Pittsburgh, PA, August 3-8, 1998
Copyright 1998 by Creation Science Fellowship, Inc.
Pittsburgh, PA USA - All Rights Reserved
July 8, 9, 10, 11, 13, 14, 23, 28, 29, 30
August 15 (?), 18
September 16, 18, 26
1. Ejecta from March 1928 eruption [11,46]
2. Lava from February 1949 eruption [11, 46, 90]
3. Lava from June 30, 1954 flow [11, 27, 90]
4. 1954 lava (VU 29250) 
5. 1954 lava (VU 29250) [15, 69]
6. Average of four lava flows from 1954 eruptions [46, 70]
7. Average of five blocks and bombs from January and March 1974 eruptions [46, 70]
8. Lapilli from February 19, 1975 eruption 
|Table 1. Whole-rock, major-element oxide analyses of recent lava flows at Mt Ngauruhoe, New Zealand, as reported in the literature.|
|*Total Fe as Fe2O3||1. February 11, 1949 flow, samples A and B
2. June 4, 1954 flow, samples A and B
3. June 30, 1954 flow, samples A, B and C
4. July 14, 1954 flow, samples A and B
5. February 19, 1975 flow, samples A and B
|Table 2. Whole-rock, major-element oxide analyses of five recent lava flows at Mt Ngauruhoe, New Zealand (Analyst: AMDEL, Adelaide; April 1996).|
g* in groundmass
1. Ngauruhoe VU 29250 , a 1954 flow.
2. Olivine-bearing low-Si andesite, June 30, 1954 Ngauruhoe flow .
|Table 3. Modal analyses of two recent lava flows at Mt Ngauruhoe, New Zealand, as reported in the literature.|
l =the decay constant of the parent isotope
Dt=the number of daughter atoms in the rock presently
Do=the number of daughter atoms initially in the rock
Pt=the number of parent atoms presently in the rock
5.543 x 10-10=the current estimate for the decay constant of 40K
0.1048=the estimated fraction of 40K decays producing 40Ar
40Ar*/40K=the calculated mole ratio of radiogenic 40Ar to 40K in the sample
|Hualalai basalt, Hawaii (AD1800-1801)||1.6 - 0.16 Ma
1.41 -0.08 Ma
|Mt Etna basalt, Sicily (122BC)||0.25 -0.08 Ma|
|Mt Etna basalt, Sicily (AD1792)||0.35 - 0.14 Ma|
|Mt Lassen plagioclase, California (AD1915)||0.11 - 0.03 Ma|
|Sunset Crater basalt, Arizona (AD1064�1065)||0.27 - 0.09 Ma
0.25 - 0.15 Ma
|Akka Water Fall flow, Hawaii (Pleistocene)||32.3 - 7.2 Ma |
|Kilauea Iki basalt, Hawaii (AD1959)||8.5 - 6.8 Ma |
|Mt Stromboli, Italy, volcanic bomb (Sept. 23, 1963)||2.4 - 2 Ma |
|Mt Etna basalt, Sicily (May 1964)||0.7 - 0.01 Ma |
|Medicine Lake Highlands obsidian, Glass Mountains, California (<500 years old)||12.6 - 4.5 Ma |
|Hualalai basalt, Hawaii (AD1800�1801)||22.8 - 16.5 Ma |
|Rangitoto basalt, Auckland, NZ (<800 yrs old)||0.15 - 0.47 Ma |
|Alkali basalt plug, Benue, Nigeria (<30 Ma)||95 Ma |
|Olivine basalt, Nathan Hills, Victoria Land, Antarctica (<0.3 Ma)||18.0 - 0.7 Ma |
|Anorthoclase in volcanic bomb, Mt Erebus, Antarctica (1984)||0.64 - 0.03 Ma |
|Kilauea basalt, Hawaii (<200 yrs old)||21 - 8 Ma |
|Kilauea basalt, Hawaii (<1,000 yrs old)||42.9 - 4.2 Ma 
30.3 - 3.3 Ma 
|East Pacific Rise basalt (<1 Ma)||690 - 7 Ma |
|Seamount basalt, near East Pacific Rise (<2.5 Ma)||580 - 10 Ma 
700 - 150 Ma 
|East Pacific Rise basalt (<0.6 Ma)||24.2 - 1.0 Ma |
Dalrymple  suggested three possible explanations that might account for the excess 36Ar: (1) incorporation of "primitive argon", (2) production of 36Ar by the radioactive decay of 36Cl, or (3) fractionation of atmospheric argon by diffusion. He rejected the possibility of significant 36Ar formation in situ from nuclear reactions [option (2)] because the Cl content of basalts and the production rate of 36Cl by cosmic-ray neutrons both are too low to account for any significant amount of 36Ar. Instead, Dalrymple seemed to favor option (3), that when atmospheric argon diffused back into lavas as they cooled, 36Ar diffused in preferentially. However, he also recognized the weakness of this argument -- it is difficult to explain why some lavas are enriched in 36Ar while others are not (as at Mt Ngauruhoe also). To be consistent, if fractionation of atmospheric argon occurred during diffusion, then this would mean that even supposedly "zero age" lavas actually have an apparent age, and that most lavas do not degas upon eruption. In fact, depending on how strong the fractionation of 36Ar was during diffusion, it could even be that all lavas do not completely degas.
