Radiohalos in the Cooma Metamorphic Complex, New South Wales, Australia: The Mode and Rate of Regional Metamorphism

The Cooma metamorphic complex in southeastern Australia is a classical example of regional metamorphic zones centered on a granodiorite generated by partial melting at the highest metamorphic grade. Samples collected along a traverse from the low-grade biotite and then andalusite zone schists through the high-grade K-feldspar and migmatite zone gneisses into the central granodiorite contain increasing numbers of Po radiohalos with increasing metamorphic grade. The highest Po radiohalo numbers are in the high-grade zones and the granodiorite. These radiohalo patterns correlate with the Po radiohalos being generated by the hydrothermal fluids flowing out of the central granodiorite as it crystallized and cooled, their numbers diminishing as the hydrothermal fluid flow decreased outwards. This is further evidence consistent with the hydrothermal transport model for Po radiohalo formation. Furthermore, generation of the regional metamorphic complex only required 12–20 days, based on the catastrophic granite formation of the adjacent Murrumbidgee Batholith whose heat and hydrothermal fluids generated the regional metamorphic zones of the complex from the mineral constituents of the original fossiliferous sediment layers, then the central granodiorite as a consequence. This sequence of outcomes is consistent with creationist models for catastrophic granite formation and regional metamorphism driven by catastrophic plate tectonics during the year-long biblical Flood

Significance of Highly Discordant Radioisotope Dates for Precambrian Amphibolites in Grand Canyon, USA

The Brahma amphibolites of the Precambrian crystalline basement of Grand Canyon were originally erupted as basalt lavas and subsequently suffered high-grade regional metamorphism. Composed predominantly of hornblende with minor subordinate plagioclase, the collected samples showed no signs of post-metamorphic alteration. K-Ar radioisotope analyses yielded a wide range of model ages, even for adjacent samples from the same outcrop of the same original lava flow. No statistically viable K-Ar isochron age could be obtained because of so much scatter in the data, which is most likely due to 40Ar* mobility within these rocks. By contrast, the Rb-Sr, Sm-Nd, and Pb-Pb radioisotope systems yielded good, statistically consistent, isochron ages of 1240 ± 84 Ma, 1655 ± 40 Ma, and 1883 ± 53 Ma, respectively. These are obviously discordant with one another and with published ages, but there are no clear reasons to reject any of them as unreliable or invalid. One explanation for the discordance is that the decay rates of the parent radioisotopes were different relative to their presently measured rates at some time during the time interval since these rocks formed. We observe that the α-decaying U and Sm yield older ages than the β-decaying Rb, and the heavier atomic weight U yields a PbPb age older than the Sm-Nd age. This pattern in the discordances thus may provide clues into the physics responsible for time variations in the decay process. Obviously, if decay rates have not been constant, radioisotope decay methods do not yield valid absolute ages for rocks

The Relevance of Rb-Sr, Sm-Nd and Pb-Pb Isotope Systematics to Elucidation of the Genesis and History of Recent Andesite Flows at Mt. Ngauruhoe, New Zealand, and the Implication for Radioisotopic Dating

Mt Ngauruhoe in the Taupo Volcanic Zone of New Zealand erupted andesite lava flows in 1949 and 1954, and avalanche deposits in 1975. Rb-Sr, Sm-Nd and Pb-Pb radioisotopic analyses of samples of these andesites, as anticipated, did not yield any “age” information, although the Pb isotopic data are strongly linear. When compared with recent andesite flows from the related adjacent Ruapehu volcano, the Sr-Nd-Pb radioisotopic systems plotted on correlation diagrams provide information about the depleted mantle source for the parental basalt magmas and the source of the crustal contamination that produced the andesite lavas from them. The variations in both the depleted mantle Nd “model ages” and the Pb isotopes also suggest radioisotopic heterogeneity in the mantle wedge 80 km below the volcano where partial melting has occurred, contaminated by mixing with trench sediments scraped off the interface with the subducting slab. Thus the radioisotopic ratios in these recent Ngauruhoe andesite flows were inherited, and reflect the origin and history of the mantle and crustal sources from which the magma was generated. By implication, the radioisotopic ratios in ancient lavas throughout the geologic record are likely fundamental to their geochemistry, characteristic of their origin and history rather than necessarily providing valid conventional “ages”

Radiohalos as an Exploration Pathfinder for Granite-related Hydrothermal Ore Veins: A Case Study in the New England Batholith, Eastern Australia

