All posts by John C. Menzies

Research Article Summary: A 485-million-year history of Earth’s surface temperature

Emily J. Judd, Jessica E. Tierney, Daniel J. Lunt, Isabel P. Montañez, Brian T. Huber, Scott L. Wing, Paul J. Valdes, Science. DOI: 10.1126/science.adk3705

An interesting approach to palaeo-temperature modelling – produced by assimilating observational data during the last 485 million years with climate model predictions.

This paper introduces a new statistical estimate of global mean surface temperature (GMST) throughout the Phanerozoic Eon, called PhanDA.  PhanDA was generated using a method known as paleoclimate data assimilation, which statistically integrates geological data with climate model simulations.  This has produced some obvious differences to previous widely circulated models which only use observational data.

PhanDA reconstructed GMST
PhanDA reconstructed GMST for the past 485 million years. Black line shows the median, shading corresponds to the ensemble percentile. Blue rectangles show the maximum latitudinal ice extent, and orange dashed lines show the timing of the five major mass extinctions of the Phanerozoic
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Book Review: Kar-Kar Mitakoodi Traditional Medicinal Plant Uses of the Cloncurry Region

Authors Pearl Connelly & Lynley Wallis

Kar-Kar Mitakoodi Traditional Medicinal Plant Uses of the Cloncurry Region

Purchase:  Mitakoodi Traditional Medicinal Plant Uses of the Cloncurry Region can be purchased on-line 
Most photos are the copyright of Pearly Connelly & Lynley Wallis

The country around Cloncurry comprises the traditional lands of the Mitakoodi People. In this book, Mitakoodi Elder Pearl Connelly teams up with archaeologist Lynley Wallis to provide an overview of the local plants that are used to treat a range of ailments and illnesses. Drawing on available botanical, ethnohistorical and ethnographic accounts, and exploring how other Aboriginal groups also use these same plants, this book provides an excellent introduction to medicinal plant uses in the local region.

Kar Kar details more than 30 native plants that are still used by Aboriginal peoples in Australia and the following is a summary of the introduction and a couple of examples of specific species.  If you are heading into the Cloncurry region then get a copy of this wonderful book.

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Australian Aboriginal Diet – A Model for a Modern Diet?

This post does NOT contains images of deceased Australian Aboriginals – some Australian Aboriginal people find seeing the images and or hearing names of the deceased disturbing as it may disturb that person’s spirit.

Australian Aboriginals were hunter gatherers surviving on “Bush Tucker” and photographs of traditional tribal groups in the 1800s showed that they were impressively muscular, toned and lean. 

The Aboriginal diet consisted of upwards of 6,000 indigenous herbs (Eastwood, 2012), spices, vegetables, animals, birds, reptiles, insects, fruits and flowers (Mooney, 2015). Flora that was consumed in the Indigenous diet included seeds, peppers, fruits, citrus, berries, and more. Mountain pepper, bush tomatoes, muntries, lemon myrtle, wattle-seed, native pepper berries, native mint and honey are just some of the native flora that gave flavour to Indigenous food (Eastwood, 2012).

The main source of protein was the abundant and varied Australia wildlife including  Kangaroos, Wild Turkeys, Possums, Emus, Anteaters, Lizards and Snakes and fish and shellfish along the coast and in rivers.

For 40,000-50,000 years, plants played a supplementary role in the diet of Australian Aboriginal (AA) hunter-gatherers. Recent insights into nutrient composition and physiological effects of AA foods contribute to the debate on the ‘prudent’ diet and human evolution. A 1998 study by Brand-Miller and Holt evaluated over 800 Aboriginal plant foods, comparing them with modern cultivated foods. Their findings are summarized below.

