Page 87 of 157 FirstFirst ... 377786878897137 ... LastLast
Results 3,011 to 3,045 of 5477

Thread: Scientific knowledge

  1. #3011
    Join Date
    Oct 1999
    Location
    St. Paul, MN, USA
    Posts
    49,969

    Default Re: Scientific knowledge

    And one might ask why an allegedly benevolent deity would go kill everybody in the first place, but expecting myths to make sense is probably fruitless. Yahweh had a pretty short fuse, you believe the stores.
    "For a successful technology, reality must take precedence over public relations,
    for nature cannot be fooled."

    Richard Feynman

  2. #3012
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by WX View Post
    I had a go at opal mining on an uncles claim, it’s hard work. Finding opal is a bit look looking for a pin on football field from under the ground. The synthetic looks quite good.
    this may have been the basis of the flood myth.
    https://en.m.wikipedia.org/wiki/Blac...uge_hypothesis
    I think that is quite likely. Of course the displaced people could just walk away from that one, no Arks were harmed in making their escape. The other stories that may have been absorbed into the Old Testament are the Gilgamesh myth and this one
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  3. #3013
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,442

    Default Re: Scientific knowledge

    I did wonder if the flooding of the Mediterranean might have been origin but at 5.5 million years it would be a bit of a long bow.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  4. #3014
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by WX View Post
    I did wonder if the flooding of the Mediterranean might have been origin but at 5.5 million years it would be a bit of a long bow.
    There is also this: https://www.theguardian.com/science/...ws.archaeology
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  5. #3015
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,442

    Default Re: Scientific knowledge

    Quote Originally Posted by Peerie Maa View Post
    And 9,000 years ago there was this.
    https://www.theguardian.com/science/...tralian-island
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  6. #3016
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by WX View Post
    And 9,000 years ago there was this.
    https://www.theguardian.com/science/...tralian-island
    “Around 8,000 years ago, it would have been on the coast,” McDonald told Guardian Australia. “This is the time that the islands were starting to be cut off and it’s a time when people were starting to rearrange themselves.”
    The sea level on Australia’s north-west coast rose 130 metres after the end of the ice age, at a rate of about a metre every five to 10 years. “In people’s lifetimes they would have seen loss of territory and would have had to renegotiate – a bit like Miami these days,” McDonald said.
    Made me think of Dogger Land
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  7. #3017
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    some people here rekon that I tell lies .....)

    humbly,

    frank
    Quote Originally Posted by Peerie Maa View Post
    Got a quote for that? Link to a post?
    Quote Originally Posted by Frank! View Post
    why would you believe anything I give you then?
    Quote Originally Posted by Peerie Maa View Post
    Try me.
    Let us put this to bed shall we.
    Frank you did not provide a link or quote a post because you know that nobody called you out for telling lies. Yes?
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  8. #3018
    Join Date
    Jan 2008
    Location
    Wow-Ming
    Posts
    17,524

    Default Re: Scientific knowledge

    CREATIONLAND. A Super-Lative, Educational Experience, such as you have never witnessed!














    We're merely mammals. Let's misbehave! —Cole Porter

  9. #3019
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    Quote Originally Posted by Peerie Maa View Post
    Let us put this to bed shall we.
    Frank you did not provide a link or quote a post because you know that nobody called you out for telling lies. Yes?
    Nick - I have sent you a PM.

  10. #3020
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    Nick - I have sent you a PM.
    Not arrived yet, it's a long way from Aus.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  11. #3021
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    I understand that it is not usual - but occasionally , using different Radiometric daiting on the same rock does give different ages.

    One study using Potassium ,rubidium ,uranium and neodymium decay sequences gave significantly (by up to a factor of 3x !) different results on one rock tested.

    It was found that discordant dates were measured also in three overlying layers.

    further analysis revealed that, though the measurements were inconsistent there was a consistent pattern - in fact several!

    - for any one method, a lower layer always gave an older age than a higher one

    - for any one layer, the resultant ages were always in the same order.

    because of the consistent patterns, a random or other error was ruled out - it was accepted that the ages accurately reflected the method used.