It has been proposed that Po radiohalos were formed from Po derived by 238U decay in the radiocenters of nearby 238U radiohalos which was transported by hydrothermal fluids released from granite plutons as they cooled. Thus, since the same hydrothermal fluids have concentrated metals into economic ore veins in some granites, it has also been proposed Po radiohalos could potentially be used as an exploration pathfinder tool for discovering new ore veins associated with granites. This study in the New England Batholith, eastern Australia, found that Mole Granite samples proximal to known hydrothermal ore veins contained extremely high numbers of Po radiohalos, in contrast to a distant sample that contained almost 90% fewer Po radiohalos. However, in the Hillgrove Granite which also hosts hydrothermal ore veins, all samples contained moderate-high numbers of Po radiohalos similar to those in barren granite plutons elsewhere in the batholith. This is because the Hillgrove ore veins were not produced from the hydrothermal fluids expelled from that cooling pluton, but were precipitated from hydrothermal fluids as distant granitoid plutons cooled in a later magmatic event. Thus, the extremely high numbers of Po radiohalos in Mole Granite samples proximal to known ore veins successfully indicated their proximity to those ore veins. Therefore, Po radiohalos proved to be a reliable pathfinder for the hydrothermal ore veins. This strategy applied to the Stanthorpe Granite found two out of six samples with high to very high numbers Po radiohalos, potentially pinpointing areas for follow-up exploration for possible hydrothermal ore veins. Further detailed sampling work is recommended to develop this exploration tool. Nevertheless, since the same hydrothermal fluid flows responsible for the Po radiohalos were responsible for forming the ore veins, then the ore veins must have formed in the same very rapid timescale, within weeks, a timescale fully compatible with the biblical chronology of earth history

Radiohalos in the Shap Granite, Lake District, England: Evidence that Removes Objections to Flood Geology

The Shap Granite in the Lake District of northern England intruded the surrounding host rocks as a magma that released hydrothermal fluids as it crystallized and cooled. These hot fluids in turn produced an atypically wide contact metamorphic and metasomatic aureole around the intrusion. There is no evidence at the boundary for tectonic emplacement of a primordial cold granite body. This study documents an abundance of Po radiohalos in the Shap Granite. These Po radiohalos had to have been produced in the granite after the hydrothermal fluids released in the granite had assisted in the formation of the granite’s distinctive orthoclase feldspar megacrysts, and after the crystallized granite had subsequently cooled below the 150 °C annealing temperature of radiohalos. The abundance of Po radiohalos is consistent with the hydrothermal fluid transport model for Po radiohalo formation and with catastrophically rapid granite formation. These features imply that the Shap Granite formed in 6–10 days and its Po radiohalos within hours to days once the granite cooled below 150 °C. Hydraulic fracturing of the host rocks overlying the pluton facilitated rapid unroofing of the granite. Continued rapid erosion then deposited granite pebbles in the basal conglomerate of the overlying limestone. It is, therefore, conceivable that the Shap Granite formed, was unroofed, and the basal conglomerate with granite pebbles was deposited, all within 2–3 weeks during the early-middle part of the Flood year. The Po radiohalos and other evidence associated with this granite thus remove objections to Flood geology and any need to place the Flood/post-Flood boundary in the lower Carboniferous

U-TH-PB: An Example of False Isochrons

As with other isochron methods, the U-Pb isochron method has been questioned in the open literature, because often an excellent line of best fit between ratios obtained from a set of good cogenetic samples gives a resultant \u27isochron\u27 and yields a derived \u27age\u27 that has no distinct geological meaning. At Koongarra, Australia, U·Th·Pb Isotopic studias of uranium ore, host rocks and soils have produced an array of false \u27isochrons\u27 that yield \u27ages\u27 that are geologically meaningless. Even a claimed near·concordant U-Pb \u27age\u27 of 862Ma on one uraninite grain is identical to a false Pb-Pb isochron \u27age\u27, but neither can be connected to any geological event. Open system behaviour of the U-Th-Pb system is clearly the norm, as is the resultant mixing of radiogenic Pb with common or background Pb, even in soils in the surrounding region. Because no geologically meaningful results can be interpreted from the U-Th-Pb data at Koongarra (three uraninite grains even yield a 232Th/208Pb \u27age\u27 of OMa), serious questions must be asked about the validity of the fundamental/foundational basis of the U-Th-Pb \u27dating\u27 method. This makes the task of creationists building their model for the geological record much easier, since claims of U-Th-Pb radiometric \u27dating\u27 having \u27proven\u27 the claimed great antiquity of the earth, its strata and fossils can be safely side-stepped

Regional Metamorphism Within a Creationist Framework: What Garnet Compositions Reveal

The \u27classical\u27 model for regional metamorphic zones presupposes elevated temperatures and pressures due to deep burial and deformation/tectonic forces over large areas over millions of years - an apparent insurmountable hurdle for the creationist framework. One diagnostic metamorphic mineral is garnet, and variations in its composition have long been studied as an Indicator of metamorphic grade conditions. Such compositional variations that have been detected between and within grains in the same rock strata are usually explained in terms of cationic fractionation with changing temperature during specific continuous reactions involving elemental distribution patterns in the rock matrix around the crystallizing garnet. Garnet compositions are also said to correlate with their metamorphic grade. However, contrary evidence has been Ignored. Compositional patterns preserved in garnets have been shown to be a reflection of compositional zoning in the original precursor minerals and sediments. Compositional variations between and within garnet grains In schists that are typical metapelites at Koongarra in the Northern Territory, Australia, support this minority viewpoint. Both homogeneous and compositionally zoned garnets, even together in the same hand specimen, display a range of compositions that would normally reflect widely different metamorphic grade and temperature conditions during their supposed growth. Thus the majority viewpoint cannot explain the formation of these garnets. It has also been demonstrated that the solid·solid transformation from a sedimentary chlorite precursor to garnet needs only low to moderate temperatures, while compositional patterns only reflect original depositional features In sedimentary environments. Thus catastrophic sedimentation, deep burial and rapid deformatlon/tectonlcs with accompanying low to moderate temperatures and pressures during, for example, a global Flood and its aftermath have potential as a model for explaining the \u27classical\u27 zones of progressive regional metamorphism