  • A typical 12,500 kJ/3000 kcal diet was characterized as follows
    • Energy contribution from plants ~20-40%
    • Protein: 22-44 g
    • Fat: 18-36 g
    • Carbohydrate: 101-202 g
    • Fiber: 40-80 g
    • Vitamin C: 90-180 mg
  • Composition of the Traditional AA Diet:
    • Low in carbohydrates, especially starch
    • High in dietary fiber
  • Carbohydrate Sources:
    • Over half from sugars derived from fruit and honey
  • Low Glycemic Index:
    • Traditional Carbohydrate foods had a low glycemic index
    • Resulting in a relatively low demand for insulin secretion
  • Potential Protective Effect:
    • Low demand for insulin secretion may have protected AA from genetic predisposition to insulin resistance.
    • Potential prevention of consequences like non-insulin-dependent diabetes mellitus, coronary heart disease, and obesity.
  • Dietary Pattern and Lifestyle:
    • The dietary pattern and active lifestyle of recent hunter-gatherers like AA could serve as a reference standard for modern human nutrition.
    • It may act as a model for defense against diseases of affluence.

Australian Aboriginal Model Diet

While there is little nutritional information on traditional foods, I have created a diet model based upon Kangaroo and insect meats, seeds and berries. It consists of 450g of roast kangaroo, 50g of Witchetty Grubs, 325g of seeds and 250g of berries for a target caloric intake of ~3,000 kCal reflecting an active lifestyle using 50% of BMI calories. This results in a diet consisting by caloric intake of 30% protein, 22% carbs and 48% fat with more than 100g of fiber. On this basis and considering their active lifestyle they would have been very healthy with intentional and unintentional injury being the major health risks.

Below is the dietary model for the Australian Aboriginal before the arrival of Europeans.

This model diet would have resulted in near optimal potassium, Omega 3, fat, carbs and iron but likely low sodium by modern standards. As with desert dwelling native peoples of SW Africa, Australian Aboriginals would have adapted to a low sodium diet.

Australian Aboriginals may have adapted over a long period of time to a low GI diet resulting in efficient and sparing insulin production.  Many Australian Aboriginals now suffer from the health effects of a high carbohydrate diet and diabetes has become a serious issue. It is possible that they are now genetically predisposed to excessive insulin production from a diet which is now high in refined carbohydrates. 

Interestingly many in the west are now pursing not dissimilar low GI diets but likely with significantly less fibre.  I suspect that cancer rates in Australian Aboriginals were likely very low before the arrival of Europeans. 

Eastwood, R. (2012). Australian Cookbook- Outback Bushtucker (pp. 1-5). Wingback Books.

Australian Aboriginal Diet – A Model for a Modern Diet?

WARNING: This post contains images of deceased Australian Aboriginals – some Australian Aboriginal people find seeing the images and or hearing names of the deceased disturbing as it may disturb that person’s spirit.

Australian Aboriginals were hunter gatherers surviving on “Bush Tucker” and photographs of traditional tribal groups in the 1800s showed that they were impressively muscular, toned and lean. 

The Aboriginal diet consisted of upwards of 6,000 indigenous herbs (Eastwood, 2012), spices, vegetables, animals, birds, reptiles, insects, fruits and flowers (Mooney, 2015). Flora that was consumed in the Indigenous diet included seeds, peppers, fruits, citrus, berries, and more. Mountain pepper, bush tomatoes, muntries, lemon myrtle, wattle-seed, native pepper berries, native mint and honey are just some of the native flora that gave flavour to Indigenous food (Eastwood, 2012).

The main source of protein was the abundant and varied Australia wildlife including  Kangaroos, Wild Turkeys, Possums, Emus, Anteaters, Lizards and Snakes and fish and shellfish along the coast and in rivers.

Brisbane River Indigenous inhabitants, 1890’s. Source: John Oxley Library

For 40,000-50,000 years, plants played a supplementary role in the diet of Australian Aboriginal (AA) hunter-gatherers. Recent insights into nutrient composition and physiological effects of AA foods contribute to the debate on the ‘prudent’ diet and human evolution. A 1998 study by Brand-Miller and Holt evaluated over 800 Aboriginal plant foods, comparing them with modern cultivated foods. Their findings are summarized below.