    One possibility to account for all this was that a "period" of accelerated radioactive decay was experienced though this explanation would not be accepted by many.

    Further research was called for.


    Now I have posted this in response to those who (like myself) prefer results in the real world of reality....

    I can dig that rock is tested in laboratories with dedicated, trained staff, and conducted according to defined protocols. (and indeed the results, by exhibiting those particular , consistent patterns, bears that out)

    I look forward to a good explanation.

  12. #3022
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    I understand that it is not usual - but occasionally , using different Radiometric daiting on the same rock does give different ages.

    One study using Potassium ,rubidium ,uranium and neodymium decay sequences gave significantly (by up to a factor of 3x !) different results on one rock tested.

    It was found that discordant dates were measured also in three overlying layers.

    further analysis revealed that, though the measurements were inconsistent there was a consistent pattern - in fact several!

    - for any one method, a lower layer always gave an older age than a higher one

    - for any one layer, the resultant ages were always in the same order.

    because of the consistent patterns, a random or other error was ruled out - it was accepted that the ages accurately reflected the method used.

    One possibility to account for all this was that a "period" of accelerated radioactive decay was experienced though this explanation would not be accepted by many.

    Further research was called for.


    Now I have posted this in response to those who (like myself) prefer results in the real world of reality....

    I can dig that rock is tested in laboratories with dedicated, trained staff, and conducted according to defined protocols. (and indeed the results, by exhibiting those particular , consistent patterns, bears that out)

    I look forward to a good explanation.
    A link to the paper would be good, so that we can read it first hand. How else can we be expected to explain it in a vacuum?
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  13. #3023
    Join Date
    Jan 2005
    Location
    Deepest Darkest Wales
    Posts
    19,751

    Default Re: Scientific knowledge

    Cite?
    Creationists aren't mad - they're possessed of demons.

  14. #3024
    Join Date
    Mar 2006
    Location
    Victoria, BC
    Posts
    10,652

    Default Re: Scientific knowledge

    "And those who were seen dancing were thought to be insane by those who could not hear the music." Nietzsche


  15. #3025
    Join Date
    Jan 2008
    Location
    Wow-Ming
    Posts
    17,524

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post

    - for any one method, a lower layer always gave an older age than a higher one

    - for any one layer, the resultant ages were always in the same order.
    This is wrong. Depositional stratigraphy can be altered by crustal forces, producing zones of folding where the layers are inverted with respect to their original sequence. Here's a simple diagram.




    I live in an area where crustal forces have oriented the stratigraphy pretty near vertical, so the relative position, up or down, does not translate to earlier or later dates.

    Perhaps you should take a course on the subject. Interesting stuff.
    We're merely mammals. Let's misbehave! —Cole Porter

  16. #3026
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by Peerie Maa View Post
    A link to the paper would be good, so that we can read it first hand. How else can we be expected to explain it in a vacuum?
    Frank, is that one of Snellings papers?
    http://www.asa3.org/ASA/education/origins/rate-ri.htm
    Thought about post #2967 yet?
    The problem with the Young Earth Creationist view, based on the genealogy of the bible:
    Table 1: Table of Patriarchs

    From Stevens, 2003

    Key
    F: Age of fatherhood L: Length of Life
    B: Birth date (Anno mundi) D: Date of Death (Anno mundi)