Whole-rock K-Ar Model and Isochron, and Rd-Sr and Pb-Pb Isochron, Dating of the Somerset Dam Layered Mafic Intrusion, Australia

The Somerset Dam layered mafic intrusion in southeast Queensland, Australia, has been conventionally dated as Late Triassic by the apparently successful application of radioisotopic dating techniques. Mineralogical, geochemical and isotopic evidence indicates that all of this gabbro intrusion’s cyclic units were derived coevally from the same parental basaltic magma, with an initial homogeneous isotopic mixture ideal for yielding concordant isochron ages. However, newly obtained K-Ar, Rb-Sr, Sm-Nd and Pb-Pb radioisotopic data from 15 whole-rock samples (representing all gabbro macrolayers in four of the intrusion’s cyclic units) yield discordant isochron “ages”, although the excellent-fitting 15-point K-Ar isochron suggests the resultant 174±8 Ma “age” (Middle Jurassic) should be regarded as the revised conventional age of the layered intrusion. Nevertheless, it is concluded that these discordances between the radioisotope systems are likely due to changes in their decay rates in the past, with the longer halflife beta-emitter 87Rb being accelerated more and thus yielding an older “age”. Furthermore, the Sr, Nd and Pb isotopes indicate the parental basaltic magma was derived from a depleted mantle source, while the large spread of Nd TDM “ages” suggests accelerated radioisotopic decay rates during the partial melting and magma ascent. It is concluded that the Somerset Dam layered mafic intrusion has inherited the radioisotopic signature of its mantle source, and so the conventional radioisotopic dating techniques do not provide its true age

The Cause of Anomalous Potassium-Argon Ages for Recent Andesite Flows at Mt. Ngauruhoe, New Zealand, and the Implications for Potassium-Argon Dating

New Zealand\u27s newest and most active volcano, Mt Ngauruhoe in the Taupo Volcanic Zone, produced andesite flows in 1949 and 1954, and avalanche deposits in 1975. Potassium-argon dating of five of these flows and deposits yielded K-Ar model ages from \u3c0.27 Ma to 3.5 ± 0.2 Ma. Dates could not be reproduced, even from splits of the same samples from the same flow, the explanation being variations in excess \u27Ar* content. A survey of anomalous K-Ar dates indicates they are common, particularly in basalts, xenoliths and xenocrysts such as diamonds that are regarded as coming from the upper mantle. In fact, it is now well established that there are large quantities of excess \u27Ar* in the mantle, which in part represent primordial argon not produced by in situ radioactive decay of .40K and not yet outgassed. And there are mantle-crust domains between, and within, which argon circulates during global tectonic processes, magma genesis and mixing of crustal materials. This has significant implications for the validity of K-Ar and 40Ar/39Ar dating

Locating the Flood/post-Flood Boundary Using the Relative Dating of the Weathering of Ore Deposits

Erosion at the end of and after the Flood exposed the tops of primary ore deposits to subsequent weathering and the formation of supergene minerals. The 40Ar/39Ar and (U-Th)/He radioisotope methods applied to these supergene minerals provide the dates for when these minerals formed. But given the documented problems with the radioisotope methods, they can only provide at best relative dates. When the Flood waters retreated, the ground surface was dry, but extra time was needed to allow the water table to drop, soil to form and plants to grow before Noah stepped off the Ark, which marked the end of the Flood event. The weathering front then progressed downwards during the early post-Flood decades for supergene minerals to start forming. Residual post-Flood catastrophism may have involved mountains still rising and ore deposits still forming, such as the porphyry copper deposits associated with granite intrusions as the Andes continued to rise. Erosion exposed those later-formed ore deposits to subsequent weathering to produce supergene minerals well into the early post-Flood era. Thus, the relative ages of the supergene iron oxides, and potassium-bearing sulfates and manganese oxides produced span the whole Cenozoic. It is proposed that relative dates for the first formation of supergene minerals can possibly be used as a criterion for determining the placement of the Flood/post-Flood boundary at the K-Pg boundary with a relative age of 66 Ma. The few slightly earlier relative ages likely resulted from weathering that commenced before the Flood event ended, though deep weathering would have required decades. The spread of relative ages through the Cenozoic thus represents the progressive formation of supergene minerals as primary ore deposits emplaced during, and maybe after, the Flood were subsequently exposed to weathering by residual catastrophism. Continuing investigation of this criterion for placement of the Flood/post-Flood boundary seems warranted