  • A typical 12,500 kJ/3000 kcal diet was characterized as follows
    • Energy contribution from plants ~20-40%
    • Protein: 22-44 g
    • Fat: 18-36 g
    • Carbohydrate: 101-202 g
    • Fiber: 40-80 g
    • Vitamin C: 90-180 mg
  • Composition of the Traditional AA Diet:
    • Low in carbohydrates, especially starch
    • High in dietary fiber
  • Carbohydrate Sources:
    • Over half from sugars derived from fruit and honey
  • Low Glycemic Index:
    • Traditional Carbohydrate foods had a low glycemic index
    • Resulting in a relatively low demand for insulin secretion
  • Potential Protective Effect:
    • Low demand for insulin secretion may have protected AA from genetic predisposition to insulin resistance.
    • Potential prevention of consequences like non-insulin-dependent diabetes mellitus, coronary heart disease, and obesity.
  • Dietary Pattern and Lifestyle:
    • The dietary pattern and active lifestyle of recent hunter-gatherers like AA could serve as a reference standard for modern human nutrition.
    • It may act as a model for defense against diseases of affluence.

Australian Aboriginal Model Diet

While there is little nutritional information on traditional foods, I have created a diet model based upon Kangaroo and insect meats, seeds and berries. It consists of 450g of roast kangaroo, 50g of Witchetty Grubs, 325g of seeds and 250g of berries for a target caloric intake of ~3,000 kCal reflecting an active lifestyle using 50% of BMI calories. This results in a diet consisting by caloric intake of 30% protein, 22% carbs and 48% fat with more than 100g of fiber. On this basis and considering their active lifestyle they would have been very healthy with intentional and unintentional injury being the major health risks.

Below is the dietary model for the Australian Aboriginal before the arrival of Europeans.

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This model diet would have resulted in near optimal potassium, Omega 3, fat, carbs and iron but likely low sodium by modern standards. As with desert dwelling native peoples of SW Africa, Australian Aboriginals would have adapted to a low sodium diet.

Australian Aboriginals may have adapted over a long period of time to a low GI diet resulting in efficient and sparing insulin production.  Many Australian Aboriginals now suffer from the health effects of a high carbohydrate diet and diabetes has become a serious issue. It is possible that they are now genetically predisposed to excessive insulin production from a diet which is now high in refined carbohydrates. 

Interestingly many in the west are now pursing not dissimilar low GI diets but likely with significantly less fibre.  I suspect that cancer rates in Australian Aboriginals were likely very low before the arrival of Europeans. 

Australian Aboriginals: Source Unknown Circa 1890s

Eastwood, R. (2012). Australian Cookbook- Outback Bushtucker (pp. 1-5). Wingback Books.

Major Advance in Telephone Communications

This article from the Brisbane Courier of Saturday, December 22nd, 1923, puts our modern world of global and near earth communications in perspective – this was a mere 100 years ago.

TELEPHONIC CHAIN. LINKING UP.

FOUR STATES CONNECTED.

SYDNEY, December 21.

There Is now a complete chain of telephone lines along the Australian coast from Mackay, In Queensland, to Port Augusta, In South Australia.

A new trunk line between Sydney and Lismore has just been completed, and conversation is easier than between Sydney and Redfern. Brisbane now talks to Sydney, and Brisbane can talk to Melbourne, but commercial calls are not yet a practical proposition.

However, the lines between Sydney and Melbourne are being tuned up to make this possible The coast line is not used for this, though the main trunk line follows the railway It will be a matter of time only before the four States are linked up. Communication is possible now, but only under difficulties.

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High Sulphidation, Vuggy Silica – Textural Atlas

The atlas has been updated with images from the Onto Deposit in Indonesia courtesy of David Burrows. The Onto deposit currently has an indicated resource of 0.76 billion tonnes (Gt) at 0.93% Cu, 0.56 g/t Au, 5 g/t Ag, and 350 ppm As (7 Mt contained Cu, 13 Moz Au) and an inferred resource of 0.96 Gt at 0.87% Cu, 0.44 g/t Au, 3 g/t Ag and 350 ppm As (8.3 Mt contained Cu, 14 Moz Au). In addition to these resources, an exploration target of 0.6 to 1.7 Gt at 0.4 to 0.7% Cu and 0.2 to 0.3 g/t Au has been delineated in a sur- rounding envelope based on drilling at approximately 200 × 200- to 400 × 400-m centers. Also recent samples are included from the Khvav Project in Cambodia.

