasts. A primary rock control is also evident \Vhere metamorphic scapolite is restricted to calc-silicate rocks (c. 1.7 Ga) as opposed to metasomatic scapolite that is hosted in a range of rock types of various age (c. 1.7-1.5 Ga)

Modeling outflow from the Ernest Henry Fe oxide Cu-Au deposit: implications for ore genesis and exploration

The Ernest Henry Fe oxide Cu–Au (IOCG) deposit (>ca. 1.51 Ga) is hosted by breccia produced during the waning stages of an evolving hydrothermal system that formed a number of tens of metres to a kilometre scale, pre- and syn-ore alteration halos, although no demonstrable patterns have been attributed to fluids expelled through the outflow zones. However, the recognition of a population of hypersaline fluid inclusions representing the ‘spent’ fluids after Cu–Au deposition at Ernest Henry provides the basis to model the geochemical characteristics of the deposit's outflow zones. Geochemical modeling at 300 °C was undertaken at both high and low fluid/rock ratios via FLUSH models involving three host rock types: (1) granite, (2) calc–silicate rock, and (3) graphitic schist. In models run at high fluid/rock ratios, all rock types are essentially fluid-buffered, and produce an albite–quartz–hematite–barite-rich assemblage, although in low fluid–rock environments, the pH, redox, and geochemical character of the host rock exerts a greater influence on the mineralogy of the alteration assemblages (e.g., andradite, Fe–chlorite, and magnetite). Significant sulphide mineralization was predicted in graphitic schist where sphalerite occurred in both low- and high-porosity models, which indicates the possibility of an association between high-temperature IOCG mineralization and lower temperature base metal mineralization. Cooling experiments (from 300 to 100 °C) using the ‘spent fluids’ predict early high-T (300–200 °C) Na-, Ca-, Fe-, and Mn-rich, magnetite-bearing hydrothermal associations, whereas with cooling to below 200 °C, and with progressive fluid–rock interaction, the system produces rhodochrosite-bearing, hematite–quartz–muscovite–barite-rich assemblages. These results show that the radical geochemical and mineralogical changes associated with cooling and progressive fluid influx are likely to be accompanied by major transformations in the geophysical expression (e.g., spectral and magnetic character) of the alteration in the outflow zone, and highlight the potential link between magnetite- and hematite-bearing IOCG hydrothermal systems

Fluid mixing versus unmixing as an ore-forming process in the Cloncurry Fe-Oxide-Cu-Au District, NW Queensland, Australia: evidence from fluid inclusions

Fluid mixing and/or unmixing (including boiling) are thought to be important mechanisms of mineralisation in copper-gold deposits. Detailed fluid-inclusion studies of regional sodic (-calcic) alteration and local mineralisation in the Cloncurry Fe-oxide-Cu_Au District, NW Queensland, suggest that both fluid mixing and unmixing occurred in these giant mineralised hydrothermal systems. In some cases, the primary character of coexisting multisolid, hypersaline brine inclusions and CO2- or vapour-rich inclusions, the latter crosscut by late Ca- and Na-rich fluid inclusions, indicate that fluid mixing probably occurred subsequent to fluid unmixing and finally resulted in Cu_Au mineralisation. However, the relationship between hypersaline brines and CO2, which was believed to result from an unmixing of a magma-derived H2O_CO2_NaCl ± CaCl2 fluid (see [Miner. Depos. 36 (2001) 93] and references therein), is rather complex as some hypersaline brine inclusions obviously predate CO2 inclusions

Iron oxide copper-gold deposits: geology, space-time distribution, and possible modes of origin