This only leaves Dalrymple's option (1), that the lavas with the anomalously high 36Ar come from areas of the mantle (and perhaps also the crust) which have primordial argon that has not been diluted with radiogenic 40Ar, and have not completely degassed. However, this means that there is no reason to assume that lavas whose argon matches that in the atmosphere have degassed either, because they may have simply started with argon which matches atmospheric argon. Nevertheless, Dalrymple is convinced that "much of the volatile juvenile content may still be present in volcanic rocks quenched on the ocean floor" . Indeed, Dalrymple has specifically defined excess 40Ar* as 40Ar that is not attributed to atmospheric argon or in situ radioactive decay of 40K . Krummenacher  is more cautious, attributing anomalous 40Ar/36Ar ratios and excess 40Ar* to the "mass fractionation effect on argon of atmospheric isotopic composition" trapped in the lavas, as well as to the presence of "magmatic" argon different in isotopic composition.
The Role of Xenoliths
Is the excess 40Ar* simply "magmatic" argon, that is, argon that collects in the magma and then is inherited by the lavas from it? Funkhouser and Naughton  found that the excess 40Ar* in the 1800?1801 Hualalai flow, Hawaii, resided in fluid and gaseous inclusions in olivine, plagioclase and pyroxene in ultramafic xenoliths in the basalt. The quantities of excess 40Ar* were sufficient to yield K-Ar model "ages" from 2.6 Ma to 2960 Ma. However, Dalrymple  subsequently only used the presence of the ultramafic xenoliths and their excess 40Ar* contained in inclusions to explain partly the excess 40Ar* and anomalous K-Ar model "ages" he obtained from the same 1800?1801 Hualalai flow, suggesting instead that the large single inclusions are not directly responsible for the excess argon in the flows and that the 40Ar* is distributed more uniformly throughout the rocks. Nevertheless, those K-Ar and Ar-Ar geochronologists who are concerned about the excess 40Ar* in their samples undermining their "dating" are careful to check for xenoliths, and xenocrysts. Esser et al.  did so and discounted xenocrystic contamination.
Xenoliths are present in the Ngauruhoe andesite flows (Table 3), but they are minor and less significant as the location of the excess 40Ar* residing in these flows than the plagioclase and pyroxene phenocrysts, and the much larger glomerocrysts of plagioclase, pyroxene, or plagioclase and pyroxene that predominate. The latter are probably the early-formed phenocrysts that accumulated together in the magma within its chamber prior to eruption of the lava flows. Nevertheless, any excess 40Ar* they might contain had to have been supplied to the magma from its source. The xenoliths that are in the andesite flows have been described by Steiner  as gneissic, and are therefore of crustal origin, presumably from the basement rocks through which the magma passed on its way to eruption.
Noble Gases from the Mantle
With the advent of the necessary technology, the isotopic concentrations and ratios of noble gases (including argon) in rock and mineral samples are now obtainable. Honda et al.  have reported such analyses on submarine basalt glass samples from Loihi Seamount and Kilauea, Hawaii, and concluded that helium and neon isotopic ratios in particular, being uniquely different from atmospheric isotopic ratios, are indicative of the mantle source area of the plume responsible for the Hawaiian volcanism rather than from atmopsheric contamination of the magma . The 40Ar/36Ar ratios are consistent with excess 40Ar* having also come with the magma from the mantle. A subsequent study , in which a larger suite of basalt glass samples, and also samples of olivine phenocrysts, from the same and additional Hawaiian volcanoes were analysed, concluded that the isotopic systematics indicate that the helium and neon have been derived from the mantle and have not been preferentially affected by secondary processes. Consequently, the excess 40Ar* also in these samples would have been also carried from the upper mantle source area of these basalts by the magma plume responsible for the volcanism. Moreira et al.  have suggested, based on new experimental data from single vesicles in mid-ocean ridge basalt samples dredged from the North Atlantic, that the excess 40Ar* in the upper mantle may be almost double previous estimates  (that is, almost 150 times more than the atmospheric content relative to 36Ar), and represents a primordial mantle component not yet outgassed. Burnard et al.  obtained similar results on the same samples, but maintained that because some of the 36Ar is probably surface-adsorbed atmospheric argon, the upper mantle content of excess 40Ar* could be even ten times higher.