Residual vuggy silica clasts in a fine-grained siliceous matrix from the Cliffs Prospect, Khvav, Cambodia.
Onto, Indonesia: Drill hole VHD034 at 845m which was the end of the drill hole in discovery hole VHD034. Last 2-m interval grades 0.6% Cu and 2 g/t Au. Vuggy residual quartz alteration with well-preserved A-B veinlet stockwork in the early porphyry. Not pyrite filling vug space in top left, with covellite filling vugs closer to the pencil. CREDIT: David Burrows

Vuggy silica textures are formed by the dissolution of phenocrysts and entire clasts by hot and strongly acidic fluids that are generated during the cooling and crystallization of near surface intrusive bodies. Vuggy silica is often mineralized but is also a strong indicator of a very active hydrothermal system and epithermal Cu-Au-Ag and porphyry Cu-Au deposits at depth.

Please participate and contribute your photographs!

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Old Moreton Bay Tribes. Their Lost Languages.

Brisbane Courier (Qld. : 1864 – 1933), Saturday 1 December 1923, page 19

By A. MESTON.

Few people have any knowledge of the vast amount of works, reports, and papers that have been written on the anthropology, ethnology, and geological history of the aboriginals of Australia and Tasmania.

Australian Aboriginal party likely in the Brisbane area

Many of the books are rare, and many of the reports and papers are found only in scientific journals not accessible to the general public. Much valuable information is hidden away in the Journal of the Royal Anthropological Institute of Great Britain. Scores of papers, memoirs, and vocabularies are scattered over works of travel and exploration, and the trans-actions of scientific societies. About four hundred books and papers are catalogued, but there are not many complete books, and even all those are not standard authorities.

The late Robert Etheridge, junior of the Sydney Museum, in his valuable catalogue issued by the Mines Department of New South Wales when Sydney Smith was Minister, quotes Brough Smyth, J. D. Woods, G. Taplin, Fison and Howitt, William Ridley. Captain Sadleir, E. M. Curr, James Bonwick, J Dawson, and Dr. Topinard as among the best of the writers.

He omits one of the most important of all, L. E. Threlkeld, who was 14 years missionary among the blacks of Port Macquarie, and wrote a masterly work on the Awabakal dialect, the most complete of all recorded vocabularies, and the best explanation of the grammatical structure of any Australian dialect.

It was published in 1850. The people who spoke that Awabakal are long since extinct, and there are not many living blacks to-day who can speak much of even the once great Kamilroi, Wiradjerie, and Jucumbah (Yucumbah) dialects of New South Wales. Tribes after tribes have vanished, and their dialects have gone with them into oblivion.

Among the old Moreton Bay tribes there were seven dialects spoken, and they are all practically extinct. In my lifetime I have seen tribe after tribe disappear, one dialect after another become extinct, until there is hardly a soul left of the people who spoke the dialects familiar to me in my youth. The tribes of Moreton, Bribie, and Stradbroke Islands have gone forever, and all that is left of their dialects, presumedly, is what was taken down by me in 1870 and 1874. On Stradbroke Island there are still some half castes and quadrooms who speak part of the old Coobennpil dialect, but with them and even that will disappear, so that white people in the last short period of 30 years have seen whole aboriginal tribes and their languages passing silently away from us, like a series of dissolving views, into Eternity. It seems to me to be a scene so solemn, and tragic, and pathetic, as to be capable of exciting pity in the hardest hearted and serious reflections in the most thoughtless. When the Roman spies found Marius sitting among the ruins of Carthage he said to them. “Some day Rome may be like Carthage!” In some unknown future, where Brisbane stands, may be desolate as the sand dunes of Moreton Island, mighty cities of past ages lie hidden by the sands of the desert.

SOFT AND EUPHONIOUS SPEECH.

And they were so soft and euphonious, those old Moreton Bay dialects, that it was a pleasure to hear them spoken, especially by the women and children Our language is discordant by comparison.

You ask a Moreton Islander, “Where are you going,” and in a soft voice he would ask you “Wanyeegneen yanumba?” You say, “I don’t know,” and he merely replies “wanyeenggam.” You ask him, “Where are all the blacks?” expressed by him as “wanyee dan mah-gee?”