    Septuagint Samaritan Masoretic
    Age Year Age Year Age Year
    Patriarch F L B D F L B D F L B D
    Adam 230 930 0 930 130 930 0 930 130 930 0 930
    Seth 205 912 230 1142 105 912 130 1042 105 912 130 1042
    Enosh 190 905 435 1340 90 905 235 1140 90 905 235 1140
    Cainan 170 910 625 1535 70 910 325 1235 70 910 325 1235
    Mahalalel 165 895 795 1690 65 895 395 1290 65 895 395 1290
    Jared 162 962 960 1922 62 847 460 1307 162 962 460 1422
    Enoch 165 365 1122 1487 65 365 522 887 65 365 622 987
    Methuselah 187 969 1287 2256 67 720 587 1307 187 969 687 1656
    Lamech 188 753 1474 2227 53 653 654 1307 182 777 874 1651
    Noah 502 950 1662 2612 502 950 707 1657 502 950 1056 2006
    Flood 2262 1307 1656
    Shem 100 600 2164 2764 100 600 1209 1809 100 600 1558 2158
    Arphachshad 135 615 2264 2879 135 438 1309 1747 35 438 1658 2096
    Cainan 130 460 2399 2859
    Shelah 130 460 2529 2989 130 433 1444 1877 30 433 1693 2126
    Eber 134 504 2659 3163 134 404 1574 1978 34 464 1723 2187
    Peleg 130 339 2793 3132 130 239 1708 1947 30 239 1757 1996
    Reu 132 339 2923 3262 132 239 1838 2077 32 239 1787 2026
    Serug 130 330 3055 3385 130 230 1970 2200 30 230 1819 2049
    Nahor 79 208 3185 3393 79 148 2100 2248 29 148 1849 1997
    Terah 70 205 3264 3469 70 145 2179 2393 70 205 1878 2083
    Abraham 100 175 3334 3509 100 175 2249 2424 100 175 1948 2123
    Isaac 60 180 3434 3614 60 180 2349 2529 60 180 2048 2228
    Jacob 147 3494 3641 147 2409 2556 147 2108 2255




    Is that our bodies stop replacing old cells as we age, so we wear out and die at a maximum age of about 125years. The YEC's argue that germs and diseases had not developed back then to kill us which illustrates an ignorance of genetics. It is our genes that kill us even if we could avoid bugs and viruses. What happens to telomeres as we age?



    • Each time a cell divides, 25-200 bases are lost from the ends of the telomeres on each chromosome.
    • Two main factors contribute to telomere shortening during cell division?:
      • The “end replication problem” during DNA replication: Accounts for the loss of about 20 base pairs? per cell division.
      • Oxidative stress: Accounts for the loss of between 50-100 base pairs per cell division. The amount of oxidative stress in the body is thought to be affected by lifestyle factors such as diet, smoking and stress.

    • When the telomere becomes too short, the chromosome reaches a ‘critical length’ and can no longer be replicated.
    • This ’critical length’ triggers the cell to die by a process called apoptosis?, also known as programmed cell death.




    https://www.yourgenome.org/facts/what-is-a-telomere
    So most of that column, "Age at Fatherhood" cannot be correct. Thus the entire edifice falls.
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  17. #3027
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,442

    Default Re: Scientific knowledge

    I've come across a fundamentalist creationist on Facebook that Makes Frank seem quite reasonable.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  18. #3028
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    One for the biologists.
    Scientists think they have the answer to a puzzle that baffled even Charles Darwin: How flowers evolved and spread to become the dominant plants on Earth.
    Flowering plants, or angiosperms, make up about 90% of all living plant species, including most food crops.
    In the distant past, they outpaced plants such as conifers and ferns, which predate them, but how they did this has has been a mystery.
    New research suggests it is down to genome size - and small is better.
    "It really comes down to a question of cell size and how you can build a small cell and still retain all the attributes that are necessary for life," says Kevin Simonin from San Francisco State University in California, US.

    'Abominable mystery'
    Hundreds of millions of years ago, the Earth was dominated by ferns and conifers. Then, about 150 million years ago, the first flowering plants appeared on the scene.
    They quickly spread to all parts of the world, changing the landscape from muted green to a riot of vibrant colour.
    The reasons behind the incredible success and diversity of flowering plants have been debated for centuries.
    Charles Darwin himself called it an "abominable mystery", fearing this apparent sudden leap might challenge his theory of evolution.
    http://www.bbc.co.uk/news/science-environment-42656306
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  19. #3029
    Join Date
    Oct 1999
    Location
    St. Paul, MN, USA
    Posts
    49,969

    Default Re: Scientific knowledge

    One study using Potassium ,rubidium ,uranium and neodymium decay sequences gave significantly (by up to a factor of 3x !) different results on one rock tested.
    Sure. Our methods are imperfect, and sometimes give conflicting results. But you are positing a factor of 1,000,000x.
    Last edited by Keith Wilson; 01-14-2018 at 06:41 PM.
    "For a successful technology, reality must take precedence over public relations,
    for nature cannot be fooled."