Similar results  have been obtained from ultramafic mantle xenoliths in basalts from the Kerguelen Archipelago in the southern Indian Ocean, and the considerable excess 40Ar* measured concluded to be a part of the mantle source signature of this hotspot volcanism. However, it has not only been the suboceanic mantle that has thus been sampled for its excess 40Ar* via such magma plumes. Matsumoto et al.  have reported high 40Ar/36Ar ratios in spinel-lherzolites from five eruption centers in the youthful (<7 Ma) Newer Volcanics of southeastern Australia. These anhydrous lherzolites have compositions representative of the upper lithospheric mantle, and the significant excess 40Ar* in them indicates the presence of a subcontinental mantle reservoir with a very high 40Ar/36Ar ratio, and thus substantial excess 40Ar*, similar to that found in mid-ocean ridge and plume/hotspot basalts. Another example is the Cardenas Basalt and associated diabase (Middle Proterozoic) of eastern Grand Canyon, regarded as part of the pervasive mafic mid-continental magmatism of the southwestern United States and thus also sourced from the subcontinental mantle. Austin and Snelling  have found that the 40Ar/36Ar?40K/36Ar isochrons for 14 and six samples of these rocks respectively yield initial 40Ar/36Ar ratios of 787 ? 118 and 453 ? 42, indicative of some initial excess 40Ar*.
Sampling the Mantle with Diamonds and Their Inclusions
Another means of "sampling" the mantle is the study of diamonds and their micro-inclusions. It is now firmly established that diamonds are thermodynamically stable in the pressure-temperature regime in the mantle at depths greater than 150 km, and their origin is believed to extend back to the Archean and the early crust of the Earth [55, 56]. Diamonds are formed in a number of processes associated with two rock types, ecologite and peridotite, xenoliths of which are also brought up into the upper crust with diamonds from the upper mantle below continental Precambrian shields (cratons) by kimberlite and lamproite "pipe" eruptions [44, 45, 56]. Even though the host kimberlite or lamproite may be relatively young (even in conventional terms), many diamonds date back to the Archean and thus the early history of the Earth [56, 85]. To account for all this evidence, it is postulated that the formation of most diamonds was closely associated with subduction of the Archean oceanic crust into the mantle [55, 56], the required carbon, which was originally thought to be primordial carbon already in the mantle, now believed to derive from sedimentary marine carbonates and biogenic carbon from bacteria/algae in the sediments subducted with the oceanic crust [24, 56, 57].
The noble gas contents of diamonds are consistent with their ancient and mantle origin, high helium isotopic ratios (290 times the atmospheric ratio) being regarded as primordial and rivalling those measured for the Sun today [44, 73]. Of significance here is the postulation that He, Ar, K, Pb, Th and U are added to the convecting upper mantle circulation, and the proportions and isotopic compositions are strongly determined by entrainment from the lower mantle (below 670 km) [45, 50]. This is reflected in those Ar isotopic measurements that have been made on diamonds and their micro-inclusions.
Rather than focus on attempting to date only diamond micro-inclusions as others had done, Zashu et al.  carefully selected 10 Zaire diamonds and examined them for purity before undertaking K-Ar dating analyses of the diamonds themselves. However, at the outset they noted that there had been almost no direct radiometric dating of diamonds except for conventional K-Ar dating, and the results had been questionable due to the possible presence of excess 40Ar*. To avoid this problem, they used the K-Ar isochron dating method. Their experimental data showed good linear correlations, but these isochrons yielded an age of 6.0 ? 0.3 Ga, which of course was unacceptable because these diamonds would be older than the Earth itself. Mistakes in the experimental procedure were easily discounted, so they were forced to conclude that excess 40Ar* was responsible, and that it needed to be in a fluid state to ensure the homogenization necessary to give such a constant 40Ar/K ratio. Alternately, they speculated that the diamonds might differ in K isotopic composition from common potassium, but this was discounted in a follow-up study  in which it was found that 40K was present in these diamonds in normal abundance. Because 40Ar/39Ar analyses yielded the same unacceptable "age", it was concluded that the excess 40Ar* was not generated in situ, but was an inherited or "trapped" component from the mantle reservoir when and where the diamonds formed.
