Creationism in Crisis - How We Know Earth is 4.5 Billion Years Old.

A groundbreaking discovery: how we found remnants of Earth’s primordial crust near Perth

I frequently write articles that report on events that happened long before creationist mythology says the Universe was magicked up out of noting with some magic words spoken in a language that no-one spoke by a magic man who had self-assembled out of nothing according to a design it made before it existed.

This probably has creationists scratching their heads trying to think of reasons why the science is wrong because it doesn't fit their preferred mythology. The simple explanation which seems too hard for creationists to grasp is that there is nothing wrong with the science; what's wrong is the mythology they're trying to bend the evidence to fit into.

Like trying to force the Pacific Ocean into a teacup and blaming the teacup for being the wrong shape.

The simple reason that so much of the history of the Universe and of Earth and life on it happened before the mythical 'Creation Week', is that is so much more time for it to have happened in, than there is in the 10,000 years since. In fact, 99.99767% of the history of Earth happened before creationism's mythical 'Creation Week' because Earth is 4.5 billion years old, give or take a few million years.

To put that into perspective, imagine the history of the Earth as a year; land plants didn't evolve unto a month ago, dinosaurs made their appearance two weeks ago and all of human history has happened in the last half an hour. A sobering thought is that on that scale a human life lasts about half a second.

So, how do we know how old Earth is?

The secret is hidden inside crystals of zircon which are themselves embedded in grains of titanite that protect them from environmental changes that could give false dates. This technique gives incredibly accurate dates since there a few, if any, ways in which contamination or leakage can distort the ratios of the isotopes involved:

Remind me how zircons are used in geochronology, and why zircons embedded in titanite grains give a more accurate date, please. Zircons are valuable in geochronology due to several key properties:

1. Uranium-Lead Dating: Zircons (ZrSiO₄) can incorporate uranium (U) atoms into their crystal structure but exclude lead (Pb) when they form. Over time, the uranium atoms decay into lead isotopes (U-238 to Pb-206 and U-235 to Pb-207) at known rates. By measuring the ratios of uranium to lead isotopes in a zircon crystal, geologists can determine the age of the crystal. This method is highly reliable because it involves two separate decay chains, providing a cross-check.
2. Resistance to Alteration: Zircons are chemically and physically robust, resistant to weathering, and high-temperature metamorphism. This durability means they can survive geological processes and provide age information that is less likely to be reset by subsequent events.
3. Containment of Original Material: Zircons often contain inclusions of other minerals and sometimes even preserve tiny amounts of the original magma or fluid in which they formed. These inclusions can provide additional information about the conditions at the time of zircon formation.

Importance of Zircons in Titanite Grains

When zircons are embedded in titanite (CaTiSiO₅ - calcium titanium silicate) grains, they can provide even more accurate dates for several reasons:

1. Protection from Alteration: Titanite can act as a protective barrier around zircons, shielding them from alteration and resetting during subsequent geological events. This protection helps preserve the original uranium-lead ratios in the zircons, ensuring more accurate dating.
2. Enhanced Contextual Information: The presence of zircon within titanite grains provides additional context about the geological history of the sample. Titanite is often associated with specific types of metamorphic and igneous processes. By dating zircons within titanite, geologists can correlate the timing of zircon crystallization with these specific processes.
3. Reduction of Lead Loss: In some cases, zircons might lose lead over time, leading to inaccurate age calculations. Titanite encapsulation can minimize this lead loss, preserving the original isotopic compositions and improving the precision of age determinations.

Overall, zircons are critical in geochronology because of their ability to preserve ancient isotopic information, and their embedding in titanite grains provides an additional layer of protection and contextual information, leading to more accurate and reliable dating.

What are the half-lives of U-238 and U-235?

The half-lives of uranium isotopes are as follows:

1. Uranium-238 (U-238): The half-life of U-238 is approximately 4.468 billion years (4.468 x 10⁹ years).
2. Uranium-235 (U-235): The half-life of U-235 is approximately 703.8 million years (7.038 x 10⁸ years).