Many diverse ore systems are classified together as iron oxide copper-gold (lOCG) deposits based on an empirical definition arising primarily from geochemical features that do not specify tectonic setting, geologic environment, or sources of ore-forming fluid, metals, or other ore components. Such deposits have (1) Cu, with or without Au, as economic metals; (2) hydrothermal ore styles and strong structural controls; (3) abundant magnetite and/or hematite; (4) Fe oxides with Fe/Ti greater those in most igneous rocks and bulk crust; and (5) no clear spatial associations with igneous intrusions as, for example, displayed by porphyry and skarn ore deposits.\ud \ud IOCG deposits commonly have a space-time association with Kiruna-type apatite-bearing oxide Fe ores and many examples of the latter contain sulfide minerals, Cu, and Au. Most IOCG deposits display a broad space-time association with batholithic granitoids, occur in crustal settings with very extensive and commonly pervasive alkali metasomatism, and many are enriched in a distinctive, geochemically diverse suite of minor elements including various combinations of F, P, Co, Ni, As, Mo, Ag, Ba, LREE, and U. Iron oxide Cu-Au systems are numerous and widely distributed in space and time; they occur on all continents and range in age from the present at least back into the Late Archean. In economic terms, the most important ICOG deposits are those the Carajás district, Brazil (Archean, Amazon craton); in the Gawler craton and Cloncurry districts, Australia (late Paleoproterozoic to Mesoproterozoic debated intracratonic or distal subduction-related settings); and in the Juarassic-Cretaceous extended continental margin arc of the coastal batholitic belt in Chile and Peru. IOCG deposits and associated features define distinct metallogenic belts in which other types of Cu and Au deposits are rare or absent. The largest deposits include Salobo, Cristallino, Sossego, and Alemão (Carajás), Olympic Dam (Gawler craton), Ernest Henry (Cloncurry district), and Candelaria-Punta del Cobre and Manto Verde (Chile), and have resources greater than 100 million metric tons (Mt), ranging up to more than 1,000 Mt with metal grades that exceeds those in most porphyry-style Cu ± Au deposits.\ud \ud A comparison of larger and well-described IOCG deposits illustrates the geologic diversity of the class as a whole. They occur in a wide range of different host rocks, among which plutonic granitoids, andesitic (meta)volcanic rocks, and (meta)siliclastic-metabasic rock associations are particularly prominent. Host rocks may be broadly similar in age to the ore (e.g., Olympic Dam, Candelaria-Punta del Cobre, Raul-Condestable) but in other cases significantly predate mineralization such that ore formation relates to a quite separate geologic event (e.g. Salobo, Ernest Henry). Mineralization is interpreted to have occurred over a wide depth range, from around 10km (e.g., several deposits in the Cloncurry district) to close to the surface (e.g., Olympic Dam); where systems have been tilted and exposed in cross section (such a s at Raúl-Condestable in Peru), they can display strongly zoned mineral parageneses. Structural and/or stratigraphic controls are pronounced, with deposits characterically localized on fault bends and intersections, shear zones, rock contacts, or breccia bodies, or as lithology-controlled replacements. \ud \ud Host rocks in the vicinity of orebodies display intense hydrothermal alteration. In the immediate vicinity of the ore, the variable pressure-temperature conditions of alteration and mineralization are reflected in a spectrum of deposits ranging form those in which the dominant Fe oxide is magnetite and alteration is characterized by minerals such as biotite, K-feldspar, and amphibole though to hematite-dominated systems in which the main silicate alteration phases are sericite and chlorite. Where present, Na and Na-Ca alteration tends to be developed deeper or more distal from ore, is more extensive, and commonly predates K-Fe alteration and mineralization. Carbonates are commonly abundant, particularly in assoication with, or postdating, Cu-bearing sulfides that tend to be paragenetically late and postdate high-temperature silicate alteration in the deeper seated deposits. Independent variation in fO2- fS2-(T) conditions during mineralization produced deposits ranging from pyrite-poor examples, with complex Cu mineral associations, including chalcopyrite, bornite, and chalcocite (e.g., Salobo, Olympic Dam), to others in which pyrite and chalcopyrite are the main sulfides (e.g., Ernest Henry, Candelaria).\ud \ud Fluid inclusion evidence suggests that geochemically complex brines, commonly with a carbonic component, were involved in IOCG genesis. However, the ultimate sources of water, CO2, metals, sulfur, and salinity have yet to be well constrained, and it is possible that these components may have different origins from deposit to deposit. Brines and metals may be sourced directly from underlying magmas, indirectly by interaction of magmatic fluids with country rocks or other fluids, or independently through modification of basinal or metamorphic fluids. Ore deposition may primarily involve interaction of voluminous fluid with wall rocks and cooling. However, several studies have emphasized the role of mixing sulfur-poor, metal-rich brines with sulfur-bearing fluids at the site of ore deposition, although characterization of the causative fluids has proven problematic. Uncertainty also exists about the original tectonic settings of several major IOCG districts, and considerably more research is needed before it will be clear whether these deposits are linked by a single family of related genetic mechanisms or whether they can form in a range of fundamentally different geologic environments from fluids of different sources