These Zaire diamonds are not the only ones which have yielded excess 40Ar*. Phillips et al.  used a laser-probe to 40Ar/39Ar date eclogitic clinopyroxene inclusions in diamonds from the Premier kimberlite, South Africa, and found moderate 40Ar/36Ar ratios indicative of much less excess 40Ar* than in the Zaire diamonds. The "age" of these eclogitic diamonds was thus determined to be 1.198 ? 0.014 Ga, much younger than the 3.3 Ga peridotitic diamonds at Kimberley and Finsch , also in South Africa, so Phillips et al.  interpreted the moderate excess 40Ar* as characteristic of mantle conditions prevailing at the time and in the region of Premier eclogitic diamond formation.
Zashu et al.  postulated that the excess 40Ar* in the Zaire diamonds needed to be in a fluid state. Though Navon et al.  did not analyse for argon when they investigated fluids in micro-inclusions in diamonds from Zaire and Botswana, they found a high content of volatiles and incompatible elements in the uniform average composition of the micro-inclusions, with the amounts of water and CO2 (in carbonates) almost an order of magnitude higher than the volatile contents of kimberlites and lamproites (host rocks to diamonds). At 1?3 wt%, the chlorine levels were also much higher than those of kimberlites (<0.1%), although the bulk composition of the micro-inclusions, including the high K2O content (up to 29.7 wt%), resembled that of such potassic magmas. They concluded that these micro-inclusions represent the volatile-rich (~40% volatiles) fluid or melt from the upper mantle in which the diamonds grew, and that because of the high volatile content in this hydrous mantle fluid, high levels of rare gases may also be expected and explain the high 40Ar/K ratios (the excess 40Ar*) and anomalous "ages".
As a result of continued investigation of the Zaire cubic diamonds, which produced 40Ar/39Ar age spectra yielding a ~5.7 Ga isochron, Ozima et al.  discovered that just as there was an excellent correlation between their potassium contents and 40Ar/36Ar ratios, there is also a correlation between their chlorine contents and 40Ar. They concluded from their data "that the 40Ar is an excess component which has no age significance, and that the 40Ar and its associated potassium are contained in sub-micrometer inclusions of mantle-derived fluid." Turner et al.  also used the 40Ar/39Ar technique through correlations with K, Cl and 36Ar to unscramble the mixtures of radiogenic and parentless (excess) Ar components in fluid inclusions in "coated" Zaire diamonds and in olivine from an East African mantle xenolith. Their results proved conclusively that 40Ar is present in a widespread chlorine-rich component, which implies the existence of H2O/CO2-rich phases with 40Ar/Cl ratios that are "remarkably uniform over large distances", with enrichments of these two incompatible elements by almost four orders of magnitude relative to bulk upper-mantle values. Clearly, excess 40Ar* is abundant in the mantle and can be easily transported up into the crust.
Crustal Excess 40Ar*
Is there only evidence for excess 40Ar* in the mantle, gleaned from rocks (basalts and ultramafic xenoliths) and minerals (olivine, pyroxene, plagioclase and diamonds) that were formed in, or ascended from, the mantle? Patterson et al.  envisage noble gases from the mantle (and the atmosphere) migrating and circulating through the crust, so there should be evidence of excess 40Ar* in crustal rocks and minerals. In fact, noble gases in CO2-rich natural gas wells support such migration and circulation ?that is, the isotopic signatures clearly indicate a mantle origin for the noble gases, including amounts of excess 40Ar* in some CO2-rich natural gas wells exceeding those in the mantle-derived mid-ocean ridge basalts [6, 10, 66, 88, 89]. Staudacher  also notes that the quantities of excess 40Ar* in the continental crust can be as much as five times that found in such mantle-derived mid-ocean ridge basalts , strongly suggesting that excess 40Ar* in crustal rocks and their constituent minerals could well be the norm rather than the exception, thus making all K-Ar (and Ar-Ar) dating questionable.
It has now been established that some diamonds can form in the crust ? during high-grade metamorphism [22, 87] and via shock metamorphism during meteorite or asteroid impact . The pressures and temperatures of high-grade metamorphism had been regarded as insufficient to produce diamonds, but the key ingredient was found to be volatile N2-CO2-rich fluids. Noble gas data on these diamonds are not yet available, due to their size and rarity, but such data have been definitive in establishing the crustal origin of carbonado diamonds . Nevertheless, they still contain excess 40Ar*.