These long half-lives make uranium isotopes particularly useful for dating geological materials over a wide range of ages.

What are the decay chains for the two isotopes of uranium?

The decay chains for the two uranium isotopes, U-238 and U-235, are as follows:

Decay Chain of U-238 (Uranium-238)

The U-238 decay chain, also known as the uranium series is:

1. Uranium-238 (U-238) decays to
2. Thorium-234 (Th-234) (half-life: 24.1 days) decays to
3. Protactinium-234 (Pa-234) (half-life: 1.17 minutes) decays to
4. Uranium-234 (U-234) (half-life: 245,500 years) decays to
5. Thorium-230 (Th-230) (half-life: 75,380 years) decays to
6. Radium-226 (Ra-226) (half-life: 1,600 years) decays to
7. Radon-222 (Rn-222) (half-life: 3.823 days) decays to
8. Polonium-218 (Po-218) (half-life: 3.10 minutes) decays to
9. Lead-214 (Pb-214) (half-life: 26.8 minutes) decays to
10. Bismuth-214 (Bi-214) (half-life: 19.7 minutes) decays to
11. Polonium-214 (Po-214) (half-life: 164.3 microseconds) decays to
12. Lead-210 (Pb-210) (half-life: 22.3 years) decays to
13. Bismuth-210 (Bi-210) (half-life: 5.01 days) decays to
14. Polonium-210 (Po-210) (half-life: 138.4 days) decays to
15. Lead-206 (Pb-206), which is stable.

Decay Chain of U-235 (Uranium-235)

The U-235 decay chain, also known as the actinium series is:

1. Uranium-235 (U-235) decays to
2. Thorium-231 (Th-231) (half-life: 25.52 hours) decays to
3. Protactinium-231 (Pa-231) (half-life: 32,760 years) decays to
4. Actinium-227 (Ac-227) (half-life: 21.772 years) decays to
5. Thorium-227 (Th-227) (half-life: 18.72 days) decays to
6. Radium-223 (Ra-223) (half-life: 11.43 days) decays to
7. Radon-219 (Rn-219) (half-life: 3.96 seconds) decays to
8. Polonium-215 (Po-215) (half-life: 1.78 milliseconds) decays to
9. Lead-211 (Pb-211) (half-life: 36.1 minutes) decays to
10. Bismuth-211 (Bi-211) (half-life: 2.14 minutes) decays to
11. Thallium-207 (Tl-207) (half-life: 4.77 minutes) decays to
12. Lead-207 (Pb-207), which is stable.

These decay chains involve multiple steps of alpha and beta decay, leading to the formation of stable lead isotopes (Pb-206 for U-238 and Pb-207 for U-235).

Is there any other way that Pb-206 and Pb-207 can get into the zircon crystal matrix?

While the primary means by which Pb-206 and Pb-207 are incorporated into zircon crystals is through the radioactive decay of uranium isotopes (U-238 and U-235, respectively), there are a few other mechanisms by which lead can be present in zircon crystals:

1. Initial Lead Incorporation: When zircon crystals initially form, they might incorporate a small amount of lead directly from the surrounding magma. However, this initial or "common" lead is typically very minimal because zircons preferentially incorporate uranium over lead due to the differences in their ionic radii and charge.
2. Radiogenic Lead Migration: Over long geological timescales, radiogenic lead (Pb-206 and Pb-207) produced within the zircon crystal might migrate within the crystal lattice or even be lost to some extent if the crystal has been subjected to high temperatures or metamorphic events. This migration can sometimes result in lead being found in different parts of the crystal than where it was originally produced.
3. Secondary Processes: During geological events such as metamorphism or hydrothermal activity, lead from external sources can be introduced into zircon crystals. However, zircons are quite resistant to such alterations, making this a less significant source of lead compared to primary uranium decay.