You ask him, “Where is the death adder?” and he would softly say it as “wanyee moonoom.” He called the native bee “cooneeda,” which recalls that beautiful poem of Essex Evans on the “Cymru,” and “the spirit of stern Cuneida, the last of the Brython Kings.” At Sydney rain was banna, and it was rain at Moreton Bay, reappearing as rain again at Cairns. At Moreton Bay the small pathway from the small to the big Bora circle was boreen, and boreen was a small crooked foot track in the Irish Gaelic. At Townsville the word for white was “alba,” pure Latin. Com-parative philology shows a considerable number of aboriginal words in English, Gaelic, Italian, Hebrew, Hindustani, and broad Scottish, in some cases, with exactly the same meaning, but all that proves nothing.

Stanley records “wee” for five in Central Africa, and it was the word for five at Bundaberg and Rockhampton. A word in one dialect may have quite a different meaning in another. At Moreton Bay, one, two, three, four were canyahra, boollah, tiyarra, mahjan. From Townsville to Cooktown canyahra was the crocodile. There was an amazing flexibility in the language ; and an astonishing modification of the verbs by the use of suffixes and affixes, so that one word would express three or four of ours. In the first dialect spoken by me, the Yoocumbah of the Clarence, the generic name of the race was Murri, a man was murri, a young man murriwan, a boy murriwanjin, a woman murri-wanggeen, a girl murriwanggeena.

In the Ahwabah dialect, ahwa was no, ahwa-bah the place where ahwa was no, and also the language itself, while ahwabbakal was the race who spoke that language, and the men of that race, while the women were ahwabbakaleen, the girls ahwabbakaleena. Our language has no such flexibility as that. Their nouns show the nominative, genitive, ablative, dative, accusative cases, and in addition to the remarkable inflection of the verbs they show the indicative, imperative, potential, and subjunctive moods, and past, present, and future tenses.

Usually the adjective followed the noun, as in French and Italian. An Italian, instead of saying a white horse, says “un cavallo bianca,” a horse white. And the aboriginal is as likely to ask where are you going, as you where going, or you going where? The verb is often omitted, especially with the interrogative adverb, such as “minta into ginda-hnya? what you laught at? and not what are you laughing at? If asking a Coobenmpil speaking man of Stradbroke Island to have a drink, I would say to him, “gnaleen yieeba jaleeba maroomba, literally “we together drink good.” A short toast would be simply “jaleeba maroomba,” or “drink good,'” much more euphonious than most of our meaningless toasts.

DIFFICULTY OF TRANSLATING.

To show the effect of translating, and the difficulty of expressing the same sense, I shall give here the Lord’s Prayer in the Coobennpil dialect to show how it reads:

Come down to us: Bulka gnaleeba.
We do here what they do up there: Yaganna gnallee noonam tamanna,
To-day give us bread: Bayann, woodya gnalleegannoo binggin
Forgive us this time: Wallee gnalleegnanna banmal,
Don’t lead us to do wrong: Wallee gnalleegnanna waleemal,
Take us away from bad: Yandeegee gnalleegnanna waleenjee.
You are great, all is yours: Gnareeba nanamm, cooroomba beera, Coobaggoolabbo! (For ever!)

The reader is asked to pronounce the g and u always hard and short, as in gun.

Very surprising is the difference of the dialects of Moreton and Stradbroke Islands, separated only by a narrow channel, which probably had no existence at all 200 years ago ; but it is well to re-member that the Rhine, in Germany, and the Tweed, in Scotland, separate two languages, that there are four different languages in the small island of Britain Welsh, English, Gaelic, Lowland Scottish, really old Saxon, and a number of uncouth English dialects.

DIFFERING DIALECTS.

The aboriginal dialects differed widely from each other, some having a much more copious vocabulary than others, and, as in the case of ourselves, the average man only spoke a fraction of his own language, which not being fixed by printing and books, was frequently changing. Even literature fails to fix a language, for the English of Chaucer and Spenser would not be understood by the Australians of to-day.