    Richard Feynman

  20. #3030
    Join Date
    Jan 2005
    Location
    Deepest Darkest Wales
    Posts
    19,751

    Default Re: Scientific knowledge

    The classic Potassium/Argon resets on melt (hardly a surprise Argon's a gas) - been known for decades and is commonly accounted for - note the lack of a citation.
    Creationists aren't mad - they're possessed of demons.

  21. #3031
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    for those enquiring minds ....

    re. discordant dates from different radiometric dating sequences - on the same rock sample:

    T. Oberthür, D. W. Davis, T. G. Blenkinsop, and A. Höhndorf, “Precise U-Pb Mineral Ages, Rb-Sr and Sm-Nd Systematics of the Great Dyke, Zimbabwe—Constraints on Late Archean Events in the Zimbabwe Craton and Limpopo Belt,” Precambrian Research 113:293–305, 2002;

    S. B. Mukasa, A. H. Wilson, and R. W. Carlson, “A Multielement Geochronologic Study of the Great Dyke, Zimbabwe: Significance of the Robust and Reset Ages,” Earth and Planetary Science Letters 164:353–369, 1998;

    J. Zhao, and M. T. McCulloch, “Sm-Nd Mineral Isochron Ages of Late Proterozoic Dyke Swarms in Australia: Evidence for Two Distinctive Events of Mafic Magmatism and Crustal Extension,” Chemical Geology 109:341–354, 1993.

    enjoy!

    frank

  22. #3032
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    and note:

    - reset on melt doesn't apply cos it is the one nad same sample for all the methods ......

    - systematic conflicting results means there is a problem ....

    -

  23. #3033
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    Quote Originally Posted by Nanoose View Post
    thanks Nanoose - I enjoyed the presentations

    I think it well illustrates what I have been trying to say all along, accepting the possibility of a creator liberates one to follow the science.

    Rejecting a priori the possibility of a creator means one can only accept evidence that agrees with that assumption
    - evolution is the only theory that doesn't need a creator
    - evolution is only possible over unimaginably long time scales
    - if there is not enough time, we are back to the need for a creator

    hence creationists can follow the science - since the creator might have taken just as long (or short) a time as he (or she / it) pleases. One thus is free to consider any and all the evidences without concern that one's own personal belief (or non-belief) system could be shot down in flames.

    when that revelation hit me (at the time I was neither atheist, nor hardcore believer - sort of agnostic) it was so liberating to realise that I could follow my investigations into the reality of everything without having to worry about the implications ..... they could take care of themselves when I had done the practical stuff.

    I seem to have ended up here presenting the creationists stuff - but I think that is because everyone here is evolutionist and they seem to have little grasp of the other point of view. (to my great surprise - I did expect a balanced mix of evolutionists and others - and I have been very shocked by the vehemence of some ppl posting here)

    if it had been the other way around and it had been a hotbed of creationism, I think my contrarian nature would have had me digging out evolutionist stuff ......

    anyway

    cheers,

    frank

  24. #3034
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    Quote Originally Posted by Chip-skiff View Post
    This is wrong. Depositional stratigraphy can be altered by crustal forces, producing zones of folding where the layers are inverted with respect to their original sequence. Here's a simple diagram.




    I live in an area where crustal forces have oriented the stratigraphy pretty near vertical, so the relative position, up or down, does not translate to earlier or later dates.

    Perhaps you should take a course on the subject. Interesting stuff.
    I should have specified "layers as originally laid down"

    in which case the fundamental principle of Geology holds true - "younger on top, older below"

  25. #3035
    Join Date
    Mar 2010
    Location
    central cal
    Posts
    14,760

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    thanks Nanoose - I enjoyed the presentations

    I think it well illustrates what I have been trying to say all along, accepting the possibility of a creator liberates one to follow the science.