To address these potential sources of non-radiogenic lead, geochronologists use several techniques:

• Concordia Diagrams: These plots compare the ratios of U-238 to Pb-206 and U-235 to Pb-207. Concordant data points (those that lie on the concordia curve) indicate a closed system with minimal lead loss or gain. Discordant points can be analyzed to understand lead loss or gain events.
• Chemical Abrasion and Air Abrasion: Techniques such as chemical abrasion (leaching zircons in acid) and air abrasion are used to remove parts of the zircon that might have been altered or affected by lead loss.
• Isochron Methods: Isochron dating involves measuring isotopic ratios from multiple grains or parts of grains to identify and correct for the presence of non-radiogenic lead.

By employing these methods, geochronologists can accurately determine the age of zircon crystals and mitigate the effects of any extraneous lead.

How this dating method was used is the subject of an article in The Conversation by Chris Kirkland, Professor of Geochronology, Curtin University, Perth, Western Australia. His article is reprinted here under a Creative Commons license, reformatted for stylistic consistency:

Published: June 20, 2024 11.09am BST

A groundbreaking discovery: how we found remnants of Earth’s primordial crust near Perth

Lukas Gojda / Shutterstock

Chris Kirkland, Curtin University

Our planet was born around 4.5 billion years ago. To understand this mind-bendingly long history, we need to study rocks and the minerals they are made of.

The oldest rocks in Australia, which are some of the oldest on Earth, are found in the Murchison district of Western Australia, 700 kilometres north of Perth. They have been dated at almost 4 billion years old.

In a new study, we have found evidence of rocks of a similar age near Collie, south of Perth. This suggests the ancient rocks of Western Australia cover a far greater area than we knew, buried deep in the crust.

The ancient continental crust

The ancient crust of Australia is crucial for understanding the early Earth, because it tells us about how the continental crust formed and evolved.

Continental crust forms the foundation of landmasses where humans live, supporting ecosystems, and providing essential resources for civilisation. Without it there would be no fresh water. It is rich in mineral resources such as gold and iron, making it economically significant.

However, exploring the ancient continental crust is not easy. Most of it is deeply buried, or has been intensely modified by its environment. There are only a few exposed areas where researchers can directly observe this ancient crust.

To understand the age and composition of this hidden ancient crust, scientists often rely on indirect methods, such as studying eroded minerals preserved in overlying basins, or using remote sensing of sound waves, magnetism or gravity.

However, there may be another way to peer into the deep crust and, with luck, even sample it.

Dragging crystals up from the depths

The crust of our planet is frequently cut by dark fingers of magma, rich in iron and magnesium, which can stretch from the upper crust all the way down to Earth’s mantle. These structures, known as dykes, can come from depths of at least 50 kilometres (much deeper than even the deepest borehole, which stretches a mere 12 kilometres).

These dykes can pick up tiny amounts of minerals from the depths and transport them all the way up to the surface, where we can examine them.

Dykes in Norway cutting into older layered sandstone rocks.

Cato Andersen/Mapillary, CC BY-SA

In our recent study, we have uncovered evidence of ancient buried rock by dating grains of zircon from one of these dykes.

Zircon contains trace amounts of uranium, which over time decays to lead. By precisely measuring the ratio of lead to uranium in zircon grains, we can tell how long ago the grain crystallised.

This method showed that the zircon crystals from the dyke date back 3.44 billion years.

Titanite armour

The zircons are encapsulated in a different mineral, called titanite, which is more chemically stable than zircon in the dyke. Think of a grain of salt, trapped inside a hard-boiled sugar sweet, dropped into a cup of hot tea.

Microscope image of titanite grain with zircon crystals trapped inside and protected. The scale bar in the right bottom of image is 100 microns, about the width of a human hair.

C.L. Kirkland

The stability of the titanite armour protected the ancient zircon crystals through changes in the chemical, pressure and temperature conditions as the dyke travelled upward. Unshielded zircon crystals in the dyke were strongly modified during the journey, obliterating their isotopic records.