Dalrymple , referring to metamorphism and anatexis of rocks in the crust, commented, "If the rock is heated or melted at some later time, then some or all the 40Ar may escape and the K-Ar clock is partially or totally reset". In other words, 40Ar* escapes to migrate in the crust where it may then be incorporated in other minerals as excess 40Ar*, just as 40Ar* degassing from the mantle does. Thus, for example, excess 40Ar* has been recorded in many minerals (some of which contain no 40K) in crustal rocks, such as quartz, plagioclase, pyroxene, hornblende, biotite, olivine, beryl, cordierite, tourmaline, albite and spodumene [33, 61] ? in pegmatites, metamorphic rocks, and lavas. And it is not just K-Ar dating analyses that detect excess 40Ar*, as Lanphere and Dalrymple  used the 40Ar/39Ar method to confirm the presence of excess 40Ar* in feldspars and pyroxenes. Indeed, in a recent study , 128 Ar isotopic analyses were obtained from ten profiles across biotite grains in amphibolite-granulite facies metamorphic rocks, and apparent 40Ar/39Ar "ages" within individual grains ranged from 161 to 514 Ma. The investigators concluded that these observations cannot be solely due to radiogenic build-up of 40Ar*, but must be the result of incorporation by diffusion of excess 40Ar* from an external source, namely, 40Ar* from the mantle and other crustal rocks and minerals. Indeed, Harrison and McDougall  were able to calculate a well-defined law for 40Ar diffusion from hornblende in a gabbro due to heating. They also found that the excess 40Ar* which had developed locally in the intergranular regions of the host gabbro reached partial pressures in some places of at least 10-2 atm.
This crustal migration of 40Ar* is known to cause grave problems in attempted regional geochronology studies. In the Middle Proterozoic Musgrave Block of northern South Australia, Webb  found a wide scatter of K-Ar mineral ages ranging from 343 Ma to 4493 Ma due to inherited (or excess) 40Ar*, so that no meaningful interpretation could be drawn from the rocks (granulite, gneiss, pseudotrachylite, migmatite, granite and diabase). Of the diabase dikes which gave anomalous ages, he concluded that "The basic magmas probably formed in or passed through zones containing a high partial pressure of 40Ar*, permitting inclusion of some of the gas in the crystallizing minerals." Likewise, when Baski and Wilson  attempted to argon date Proterozoic granulite-facies rocks in the Fraser Range (Western Australia) and Strangways Range (central Australia), they found that garnet, sapphirine and quartz in those rocks contained excess 40Ar* that rendered their argon dating useless because of "ages" higher than expected. They also concluded that the excess 40Ar* was probably incorporated at the time of formation of the minerals, and their calculations suggested a partial pressure of ~0.1 atm Ar in the Proterozoic lower crust of Australia, which extends over half the continent.
In a detailed 40Ar/39Ar dating study of high-grade metamorphic rocks in the Broken Hill region of New South Wales (Australia), Harrison and McDougall  found evidence of widely distributed excess 40Ar*. The minerals most affected were plagioclase and hornblende, with step heating 40Ar/39Ar "age" spectra yielding results of up to 9.588 Ga. Such unacceptable "ages" were produced by excess40Ar* release, usually at temperatures of 350?650?C and/or 930?1380?C, suggesting the excess 40Ar* is held in sites within the respective mineral lattices with different heating requirements for its release. There are three principal trapping sites for Ar in solids ? structural holes, edge dislocations and lattice vacancies. (Argon is also known to be held sometimes in some minerals in fluid inclusions.) Clearly, this study shows that at crustal temperatures, which are less than 930?C, some excess 40Ar* will always be retained in those trapping sites in minerals where it is obviously "held" more tightly, thus rendering K-Ar and 40Ar/39Ar dating questionable. Harrison and McDougall  were only able to produce a viable interpretation of the data because they made assumptions about the expected age of the rocks and of a presumed subsequent heating event (based on Pb-Pb and Rb-Sr dating), the latter being the time when they conjecture that accumulated 40Ar* was released from minerals causing a significant regional Ar partial pressure of ~3x10-4 atm to develop.