    Rejecting a priori the possibility of a creator means one can only accept evidence that agrees with that assumption
    - evolution is the only theory that doesn't need a creator
    - evolution is only possible over unimaginably long time scales
    - if there is not enough time, we are back to the need for a creator

    hence creationists can follow the science - since the creator might have taken just as long (or short) a time as he (or she / it) pleases. One thus is free to consider any and all the evidences without concern that one's own personal belief (or non-belief) system could be shot down in flames.

    when that revelation hit me (at the time I was neither atheist, nor hardcore believer - sort of agnostic) it was so liberating to realise that I could follow my investigations into the reality of everything without having to worry about the implications ..... they could take care of themselves when I had done the practical stuff.

    I seem to have ended up here presenting the creationists stuff - but I think that is because everyone here is evolutionist and they seem to have little grasp of the other point of view. (to my great surprise - I did expect a balanced mix of evolutionists and others - and I have been very shocked by the vehemence of some ppl posting here)

    if it had been the other way around and it had been a hotbed of creationism, I think my contrarian nature would have had me digging out evolutionist stuff ......

    anyway

    cheers,

    frank
    If you care to challenge my understanding of religious creation stories, I am open to it. I’m familiar with all the majors, most of their antecedents, and most (if not all) of the American religions, and their stories.

    Evolution is neither someing to believe in, nor opposed to any “creator” ideology, except by those who choose to pretend science is attempting to destroy God, when in reality, as God is all things, science is a way to understanding God.
    After all, to a Christian, God is the alpha and omega, eh? Everything that was is and will be, yeah?

    But, as in all things, we cling to our clans and credos at the expense of all others outside our field, and drive wedges and wedges and wedges.

    Peace,
    Mayor Of Babel, A Confused And Scared Ape

  26. #3036
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    for those enquiring minds ....

    re. discordant dates from different radiometric dating sequences - on the same rock sample:

    T. Oberthür, D. W. Davis, T. G. Blenkinsop, and A. Höhndorf, “Precise U-Pb Mineral Ages, Rb-Sr and Sm-Nd Systematics of the Great Dyke, Zimbabwe—Constraints on Late Archean Events in the Zimbabwe Craton and Limpopo Belt,” Precambrian Research 113:293–305, 2002;

    S. B. Mukasa, A. H. Wilson, and R. W. Carlson, “A Multielement Geochronologic Study of the Great Dyke, Zimbabwe: Significance of the Robust and Reset Ages,” Earth and Planetary Science Letters 164:353–369, 1998;

    J. Zhao, and M. T. McCulloch, “Sm-Nd Mineral Isochron Ages of Late Proterozoic Dyke Swarms in Australia: Evidence for Two Distinctive Events of Mafic Magmatism and Crustal Extension,” Chemical Geology 109:341–354, 1993.

    enjoy!

    frank
    None of those three papers seem to say what you think they say.
    6. Summary and conclusions
    (1) U–Pb geochronology precisely constrains the crystallization age of the Great Dyke to 2575.490.7 Ma.
    (2) Different apparent ages for the Great Dyke deduced from Rb–Sr to Sm –Nd isochrons are probably due to inhomogeneous initial isotopic ratios, which resulted from mixing of mantle magma with variable amounts of a crustal com- ponent added in situ during intrusion.
    (3) While the greenstone sequences of the Zim- babwe craton were formed prior to :2.65 Ga, the ages of late Archean Chilimanzi and Razi suite granitoids bracket the intrusion age of the Great Dyke. It follows that the Chilimanzi and Razi suites of granitoids form at least two sub-suites each, being pre- and post-Great Dyke in age.
    (4) In the NMZ of the Limpopo belt, thrusting, metamorphism and granitoid emplacement are all confined to the time interval 2669–2517 Ma, a time period, which overlaps with the age of intrusion of the Great Dyke. The minimum age of thrusting in the western part of the NMZ is the same age as the Great Dyke, whereas younger granitoids are deformed by thrusting in the east. Thrusting, magmatism and cratonization may therefore be diachronous from west to east.
    (5) The overlap in the ages of the intrusion of the Great Dyke and late Archean events in the Zimbabwe craton shows that Archean crust was cratonized shortly after large-scale melting and granite intrusion.
    Precise U-Pb mineral ages, Rb-Sr and Sm-Nd systematics for the Great Dyke, Zimbabwe - Constraints on late Archean events in the Zimbabwe craton and Limpopo belt (PDF Download Available). Available from: https://www.researchgate.net/publica...d_Limpopo_belt [accessed Jan 14 2018].
    Abstract