On Moreton Island the aboriginal race was Mahgee, and on Stradbroke Mullara. North of Caboolture and thence to the Mary River, the race was Dahn. A fire-stick at Brisbane was chucabbil, at Stradbroke tucabbin, at Moreton weeramm, and north of Caboolture carba. At grand corroborees, great fights, or feasts of the Bunya, the various tribes camped apart, but there was a certain volapuk dialect by which tribes speaking different dialects could understand each other. In ordinary conversation today among the white race the average man or woman does not use more than from 100 to 200 words. No civilised man knows half of his own language. Usually an aboriginal could speak his own language, and the two adjoining dialects. As with us, there were some who were much more complete linguists and eloquent speakers than the others. If a Brisbane black took a Nerang Creek woman for a wife, she had to learn Wacca, and the children were brought up in that dialect, but they usually learned the language of the mother. If a boy or girl had a tendency to talk in a loud or harsh voice, loud calls of “no more black cockatoo,” or “no more leatherhead,” or “too much kookaburra,” or “you talk like a crow,” killed the harsh voice with ridicule, and ridicule with them was a deadly weapon. At the camp fire, riddles were a favourite pastime, and some were very ingenious. On Stradbroke, among those recorded by me, was one where a man had a boy who was a mischievous little rascal. His father had made a new boomerang, and one day when going out hunting he put it up in the fork of a tree, and warned his son not to touch it. Of course, the son assured him that nothing was farther from his thoughts, and when dad was out of sight he promptly climbed the tree, got the boomerang, walked down to the beach, and threw it away towards the West. The boomerang went away out of sight, and did not return for about four weeks! Great guessing in the camp, and sarcastic suggestions that the narrator was a splendid liar, until he explained that the boomerang was “Gillenn,” the new moon, and then there was hilarious laughter.

There were orators among them, eloquent men, capable of highly dramatic declamation, and they were listened to with rapt attention, in profound silence. There were no cheers, interjections, or in-terruptions. Ridley tells of a wonderful speech he heard from an old Kamilroi black on the wrongs of his race, and I heard two unforgettable orations on the same subject.

In voice and gesture savage Nature, spoke, and from their eyes the gladiator broke.

And now that ancient race of hunters and athletes, their soft melodious speech, their picturesque customs, their interesting and original weapons, their songs, dances, and traditions, are soon to be hidden in the closing mists of a dead, forgotten past, apparently the ultimate doom of all humanity, for such is the inexorable “Testimony of the Rocks.”

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Fluid flow Model for the Mt Isa Cu and Pb-Zn-Ag Mineralization

Ben Andrew, Senior Geologist at Mt Isa Mines submitted a captivating PhD thesis (Andrews, B.S., 2020) in 2020 on alteration at Mt Isa and its implications for fluid flow of the hydrothermal fluid that formed the world class Cu and Pb-Zn-Ag orebodies.  Here we summarize some of his δ18O results.

Spatial interpolation of δ18O values at Mount Isa projected on to the Paroo Fault surface (Andrews, 2020)

Introduction

The Mount Isa Pb-Zn-Ag and Cu deposit are situated in Northwest Queensland, specifically within the Mount Isa Inlier, a geological region that encompasses one of the most extensive areas of Proterozoic crust preserved in the Australian continent, covering approximately 61,000 square kilometers.

The deposit itself comprises copper mineralization hosted within veins and breccias, along with strata-bound lenses of lead, zinc, and silver mineralization arranged in an en-echelon fashion. These distinct orebodies are spatially associated but remain independent.

Prior to any mining activities, the deposit was estimated to contain substantial resources, with 255 million tonnes at 3.3% copper, and 150 million tonnes at 7% zinc, 6% lead, and 150 grams per ton of silver.

Moreover, the Isa valley, delineated as the Leichardt River catchment area upstream of Lake Moondarra, is home to other world-class Pb-Zn-Ag deposits at George Fisher and Hilton. These deposits also exhibit some copper mineralization of sub-economic significance. Notably, all economic base metal mineralization discovered within the Isa valley is confined within the Urquhart Shale, a geological formation characterized by its carbonaceous, dolomitic, siltstone, and shale within the Mount Isa Group.