Mantle-Crust Domains and Excess 40Ar*
Harte and Hawkesworth  have identified domains within the mantle and crust and described the interaction between them, all of which is relevant to the migration and circulation of argon (and thus excess 40Ar*) from the lower mantle to the crust and to lavas extruded on the Earth?s surface. The six domains are physically distinct units which show wide differences in average physical and chemical properties, as well as apparent age, structure, and tectonic behavior. They are the lower mantle (below 670 km), upper mantle, continental mantle lithosphere, oceanic mantle lithosphere, continental crust and oceanic crust, and each is a distinct geochemical reservoir. Each domain may provide material for magmatic rocks, and particular geochemical features of magmas may be associated with particular domains. Thus the convecting upper mantle which comes to the surface at mid-ocean ridges may be identified as the source of most geochemical features of mid-ocean ridge basalts, including their excess 40Ar* content. Similarly, the convecting lower mantle is regarded as the primordial or bulk Earth geochemical reservoir, which may also contribute excess 40Ar* to mid-ocean ridge basalts, but is more important for its contribution to ocean island basalts (e.g. Hawaii) and other plume-related basalts (continental alkali basalts and continental flood basalts). However, considerable complexity may be added to the deeper mantle geochemical structure as a result of localized accumulation of subducted oceanic lithosphere.
Porcelli and Wasserburg  have proposed a steady-state upper mantle model for mass transfer of rare gases, including argon. The rare gases in the upper mantle are derived from mixing of rare gases from the lower mantle, subducted rare gases, and radiogenic nuclides produced in situ. Porcelli and Wasserburg claim that all of the 40Ar in the closed-system lower mantle has been produced by 40K decay in the lower mantle, but this claim is based on the assumption of a 4.5 Ga Earth. In any case, they contradict themselves, because they also state [82, p. 4924], "The lower mantle is assumed to have evolved isotopically approximately as a closed system with the in situ decay of 129I, 244Pu, 238U, 232Th, and 40K adding to the complement of initial rare gases." In other words, they admit that some of the 40Ar must be primordial and not dervied from radioactive 40K. They then go on to claim that in the upper mantle, 40K decay further increases the radiogenic 40Ar from the lower mantle by a factor of ~3, but again this presupposes a 4.5 Ga Earth and doesn?t allow for primordial 40Ar that could well be also in the upper mantle if it?s admitted to be in the lower mantle.
In the case of the continental and oceanic lithospheric domains, the lack of convective stirring means that different geological processes and events may implant in each domain a variety of geochemically distinct materials which will remain isolated from one another. Therefore, these domains do not have a single set of geochemical characteristics; thus identification of geochemically defined "sources" with particular physically defined crust-mantle domains is complex, and the geochemical definition of particular reservoirs cannot be regarded as simply definition of major physical entities. Nevertheless, excess 40Ar* will be added to these domains by the passage of basaltic magma plumes from the upper mantle to the Earth?s surface.
Furthermore, the processes of oceanic lithosphere formation from the convecting upper mantle in association with mid-ocean ridge activity mean that its isotopic characteristics everywhere will be largely similar to those of the convecting upper mantle and mid-ocean ridge basalts, including the addition of excess 40Ar*. The corollary to this is that the oceanic crust is formed as part of these same processes. However, the oceanic crust generally has a thin veneer of sediments over it, and thick wedges of sediments adjacent to the domains of continental crust, whereas sections of oceanic crust are hydrothermally altered. The compositions of these components of the oceanic crust may, therefore, include a considerable contribution from continental detritus and ocean water, so that this oceanic crustal material may give rise to a distinct geochemical reservoir, the fate of which during subduction back into the upper mantle becomes critically important if it contributes to island arc volcanics, plume-related intra-place magmas and mantle-derived xenoliths.
The complexity of continental crustal material is well known through direct observation, and the mantle lithosphere attached to it may be expected to show a similar complexity. Nevertheless, it is evident that excess 40Ar* also resides in the continental mantle lithosphere, as indicated by xenoliths . Likewise, there is evidence of excess 40Ar* in crustal magmatic rocks (e.g., gabbros , pegmatites ), migrating through metamorphic terrains [5, 48, 96], and in natural gas in sedimentary reservoirs .
Mt Ngauruhoe in its Tectonic Framework
The presence, therefore, of excess 40Ar* in the recent andesite flows at Mt Ngauruhoe is to be expected. The Taupo Volcanic Zone is a volcanic arc and marginal basin of the Taupo-Hikurangi arc-trench system (see Figure 1 again), which is a southward extension of the Tonga-Kermadec arc into the continental crustal environment of New Zealand?s North Island . Geophysical investigations indicate that the Pacific Plate is being obliquely subducted beneath the Australian Plate on which most of New Zealand?s North Island sits, and that the volcanoes of the Taupo Volcanic Zone, including Ngauruhoe in the Tongariro Volcanic Center, are about 80 km directly above the subducting Pacific Plate, a zone of earthquakes revealing where the movement is taking place . Friction along the plane of contact is believed to cause melting to produce pockets of magma, which then feed via conduits to the volcanoes above. Thus the recent andesite flows at Mt Ngauruhoe are calc-alkaline island arc volcanics.