Stable isotope evidence for magmatic fluid input during large-scale Na–Ca alteration in the Cloncurry Fe oxide Cu–Au district, NW Queensland, Australia

Sodic–calcic alteration is common in mineralized hydrothermal systems, yet the relative importance of igneous vs. basinal fluid sources remains controversial. One of the most extensive volumes of sodic–calcic rocks occurs near Cloncurry, NW Queensland, and was formed by overlapping hydrothermal systems that were active synchronously with emplacement of mid-crustal batholithic granitoids (c. 1.55–1.50 Ga). Altered rocks contain albite–oligoclase, actinolite, diopside, titanite and magnetite. Alteration was localized by: (A) composite veins and breccias containing crystallized magma intimately intergrown with hydrothermal precipitates; (B) intrusions that host setting A veins and breccias; and (C) extensive breccia and vein systems linked to regional fault systems. Isotope analyses of actinolites in settings A and B indicate calculated δ18OH2O (+8.2 to +10.6‰) and variably depleted δDH2O (−130 to −54‰) compared with typical magmatic fluids, whereas those from setting C typically indicate calculated δ18OH2O (+8.0 to +12.8‰) and δDH2O (−29 to −99‰). The lowest δDH2O values are interpreted as representing residual fluids after significant (> 90%) open-system magmatic degassing. Overall the stable isotope, field, geochronological and geobarometric data suggest that these sodic–calcic alteration systems were formed by the episodic incursion of magmatic fluids that underwent minor isotopic modification as a result of varying degrees of interaction with country rocks

The protracted hydrothermal evolution of the Mount Isa Eastern Succession: a review and tectonic implications

Protracted metal and sulfur contributions to the Eastern Succession iron-oxide–Cu–Au (IOCG) province of the Proterozoic Mount Isa Block occurred primarily as a consequence of long-lived fluid fluxes, stimulated by repeated emplacement of voluminous magmas during rifting and thin-skinned convergence cycles. Although there is a direct role for felsic intrusions of the ca. 1530 Ma Williams–Naraku Batholith in hydrothermal ore genesis, these intrusions came at the culmination of protracted metal reorganization in the crust, not as the sole cause, as indicated by geochronology, mineral paragenesis, and the shapes of some orebodies relative to pre-1530 Ma structures. Spatial and geochemical data on mafic rocks suggests that the concentration of copper and gold into some of the mineral deposits involved a significant component of m- to 1000 m-scale remobilization and reworking of early enrichments, formed during basin evolution and initial inversion, by later regional metamorphic and magmatic–hydrothermal fluids. Osborne (eastern domain) and Eloise-type ores (or ore precursors) initially formed during or before the 1600 Ma regional metamorphic peak, by interaction of basinal or early metamorphic fluids with mafic rocks and ironstones, whereas younger oxidised brines released by the Williams/Naraku intrusions at ∼1530 Ma overprinted magnetite ± sulfides at Osborne (western domain) and Starra to produce the presently mined hematite–chalcopyrite ores. CO2 with mantle-like stable isotope character is abundant at all stages of the hydrothermal evolution and is present in high concentrations even in felsic magmas. We thus infer that CO2 was released directly from enriched mantle, or indirectly from mafic magmas, contaminating the process of volatile release from the top of felsic magma chambers and contributing to production of carbonate gangue in orebodies. Ernest Henry, the largest IOCG deposit in the district, remains the best candidate for a true syn-granite magmatic–hydrothermal orebody. We infer that ore deposition occurred when mantle- or mafic-derived H–C–O–S fluid mixed with saline, oxidised brine derived from the Williams/Naraku Batholith, stripping some ore components (Fe, Sr, Cu) from the local wallrocks, in particular mafic rocks. The protracted hydrothermal evolution is reminiscent of modern back-arcs but the position of the arc during the post-1800 Ma history was hundreds of kilometres east. We propose that mantle enrichment in volatiles occurred around a pre-1840 Ma plate boundary leaving the Kalkadoon–Leichhardt belt as a magmatic arc remnant. This metasomatised mantle was subsequently re-tapped during prolonged distal back-arc spreading and periodic shortening accompanying ongoing magmatism