A cross-sectional view at 36,600 meters north illustrates the relationship between the 650, 3000, and 3500 copper orebodies and basement geology. It highlights the distribution of copper mineralization, visible mineral alteration, and the lead, zinc and silver deposits. (After Andrews,, 2020)

The Mount Isa deposits have been under continuous mining operations since their discovery in 1923 and have a rich history of extensive research efforts. However, the enduring geological debate concerning Mount Isa revolves around the fact that a single mine yields low-copper ore from an enormous stratiform lead-zinc deposit, alongside low-lead-zinc ores from a world-class breccia-hosted copper deposit, all occurring within a remarkably small area of less than 1 km in both vertical and horizontal dimensions.

This distinctive spatial association of world-class base metal deposits has generated significant contention regarding the genetic model of the Mount Isa Pb-Zn-Ag and Cu deposits. Specifically, there has been ongoing controversy regarding the timing of the formation of the two deposits and whether the orebodies are syngenetic (formed during sedimentation) or epigenetic (formed during later deformation).

Oxygen Isotope Study

In 2020, Andrews conducted a comprehensive investigation of the extensive isotopic alteration linked to copper mineralization at Mount Isa. This research extended previous isotopic studies and exploration initiatives by constructing a three-dimensional spatial interpolation of stable carbon and oxygen isotope data. It involved a comparison of outcomes obtained from one-dimensional reactive transport models with δ18O alteration patterns observed at Mount Isa. The primary goal was to gain insights into the hydrothermal fluid flow patterns within the system, including the identification of fluid flow pathways and fluid input zones.

Spatial interpolation of δ18O values at Mount Isa projected on to the Paroo Fault surface (Andrews, 2020)

Andrews, 2020 interpolated the δ18O and reports a number of plans and sections.  Previous studies have inferred that the Paroo Fault played a critical role in focusing hydrothermal fluid flow during the deposition of copper mineralization.  The most compelling representation of the data is a 3D view of the δ18O value interpolation using the Paroo Fault as a reference surface (see image above). 

This reveals that there is a nested set of isotope surfaces with consistent spatial variations. It reveals that all the rock formation in the hanging-wall of the Paroo Fault exhibit δ18O values below 14‰. However, the above figure shows discrete, coherent zones of carbonate rocks with δ18O values less than 10‰.  These zones are oriented along NW-SE and N-S trends that extend a maximum length of 1500 m. A zone with δ18O values between 10 and 11‰ confirms these trends and highlights a further subtle NE-SW trend. Both NW-SE and NE-SW trends broadly transgress the stratigraphy of the Mount Isa Group, which predominantly strikes N-S within the Isa valley.

Andrews, 2020 concludes that mapping δ18O values on the Paroo Fault identifies zones of δ18O -depletion associated with fluid input zones. Zones of intense δ18O -depletion coincide with the axis of D3 folds in the basement contact and basement lineaments that potentially dilated during NW-SE directed, D4 compression, both of which are proposed to have focused fluid flow from basement rocks to sites of copper mineralization in metasediments.

Fluid Flow Model

Diagram illustrating the role of structural elements at Mount Isa in focusing of hydrothermal fluid flow responsible for δ18O-depletion patterns (Andrew, 2020)

Andrews, 2020 suggests that large-scale patterns of oxygen isotope alteration in carbonates at Mount Isa can be explained by propagation of a δ18O reaction front during the infiltration of isotopically light fluid into unaltered metasediments of the Mount Isa Group and progressive isotopic exchange between these two oxygen reservoirs.

Reactive transport theory dictates that the fluid buffered region of the hydrothermal system is located upstream of the reaction front, adjacent to the start of the fluid flow pathways. As such, Andrew, 2020 interprets the fluid flow responsible for δ18O depletion in carbonate rocks at Mount Isa to have occurred in a predominantly upward direction from the Paroo Fault and that the data precludes south to north directed flow of hydrothermal fluids. Further, zones of intense δ18O depletion are closely associated with copper mineralisation adjacent to the Paroo Fault and δ18O values less than 10‰ around 37,000 mN strongly suggest the 3500-copper orebody sits adjacent to a fluid inlet.