The tectonic and geochemical framework of the Ngauruhoe andesite flows within the mantle-crust domains of Harte and Hawkesworth  is that of subducting oceanic crust (derived from the convecting upper mantle), carrying with it the wedge of continental sedimentary detritus which has accumulated at the continental margin and in the adjacent trench to the east of the coastline. Attached beneath the subducting oceanic crust is its associated oceanic mantle lithosphere, and together they are being thrust downwards into the upper mantle. Above the subducting plate are the continental crust and continental mantle lithosphere of the overriding plate, the continental crust being at the contact plane at shallow depths near the trench, and then the attached continental mantle lithosphere beneath at a depth of about 35 km . Thus the geochemical reservoir from which the Ngauruhoe andesite magma has been drawn is potentially a mixture of melted oceanic crust, continental sedimentary detritus and continental crust, and possibly continental mantle lithosphere, or even upper mantle.
Genesis of the Mt Ngauruhoe Andesite Magma and its Excess 40Ar*
One of the easier investigations of the petrogenesis of these volcanic rocks of the Taupo Volcanic Zone was that of Stipp , and Ewart and Stipp . They analysed samples that had been systematically collected, including not only the lavas and the pyroclastics, but also the Permian to Jurassic interbedded greywackes, siltstones and shales (the potential crustal source rocks) which are spatially related to, and underlie, the volcanics. Of primary interest were Sr, Rb and K contents, and 87Sr/86Sr and 87Rb/86Sr ratios. Three possibilities for the origin of the calc-alkaline andesite magma were under investigation ? fractional crystallization of a basalt magma under oxidizing conditions; some form of hybridization between basaltic and acidic magmas, possibly followed by fractional crystallization; and derivation of a primary andesite magma from the upper mantle. Ewart and Stipp  regarded their Sr isotopic data as more consistent with the production of the andesites by partial assimilation of sedimentary material by basaltic magma (derived from the upper mantle), the adjacent greywackes, siltstones and shales being the most likely sedimentary material, and the unassimilated gneissic xenoliths probably representing the basement rocks to those sediments. However, they admitted that the data did not exclude the possibility of a primary andesitic magma derived directly from the upper mantle, provided that some assimilation of crustal material modified it prior to eruption.
Subsequent investigations by Cole  favored the alternate petrogenetic model of a primary andesitic magma. He suggested that the subducting oceanic crust assimilated the greywacke-siltstone-shale and overlying sediments east of the Taupo Volcanic Zone to produce amphibolite, which subsequently broke down to produce phlogopite eclogite below 90 km. This in turn partially melted at 150?200 km, and the resultant magma fractionated in the upper mantle or lower crust to produce andesite. However, based on rare-earth element geochemistry, Cole et al.  modified that petrogenetic model, suggesting that while the andesite magma genesis was probably associated in the upper mantle with the downgoing slab and some crustal contamination occurred, the andesite does not appear to have had an eclogite parent. This would then suggest that the melting associated with the subducting slab to generate the andesite magma occurred at a depth of less than 90 km.
Graham and Hackett  agreed with this conclusion, demonstrating from geophysical evidence that the top of the subducting slab is at a depth of about 80 km below Ngauruhoe, and that the crust there is probably less than 20 km thick. Thus the upper mantle wedge between would consist only of plagioclase-peridotite and spinel-peridotite. At 80 km depth the hydrated amphibolite assemblage of the upper portion of the subducting slab of oceanic crust and oceanic mantle lithosphere would have started to dehydrate, thus liberating water and possibly other volatile constituents into the overlying upper mantle wedge, significantly lowering its melting point. Graham and Hackett  then showed that the geochemical evidence requires the andesite magma for the Ngauruhoe lava flows to have been generated from an original low-alumina basalt magma produced in the upper mantle wedge by anatexis of the asthenosphere (uppermost mantle) and/or subcontinental mantle lithosphere probably catalysed by hydrous, metasomatic fluids from the subducting slab.
Some specific geochemical enrichment then appears to have occurred as a result of this mantle metasomatism and continental crustal contamination during ascent and storage of the magma. Graham and Hackett  used least squares geochemical modelling to show how the andesite magma could be generated from such a parent basalt magma by a process of combined assimilation of crustal material (addition of 6 per cent assimilant) and fractional crystallization (30 per cent removal of crystals). Furthermore, the presence of xenoliths in the Ngauruhoe andesite flows, particularly the vitrified meta-greywacke and gneissic xenoliths, indicate conclusively that the assimilant was most likely a partial melt of gneiss, originally the adjacent greywacke-siltstone-shale sediments [38, 39].