However, the grains armoured in titanite survived intact to provide a rare glimpse into Earth’s early history.

The dyke, itself dated to around 1.4 billion years old, has offered up a unique window into ancient crust that would otherwise have remained hidden. We also found similar ancient zircon grains further north in sand from the Swan River, which runs through Perth and drains the same region, further corroborating the age and origin of these ancient materials.

Cross-section of the crust south of Perth showing dykes picking up 3.4 billion-year-old zircon from depth and bringing it to the surface. The inset zoom-in shows the armouring of this ancient zircon by a shield of the mineral titanite.

C.L. Kirkland

The results extend the known area of ancient crust, previously recognised in the Narryer area of the Murchison district.

One reason it’s important to understand the deep crust is because we often find metals at the boundaries between blocks of this crust. Mapping these blocks can help map out zones to investigate for mining potential.

Remnants of deep time

So next time you pick up a rock and some mineral grains rub off on your hand, spare a thought for how long those grains might have been around.

To come to grips with the time scale, imagine the history of our planet was a year long. Earth formed from swirling dust 12 months ago. Any handful of sand you pick up around Perth will contain a grain or two from about ten months ago. Most of Australia’s gold formed seven months ago, and land plants arrived only one month ago.

Two weeks ago, dinosaurs showed up. All of humanity has come in the past 30 minutes. And you? Soberingly, on this scale, your life would last about half a second.
Chris Kirkland, Professor of Geochronology, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Published by The Conversation.
Open access. (CC BY 4.0)

Professor Christopher Kirkland was lead author in an open access paper in the journal Communications Earth & Environment which provides more technical detail and background to the research:

Abstract
Deep geology of ancient continental crust can be difficult to access, with direct observation restricted to limited exposures. The age and composition of hidden geology can be gleaned from indirect isotopic modelling or via detrital minerals within overlying basins. Here we present an alternative, where direct grain sampling of ancient components within the South West Terrane, Yilgarn Craton, by a Proterozoic dyke evidences deep intact, or detritus from, Paleoarchean crust. U–Pb geochronology on this dyke reveals c. 3440 Ma zircon inclusions within titanite. This zircon was protected from overprinting fluids that obliterated unshielded crystals. Similar ancient zircon is present within recent sediment from the Swan-Avon river, which drains the terrane. The most parsimonious interpretation is that the dyke is 1390 Ma. Sequential overprinting is also recorded, with titanite preserving primary crystallization and c. 1000 Ma Pinjarra Orogeny-related overprinting. In contrast, apatite preserves c. 210 Ma ages, correlated with denudation of sedimentary cover.

Introduction
The likelihood of metamorphic overprinting increases with age, with many of our planet’s most ancient rocks now pervasively modified by later geological processes¹. Specifically, many ancient mafic rocks are now amphibolites, reflecting the metamorphic redistribution of water. Dating the formation age for the protolith of amphibolites is notoriously difficult, due to the conversion of the primary mineralogy to phases that are more stable under subsequent temperature, pressure, and chemical conditions, and the general lack of primary zircon. The result of such overprinting processes is the variable loss of isotopically defined precursor age information. Nonetheless, magmatic dykes, converted to amphibolites, may retain an informative refractory xenocrystic cargo from deeper crustal levels or indeed the upper mantle, entrained on the primary magma’s emplacement pathway^2,3.

Western Australia hosts an important archive of early Earth crustal evolution, with the oldest rocks on the continent preserved in the Manfred Complex, Narryer Terrane, with a magmatic crystallization age of c. 3730 Ma⁴. The denuded remains of even more ancient crust is retained as up to 4374 Ma detritus in the famous Narryer Terrane Jack Hills greenstone sequence⁵. Yet, outside the Narryer Terrane, elsewhere in the Yilgarn Craton, Nd and Hf isotope systematics have pointed towards a cryptic crustal substrate of Eoarchean to Paleoarchean age⁶. Specifically, very old > 4000 Ma whole rock Nd and zircon Hf model ages are known from samples of the northeastern part of the Archean Youanmi Terrane⁷. Additionally, detrital zircon grains from quartzite units of the Archean Southern Cross Domain in the central Yilgarn Craton have zircon ages ranging from c. 4350 Ma to c. 3130 Ma⁸ and rare >3100 Ma inherited zircon exists in some Youanmi Terrane granites and felsic volcanics⁹. Together these rather sparse data point towards ancient components, throughout the Yilgarn Craton, with temporal affinity to Narryer Terrane crust, the potential ancestral nucleus of the craton.

The South West Terrane defines the southwestern corner of the Yilgarn Craton and comprises granitic rocks, metasedimentary rocks, migmatite, and mafic to felsic gneisses^10,11. The granitic rocks yield magmatic crystallization ages of 2704–2607 Ma, whereas metamorphic overprinting highlights the effect of the Proterozoic c. 1095–990 Ma Pinjarra Orogeny and 780–515 Ma Leeuwin Orogeny along the western margin^12,13. Mafic rocks in the South West Terrane are relatively poorly dated, in part due to a lack of suitable geochronometers, and intense metamorphic overprinting¹⁴. Nevertheless, on a cratonic scale numerous dyke swarms are known to widely intrude the ancient cratonic basement, including the voluminous 2408–2401 Ma Widgiemooltha large igneous province^15,16 and c. 1210 Ma Marnda Moorn large igneous province related suites^17,18,19. Other dyke swarms that have been identified in the craton include; c. 2615 Ma Yandinilling Dolerite²⁰, c. 1888 Ma Boonadgin Dolerite^21,22, c. 1390 Ma Biberkine Dolerite²³, c. 1075 Ma Warakurna large igneous province²⁴, and c. 735 Ma Nindibillup Dolerite²⁵. Despite some of these suites having known expressions only within the central and northern part of the craton, the NE-trending Yandinilling Dolerite, the E-trending Widgiemooltha Dolerite, the WNW-trending Boonadgin Dolerite, the NNW-trending Biberkine Dolerite and the NW-trending (c. 1210 Ma) Boyagin Dolerite crop out in the South West Terrane.

The South West Terrane forms the southwestern corner of the Archean Yilgarn Craton (Fig. 1). It is bounded to the south by the Paleo to Mesoproterozoic Albany–Fraser Orogen, to the west by the Mesoproterozoic Pinjarra Orogen and overlying Permian to recent Perth Basin and to the northeast by the Archean Youanmi Terrane. The South West Terrane has been recently redefined as exposing relatively young granitic rocks with 2704–2607 Ma magmatic crystallization ages compared to the neighbouring 3018–2600 Ma Youanmi Terrane¹⁰. Relatively undeformed biotite-monzogranite form the majority of the outcrops within the terrane and are comparatively well-dated. Granitic gneisses and migmatites are also locally voluminous, but their ages are poorly known, leaving the possibility that older basement components are exposed in parts of the South West Terrane14. Whole-rock Sm–Nd isotopes from granites in the South West Terrane indicate two-stage depleted mantle model ages of 3430–2880 Ma²⁶, implying some Paleoarchean basement/inheritance. A suite of relatively young (2619–2607 Ma) granites are exposed towards the southwestern margin of the South West Terrane^14,27.

Fig. 1: Geological map of the southwest Yilgarn Craton, Western Australia.

Lithological divisions of the South West Terrane, overlying the 1:500,000-scale state map. Colours denote lithological units, where pinks are granitoids, greens are mafic intrusive rocks, and browns are sedimentary units. Inset depicts the terrane and domain structure of the craton. Red rectangle over the South West Terrane denotes detailed geology map provided as Supplementary Fig. A2.