    New Sm-Nd, U-Pb, and Pb-Pb age determinations indicate that the Great Dyke of Zimbabwe, an elongate intrusion of mafic and ultramafic rocks some 550 km long and between 3 and 10 km wide, is over 100 Ma older than previously believed based on Rb-Sr ages. The intrusion was emplaced as a series of subchambers with similar stratigraphy, comprising a lower ultramafic sequence with cyclic layering of dunite or harzburgite grading upwards into bronzitite, the top sections of which include Pt-enriched sulfide zones, and an upper mafic sequence of pyroxenites capped by olivine gabbro and gabbronorite. The Sm-Nd method has yielded a combined mineral/whole-rock isochron of 2586 ± 16 Ma and ε(Nd)(t) of +1.1 for samples from the Darwendale, Sebakwe, and Wedza Subchambers as well as the satellite East Dyke. This isochron age is in excellent agreement with the U-Pb age for three concordant rutile fractions extracted from a feldspathic pyroxenite of the Selukwe Subchamber with an error-weighted mean at 2587 ± 8 Ma. Two zircon fractions from the same feldspathic pyroxenite sample as the rutile are discordant, and although not well constrained, suggest Pb loss from the zircons at ca. 830 Ma. This may be related to the onset of the widespread and diachronous Pan-African tectonothermal event in southern Africa. Whole-rock samples and clinopyroxene and plagioclase separates from a Darwendale Subchamber drill core yielded a 207Pb/204Pb vs. 206Pb/204Pb isochron age of 2596 ± 14 Ma, which is in agreement with the Sm-Nd isochron and the rutile U-Pb crystallization age. This new age information shows that emplacement of the Great Dyke and its satellite dikes closely followed the amalgamation of the Kaapvaal and Zimbabwe Cratons, and was contemporaneous with emplacement of the youngest of the trondhjemite-tonalite-granodiorite granitoid suite in the Zimbabwe Craton. Assuming that amalgamation of the Kaapvaal and Zimbabwe Cratons was largely by NNW-directed convergence, it follows that the source of the Great Dyke was asthenospheric mantle hydrated and enriched in incompatible elements by subduction processes. Isochrons of 206Pb/204Pb vs. 238U/204Pb and 207Pb/204Pb vs. 235U/204Pb yield ages with large errors, but well constrained initial Pb ratios (206Pb/204Pb = 14.15 ± 0.30 and 207Pb/204Pb = 15.04 ± 0.06). Assuming a two-stage model for common lead evolution, this result yields a μ value of 9.5. Along with the calculated initial Sr and Nd isotopic compositions, these data are consistent with derivation of the Great Dyke magmas by large volume melting of a mantle that has been hydrated and enriched by subduction. While a small amount of crustal contamination of magma derived from depleted mantle could produce the composition of the Great Dyke, the uniformity of initial ratios between subchambers supports the notion of enrichment in incompatible elements being an intrinsic characteristic of the mantle source.