These processes responsible for the generation of the andesite magma did not diminish the excess 40Ar* content of the resultant flows. Though the amount of excess 40Ar* is not high when compared with that found in mid-ocean ridge basalts, it is nonetheless significant that the excess 40Ar* was still present in the lavas upon eruption and cooling. The evidence indicates that the parent basaltic magma was generated in the upper mantle where the excess 40Ar* in the geochemical reservoir is now known to be upwards of 150 times more than the atmospheric content, relative to 36Ar. The subsequent crustal contamination and fractional crystallization to form the andesite magma during ascent, and the degassing of the magma during eruption and lava flow and cooling, did not remove all the excess 40Ar*, a small portion of which was left to be trapped in the congealed lava and its constituent minerals.
This model for the generation of the andesite magma in the post-Flood world is, of course, based on the plate tectonics model for global tectonics through Earth history. Even though the postulated plate movements today are extremely slow, and thus extrapolated back over millions of years by uniformitarians, a catastrophic model for plate tectonics in the context of the Flood is entirely compatible with both Scripture and the scientific data . Plate movements are regarded as occurring catastrophically during the Flood and then rapidly slowing down to today?s rates in the post-Flood era.
The fact that there is even some excess 40Ar* in these recent andesite flows, and that it appears to have ultimately come from the upper mantle geochemical reservoir, where it is regarded as leftover primordial argon not yet fully expelled by the process of outgassing that is supposed to have occurred since the initial formation of the Earth, has very significant implications.
First, this is clearly consistent with a young Earth, where the very short time-scale since the creation of the Earth has been insufficient for all the primordial argon to be released yet from the Earth?s deep interior. Furthermore, it would also seem that even the year-long global catastrophic Flood, when large-scale convection and turdecer occurred in the mantle , was insufficient to expel all the deep Earth?s primordial argon.
Second, this primordial argon is, in part, "excess" 40Ar not generated by radioactive decay of 40K, which has then been circulated up into crustal rocks where it may continue migrating and building up to partial pressure status regionally. Because the evidence clearly points to this being the case, then when samples of crustal rocks are analysed for K-Ar "dating" the investigators can never really be sure that whatever 40Ar* is in the samples is from in situ radioactive decay of 40K since the formation of the rocks, or whether some or all of it is from the "excess 40Ar*" geochemical reservoirs in the lower and upper mantles. This could even be the case when the K-Ar analyses yield "dates" compatible with other radioisotopic "dating" systems and/or with fossil "dating" based on evolutionary assumptions. And there would be no way of knowing because the 40Ar* from radioactive decay of 40K cannot be distinguished analytically from primordial 40Ar not from radioactive decay, except of course by external assumptions about the ages of the samples.
Therefore, these considerations call into question all K-Ar "dating", whether "model ages" or "isochron ages", and all 40Ar/39Ar "dating", as well as "fossil dating" that has been calibrated against K-Ar "dates". Although seemingly insignificant in themselves, the anomalous K-Ar "model ages" for these recent andesite flows at Mt Ngauruhoe, New Zealand, lead to deeper questions. Why is there excess40Ar* in these rocks? From where did it come? Answers to these questions in turn point to significant implications that totally undermine such radioactive "dating" and that are instead compatible with a young Earth.
Further research is very definitely warranted. The most pressing need is to attempt to quantify how much primordial 40Ar there is today in the upper mantle. Also, how much has circulated into crustal rocks, how much is in natural gas reservoirs, and how much might have escaped into the atmosphere during 6,000?7,000 years, including accelerated rates during the Flood. It might then be possible to quantify how much primordial 40Ar there was in the mantle at the time of the Earth?s creation. From these calculations and associated modelling exercises there might develop quantifiable evidence for the Earth?s youthfulness.
Additionally, further research is needed to quantify how much "excess 40Ar*" is in all the crustal rocks and minerals that have been, and are, subject to K-Ar and 40Ar/39Ar "dating". This would include what are regarded as mantle xenoliths and xenocrysts (e.g. diamonds). It is helpful to show on the one hand that such "dating" is questionable, but on the other hand there are still many "dates" that are concordant, that is, they agree with other uniformitarian dating systems and schemes. So ultimately we need to explain why that happens when other "dates" are discordant and anomalous. There may, in fact, be some pattern or systematic way in which "excess40Ar" has been trapped in rocks and occluded in minerals at different levels (depths and relative ages) in the geological record. If so, then K-Ar and 40Ar/39Ar "dating" would irrevocably be discredited.
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