Supracrustal rocks of the South West Terrane, with the exception of the Saddleback greenstone belt, are dominated by siliciclastic lithologies of largely unknown true depositional age due to a lack of datable volcanic horizons¹⁴. Psammitic and pelitic rocks collected from the Toodyay and Bridgetown areas show maximum depositional ages of c. 3200, 2670, and 2600 Ma¹⁴. These rocks commonly contain Meso- to Paleoarchean detrital zircons, with only a single Eoarchean detrital zircon dated at 3676 ± 12 Ma¹⁴. Unradiogenic Lu–Hf data measured from detrital zircon grains from modern beaches of southwestern Australia also suggest the presence of isotopically coherent Hadean-Eoarchean crustal vestiges associated with the southwestern border of the Yilgarn Craton²⁸.

NW-striking shear zones, possibly originating during the late Archean and reactivating during the Proterozoic, dissect the southwest corner of the South West Terrane10. These structures are truncated by north-striking faults and shear zones of the proto-Darling Fault. These proto-Darling Fault structures affect c. 1210 Ma dolerite dykes and are likely related to the 1095–990 Ma Pinjarra Orogeny and the 780–515 Ma Leeuwin Orogeny²⁹. A time space diagram of the region is provided as Supplementary Fig. A1.

The Archean pressure and temperature conditions of the South West Terrane are mostly unknown due to the general lack of suitable metamorphic assemblages. Nonetheless, greenschist- and amphibolite- to granulite-facies conditions have been inferred for some exposed gneisses and migmatite¹². Along the Darling Fault, amphibolite facies pressure-temperature conditions overprinted Archean mineral assemblages with metamorphic zircon and monazite growth at 1840, 1190, 1145, 1040, and 700 Ma14. Biotite Rb–Sr data from the Yilgarn Craton define a strong E-W trend in cooling ages, from 2480 Ma in the central Yilgarn Craton to younger than 500 Ma at the western margin of the craton close to the Darling Fault^30,31. These ages have been interpreted to reflect reworking or slow cooling in the central Yilgarn Craton after cratonisation, with the western margin also cooling following Gondwana assembly during the Ediacaran–Cambrian³². Near the dyke sample reported here (SW-1), the peak pressure–temperature estimate from pseudosection modelling is 5.5 kbar and 633 °C, best constrained at 707 ± 5 Ma based on metamorphic zircon and 667 ± 25 Ma by metamorphic monazite¹⁴.

Here we present the results of U–Pb geochronology on an amphibolite dyke from the South West Terrane (Supplementary Fig. A2) whose U-bearing accessory mineral cargo appears to track much of the Proterozoic and Mesozoic geological history of this margin. Importantly, the zircon inclusion cargo within titanite implies an inherited component of 3440 Ma age transported within the dyke. We complement these findings with detrital zircon geochronology from a sample of the Swan-Avon river system. This river system represents the largest fluvial system in the region, draining over 120,000 km2 of the South West and Youanmi terranes, with a palaeo-Swan River inferred to have been flowing in broadly the same position for at least 60 Ma³³. These detrital zircon results also support the presence of a Paleoarchean crustal component well to the south of the Narryer Terrane, or the widespread mobilisation of ancient detritus of this age.

Kirkland, C.L., Dröllner, M., Quentin de Gromard, R. et al.
Cryptic geological histories accessed through entombed and matrix geochronometers in dykes. Commun Earth Environ 5, 311 (2024). https://doi.org/10.1038/s43247-024-01469-6

Copyright: © 2024 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Of course creationists frauds can always lie about the dating methods and hope their target dupes are too ignorant to see through them, or too afraid to check, but what they can't do it change the fact that Earth is 4.5 billion years old so 99.99767% of its history happened before they want their cult to believe the Universe was magicked up out of nothing.

The fact that whoever wrote the Bible got that so badly wrong should be a reason for rational people to wonder how much else they got wrong, and how on earth can rational people believe it was written by the creator of everything, who appears to have been as ignorant and ill-informed as a parochial Bronze Age Canaanite pastoralist or a Christian fundamentalist from the American Bible Belt.

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