    SmNd mineral isochron ages of Late Proterozoic dyke swarms in Australia: evidence for two distinctive events of mafic magmatism and crustal extension

    Author links open overlay panelJian-xinZhaoMalcolm T.McCulloch



    https://doi.org/10.1016/0009-2541(93)90079-XGet rights and content
    Abstract

    Two distinctive events of widespread dyke intrusion have been identified in central-southern Australia. Crystallization ages of the dykes were determined using SmNd mineral isochrons obtained by splitting clinopyroxene and plagioclase into different magnetic and density fractions, respectively. The Stuart Dyke Swarm in the southern Arunta Inlier and the Kulgera Dyke Swarm in the eastern Musgrave Inlier define essentially identical crystallization ages of 1076 ± 33 and 1090 ± 32 Ma, respectively, marking the first episode of post-orogenic mafic magmatism in the region. Two samples from the Gairdner Dyke Swarm in the Stuart Shelf yield SmNd mineral isochron ages of 867 ± 47 and 802 ± 35 Ma, respectively, whilst two samples from the Amata suite in the central Musgrave Inlier, 790 ± 40 and 797 ± 49 Ma. These four ages represent the second episode of mafic magmatism in central-southern Australia. These ages allow new constraints to be placed on the timing of large-scale crustal extension and formation of intracratic depositional basins in the region.
    Initial ϵNd-values of − 7.8 to − 6.6 for the Stuart dykes and + 0.7 for the Kulgera dykes suggest they were derived from different mantle sources with the Stuart dykes being produced from strongly enriched sources. In contrast, positive and relatively uniform initial ϵNd-values of + 2.5 to + 4.1 for the younger Amata Suite and Gairdner dykes indicate that they were derived from relatively depleted and homogeneous mantle sources.
    The 1076 ± 33-Ma SmNd age of the Stuart Dyke Swarm is significantly older than its Rb-Sr mineral isochron age of 897 ± 9 Ma previously reported, suggesting mobility of Rb and/or Sr and partial resetting of Rb-Sr isotopic systematics.
    This study demonstrates that reliable and relatively precise SmNd ages can be obtained for Precambrian dykes, despite the limited number of mineral phases available in the dykes.



    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  27. #3037
    Join Date
    Sep 2007
    Location
    Bass Harbor, ME
    Posts
    2,734

    Default Re: Scientific knowledge

    There are many reasons that radiometric dates done by different methods on a single sample would disagree. It has to do the the details of the specific minerals in the sample, how the dates were done and the thermal and alteration history of the sample. That the dating results differ is actually useful because it allows the reconstruction of the thermal history of the sample. This is rather basic isotope geochemistry that needs to be understood before interpreting radiometric dates.

  28. #3038
    Join Date
    Oct 2008
    Location
    Walney, near Cumbria UK
    Posts
    41,009

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    thanks Nanoose - I enjoyed the presentations

    I think it well illustrates what I have been trying to say all along, accepting the possibility of a creator liberates one to follow the science.

    Rejecting a priori the possibility of a creator means one can only accept evidence that agrees with that assumption
    - evolution is the only theory that doesn't need a creator
    - evolution is only possible over unimaginably long time scales
    - if there is not enough time, we are back to the need for a creator

    hence creationists can follow the science - since the creator might have taken just as long (or short) a time as he (or she / it) pleases. One thus is free to consider any and all the evidences without concern that one's own personal belief (or non-belief) system could be shot down in flames.

    when that revelation hit me (at the time I was neither atheist, nor hardcore believer - sort of agnostic) it was so liberating to realise that I could follow my investigations into the reality of everything without having to worry about the implications ..... they could take care of themselves when I had done the practical stuff.

    I seem to have ended up here presenting the creationists stuff - but I think that is because everyone here is evolutionist and they seem to have little grasp of the other point of view. (to my great surprise - I did expect a balanced mix of evolutionists and others - and I have been very shocked by the vehemence of some ppl posting here)

    if it had been the other way around and it had been a hotbed of creationism, I think my contrarian nature would have had me digging out evolutionist stuff ......

    anyway

    cheers,

    frank
    Have you got your head round the fact that telomeres make a 6000 year age for the earth an erroneous proposition?
    Which means that we only have to worry about a 4.5billion year old earth, and that all of the non creationist science works.
    Last edited by Peerie Maa; 01-15-2018 at 04:21 AM. Reason: better grammar
    It really is quite difficult to build an ugly wooden boat.