δ18O values also suggest that fluid flow from the underlying basement rocks toward sites of mineralization in the overlying metasediments is concentrated in the area extending from the center of the 1100 orebody towards the SSE, likely attributed to the Bernborough Fault. Additionally, the formation of other orebodies is believed to have been influenced by various structural features, such as zones of dilation within the hinge of NE-trending D3 folds along the basement contact and N-S striking master faults and tensile linking structures. It is also suggested that zones of dilation beneath synformal inflections on the basement contact may have facilitated the downward movement of metasediment-equilibrated fluids into the underlying Eastern Creek Volcanics.

Video of supplementary material from Andrew, B., 2020 PhD Thesis

Reference

Andrew, B.S., 2020, Recognizing cryptic alteration surrounding the Mount Isa Copper Deposits: implications for controls on fluid flow, and mineral exploration, PhD Thesis, University of Waikato.

Tracing Mantle-Oxygen Fugacity Changes Through the Great Oxidation Event: Insights from Apatite Inclusions in Brazilian Igneous Zircons

Moreira, H., Storey, C., Bruand, E. et al. Sub-arc mantle fugacity shifted by sediment recycling across the Great Oxidation Event. Nat. Geosci. 16, 922–927 (2023). https://doi.org/10.1038/s41561-023-01258-4

Substantial accumulation of free oxygen in the atmosphere occurred between ~2.45 and 2.20 billion years ago , with permanent atmospheric oxygenation commencing between 2.3 and 2.2 Ga. This period is known as the Great Oxidation Event (GOE) and marks the most dramatic change in Earth’s surface chemistry and habitability. However, it remains unclear if these major atmospheric changes affected the amount of free or chemically available oxygen in the mantle and, consequently, the redox state of mantle-derived magmas. In the modern Earth, considerable amounts of surface-oxidized components infiltrate the mantle via slab fluids and subducted sediments, ultimately influencing the oxidation state of the mantle wedge and arc magmas.

Palaeoproterozoic magmatic transition.

a, Zircon U–Pb ages versus 176Hf/177Hf(t) ratios (expressed as ɛHf(t) values relative to chondrite at the time of crystallization t). Zircons from TTG magmas (n = 31) have significantly positive ɛHf(t), whereas zircons from the sanukitoid magmas (n = 33) are near the CHUR. A crustal evolution line links both suites of rocks to a DM melting event at ~2.5 Ga.
b, Zircon 18O/16O ratios (expressed as δ18O relative to Vienna Standard Mean Ocean Water) show that the basaltic crust was hydrothermally altered at high temperature (~4.5‰) before generating TTG magmas at 2.35 Ga and before remelting in the metasomatized mantle wedge at 2.13 Ga. The latter event generated sanukitoids that have zircons with heavier oxygen (~6.5‰). Individual error bars in a and b are shown at 2 standard errors.
c, Tectonic model for the generation of magmas in the Palaeoproterozic pre- and post-GOE peak. SCLM stands for subcontinental lithospheric mantle.

Mantle oxygen fugacity ( fO2) probably changed in the early Earth as a result of metallic Fe retention during core formation and further homogenization, but subsequent variations through time are debatable. The mantle fO2 is either described as largely unchanged or overall having a near-constant rate of increase through time.

Continue reading Tracing Mantle-Oxygen Fugacity Changes Through the Great Oxidation Event: Insights from Apatite Inclusions in Brazilian Igneous Zircons

A Pioneer’s Recollections – Part 2

Queensland’s Early Days
BY C. Duncan Laidley
Brisbane Courier (Qld. : 1864 – 1933), Saturday 27 October 1923, page 19

I find it most interesting to read the Brisbane Courier from 100 years ago on a Saturday morning. It brings into stark relief the modern world, that which remains much the same and that which has evolved beyond belief in such a short period of time. Here is a transcription of the recollections of Duncan Laidley who as a 9 year old arrived in Sydney, Australia in January 1842 after a 4-5 month voyage. It should be noted that the discussion of our Aboriginal brothers and sisters may not reflect modern sensitivities.

In this article Mr. Duncan, who is 90 years of age, tells of the Brisbane of 66 years ago, and of his experiences at Bald Hills, Ipswich, Mary borough, Laidley, and other places.

Carseldine’s General Store in Bald Hills in the late 1890’s. James Carseldine open the store in 1969 and his residence is to the right . Courtesy Kris Herron
Continue reading A Pioneer’s Recollections – Part 2