    The power of the web: Anyone can post anything on the web
    The weakness of the web: Anyone can post anything on the web.

  29. #3039
    Join Date
    Jan 2008
    Location
    Wow-Ming
    Posts
    17,524

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    I should have specified "layers as originally laid down"

    in which case the fundamental principle of Geology holds true - "younger on top, older below"
    Never heard about igneous intrusions?

    You are a babe in woods.
    We're merely mammals. Let's misbehave! —Cole Porter

  30. #3040
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    Quote Originally Posted by Todd D View Post
    There are many reasons that radiometric dates done by different methods on a single sample would disagree. It has to do the the details of the specific minerals in the sample, how the dates were done and the thermal and alteration history of the sample. That the dating results differ is actually useful because it allows the reconstruction of the thermal history of the sample. This is rather basic isotope geochemistry that needs to be understood before interpreting radiometric dates.
    Hi Todd,

    So there is a problem ?

    Is there any way that a period of accelerated decay could account for the discordant dates as the article suggests?

    I appreciate that it verges on special pleading, but. ........

    Regards,

    Frank
    Last edited by Frank!; 01-14-2018 at 11:04 PM.

  31. #3041
    Join Date
    Sep 2007
    Location
    Bass Harbor, ME
    Posts
    2,734

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    Hi Todd,

    So there is a problem ?

    Is there any way that a period of accelerated decay could account for the discordant dates as the article suggests?

    I appreciate that it verges on special pleading, but. ........

    Regards,

    Frank
    No because "accelerated decay" doesn't exist.

  32. #3042
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,442

    Default Re: Scientific knowledge

    Quote Originally Posted by Frank! View Post
    thanks Nanoose - I enjoyed the presentations

    I think it well illustrates what I have been trying to say all along, accepting the possibility of a creator liberates one to follow the science.

    Rejecting a priori the possibility of a creator means one can only accept evidence that agrees with that assumption
    - evolution is the only theory that doesn't need a creator
    - evolution is only possible over unimaginably long time scales
    - if there is not enough time, we are back to the need for a creator

    hence creationists can follow the science - since the creator might have taken just as long (or short) a time as he (or she / it) pleases. One thus is free to consider any and all the evidences without concern that one's own personal belief (or non-belief) system could be shot down in flames.

    when that revelation hit me (at the time I was neither atheist, nor hardcore believer - sort of agnostic) it was so liberating to realise that I could follow my investigations into the reality of everything without having to worry about the implications ..... they could take care of themselves when I had done the practical stuff.

    I seem to have ended up here presenting the creationists stuff - but I think that is because everyone here is evolutionist and they seem to have little grasp of the other point of view. (to my great surprise - I did expect a balanced mix of evolutionists and others - and I have been very shocked by the vehemence of some ppl posting here)

    if it had been the other way around and it had been a hotbed of creationism, I think my contrarian nature would have had me digging out evolutionist stuff ......

    anyway

    cheers,

    frank
    Unimaginable time? Have you considered the unimaginable distances between even the closest stars to us?
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  33. #3043
    Join Date
    Feb 2002
    Location
    Uki, NSW, Australia
    Posts
    26,442

    Default Re: Scientific knowledge

    Given the great pyramids of Egypt are 4,500 years old and we can measure the amount of weathering that has taken place that time it would appear obvious that an age of 6,000 years for the earth is a physical impossibility.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  34. #3044
    Join Date
    Dec 2003
    Location
    Portland, Oregon
    Posts
    49,409

    Default Re: Scientific knowledge

    Why yes... it IS a very powerful tool. But only if you know how to use it.

    Just like my nifty hatchet can be used for the mundane (kindling), the creative (carving), or the destructive (mass carnage). Frank seems to yearn for the first two, but mostly manages the latter (at least in a logical sense).


    Last edited by David G; 01-15-2018 at 10:23 AM.
    David G
    Harbor Woodworks
    http://www.harborwoodworking.com/boat.html

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  35. #3045
    Join Date
    May 2012
    Posts
    1,444

    Default Re: Scientific knowledge

    Not feeling funny tonight.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •