Formation Hypotheses of White Mountain Magma Series

Formation Hypotheses of fresh upsurge Magma SeriesJulie Sophis macrocosmA grouping of fervid rocks, similar in chemical, texture, and minera lucid features which come from a common reference point magma and atomic number 18 within a similar magazine and space when intruded be considered a magma series (Lachance, 1978). The etiolate voltaic pile Magma Series, WMMS, is situated primarily in juvenile Hampshire with a few related plutons mapped in Maine and Vermont. This series received much of its recognition in 1956 and earlier (McHone and Butler, 1984). The gaberdine circle Magma Series has been placed as part of the revolutionary England-Quebec responsibleness, representing torrid activity which is considered to be of similar ages and similar compositions that stretches over an area of 300km by 400km through southern Quebec and new(a) England (McHone and Butler, 1984). This magmatism of the whole bloodless Mountain igneous province is characterized as A-type (Eby, 1999). In looking specific solelyy at the White Mountain Magma Series, two distinct condemnation frames of igneous activity are found, one senior and one younger.The older igneous activity, referred to as the older White Mountain Igneous state of matter (OWM), dates to 220-155 Ma (Eby and Kennedy, 2004). Alkali syenites, quartz syenites, metaluminous granite, peralkaline granite, peralkaline rhyolites, and two areas of identified silica-undersaturated rock hold in been identified (Eby and Kennedy, 2004). There is an absence of mafic igneous rocks and this older area consists of multiple ring dikes (Eby and Kennedy, 2004).The younger igneous activity, currently referred to as Monteregian Hills White Mountain Igneous commonwealth (MHWM), is tag at 130-100 Ma (Eby and Kennedy, 2004). The majority of the magmatism is dated to have occurred in nigh 125 Ma however, younger outliers exist (Armstrong and Stump, 1971 Foland and Faul, 1977 Eby and Kennedy, 2004). This younger activit y consists of mainly of mafic alkaline suites and felsic rocks in the intrusions and of this series, small plugs and ring like structures are twain present with the most evolved rocks being syenites and quarts with occurrences of biotite granite (Eby and Kennedy, 2004).Many geologists have hypothesized the root of the magma series. As advances in geological sciences have been made, along with advances in identification of rocks and dating, these hypotheses have evolved. Of these, one of the first major ideas include cryptical seated fractures in a northwestward and east-west trending net tempt that act as centers of low twitch and intrusions for melting (Chapman, 1968). A hypothesis of a hot spot rakehell has been back up by a greater range of geologists (Crough, 1981b Dun cease, 1984). A third major hypothesis to the introduction of the WMMS involves rifting in line with the initiative of the Atlantic (Foland and Faul, 1977 McHone, 1981 McHone and Butler, 1984). Since thither is no decisive agreement on the origin of the White Mountain Magma Series, on that point have been advances in understanding the magma sources themselves (Eby et al., 1992).The evolution of hypotheses surrounding the origin of the magmatism in the White Mountain Magma Series will be explored in this paper. The evolution of thought with incorporation of geological advances will be utilize to rule the current understanding of the White Mountain Magma Series.Formation faulting ZonesCarleton Chapman was one of the first geologists to write about the formation of the WMMS. As published, it was postulated that there are two sets of deep seated fracture zones which form a hoop within the crust of the earth under the WMMS (Chapman, 1968). In this hypothesis, these zones had a lower pressure and underwent partial melting from which mafic magma intruded via rounded chambers and move to the top of the crust (Chapman, 1968). The mapped absences of igneous activity were taken into cipher and warrant to be due to inadequate melting in a incident region, prevention from overlying rock in allowing the magma to rise to the surface were it could be mapped, and that igneous rock could have been mistakenly missed in arena work or covered by surface rock (Chapman, 1968). The lattice line structure proposed has little evidence to support it as there are no faults along the proposed structure of lines (McHone and Butler, 1984).HotspotsThe hot spot model appears in a number of papers in which the WMMS is linked to a hot spot in with the North Ameri give nonice plate moved over. An expanded magnetic declination of the simple hot spot model has been made with the addition to support of the hotspot origin of the modern England Seamount chain and the general movement of the North Ameri tail assembly plate over a hotspot (Crough, 1981b). In connecting the use of conodant, fission pass through, radiometric, and tectonic data, a hypothesis that this movement led to t he regional intoxicate of New England was developed (Crough, 1981b). This uplift was at least 4km in equality to the central Appalachian region (Crough, 1981b). Through the plotting of this data, the younger White Mountain Igneous duty forming via the Greater Meteor hotspot track is explained however, the senior Igneous Province is not accounted for in this trace (Crough, 1981b). This argument has published faults it is argued that due to lack of significant age approach there is a large data gap along the hotspot trace mingled with the province and used kimberlite and seamounts (McHone, 1981). In addition to this gap, it is pointed out that although a draw of the data does fit the hotspot model, it excludes the Older Igneous Province, leaving umteen questions as to whether this is due to a pall plunk whose trace has been erased, later magmatism, or other events not known (McHone, 1981). .In support of the hotspot hypothesis in nexus to the New England Seamount Chain, th e use of radiometric ages of K-Ar and 40Ar-39Ar were examined (Duncan, 1984). From southeast to northwest there is an increase in seamount construction leading to the northwestward enquiry of the North the Statesn plate over a New England hotspot between 103 Ma and 83 Ma (Duncan, 1984). Fitting the seamount distribution with a volcano migration rate of 4.7cm/year, the ages align with a larger age progression from the Corner Seamounts, on the east end (70 to 75 Ma) to the younger White Mountain Igneous Province (100 to 124 Ma) (Duncan, 1984). The age-space relation used does not account for the Older Igneous Province, leaving a gap in the hotspot model (Duncan, 1984).RiftingThrough the dating of 26 igneous complexes via K-Ar analysis, it was thereby govern out that the single hotspot hypothesis can account for the just formation of the WMMS as it does not account for the spread of ages, a non-consistent snip transgression from 98 to 238 Ma, nor does it account for the dates appea ring to show more occasional activity than continuous (Foland and Faul 1977). The WMMS complexes were hypothesized to have originated along the extension of a modify fault during sea-floor spreading (Foland and Faul 1977).Arguably, the younger White Mountain Igneous Province and older White Mountain Igneous Province could be initiated and positioned along weak zones of deep-seated fractures, explaining their overlap (McHone, 1981). The overlap seen in mapping of the WMMS can be stress related to the opening of the both the central Atlantic and northern Atlantic and the gradual strain along the zones caused magmatism to decrease (McHone, 1981). The regional uplift as a result of the hotspot movement (Crough, 1981b), can be accounted for by the transfer of rut into the lithosphere by intrusions (McHone, 1981). In an argument against the hypothesis of weakened zones, it is stated there is no spherical relation between volcanic lineaments and surficial features, the majority of the d ated volcanic lineaments show an age progression, midplate volcanism is not known to occur across the aforesaid(prenominal) lineaments at severalise times, and lastly three major lithospheric faults four separate periods of activation would be needed to account for all features and data (Crough, 1981a).Elaborating upon the proposed hypothesis of weakened zones due to rifting (McHone, 1981), once the Atlantic had opened, a significant bar of granitic magma and undersaturated gabbro-diorite-syenite were formed and hypothesized to be a result of melting in the thick crust caused by volatile upwelling or increased heat flow, thus creating the WMMS (McHone and Butler, 1984). The extended nature of the WMMS is proposed to be a result of chill upwelling along and extensional fracture zone in which the WMMS is a check of the orientation and positioning of a deep basement structure pair to the Connecticut River Valley and Lake Champlain Valley (McHone and Butler, 1984). At the thickest parts of this lower crust, partial melting occurred, crustal thinning and erosion were accelerated by uplift, and the WMMS was emplaced as the deep basement structures were technically active under the influence of mantle convection during rifting (McHone and Butler, 1984). reliable UnderstandingFrom geochronological data, a thermal anomaly existed for an extended period of time under the WMMS (Eby et al., 1992). The mantle source, through isotopic dating, matches characteristics similar to that of oceanic island basalt source but determining whether that source a hotspot or from rifting is not known (Eby et al., 1992). In either case, it is proposed that the mantle-derived melts were emplaced into the crust at the base and by fractional crystallization evolved and this stage was interrupted and the magmas were moved to a higher(prenominal) crustal level where later evolution took place (Eby et al., 1992).The Central Atlantic Magmatic Province ( populate)which extends to the north and south on either side of the Atlantic sea where magmatism occurred at about 200 Ma and in Maritime and New England province (CNE)this magmatism occurred between 225 and 230 Ma (Eby, 2013). This magmatism is immediately followed by the older White Mountain Igneous Province (OWM) as it a distinctly unalike emplacement of igneous rocks, from about 200 to 160 Ma and thus in roughly 122 Ma the Monteregian Hills White Mountain Igneous Province (MHWM),introduced displaying a greater range of diverse rocks (Eby, 2013). The rarity of mafic rocks in the make negates any direct comparison with CAMP magmas although, OWM samples have elemental and isotopic characteristics similar to CNE and MHWM which are drastically incompatible from that of CAMP magmas (Eby, 2013). As mafic rocks are abundant in the MHWM and these magmas have been hypothesized to be derived from a depleted mantle source and are related by degrees of melting and crustal contamination, the same models can be applied to th e OWM and CNE (Eby, 2013). It can thus be concluded that the CNE, OWN, and MHWM were all derived from a similar matching magma source and are representative of change magma compositions related to variations in degrees of partial melting and crustal contamination (Eby, 2013). It is pointed out however, this does not link CAMP magmas to these three as it must come from a separate source magma and has a different history (Eby, 2013).Using the connection made between OWN, MHWM, and CNE, a step in determining the origin of the WMMS is to determine the origin of the CNE. The CNE magmas may the start of a plume origin for the CAMP magmas however, because of the lack of relationship between the CAMP and CNE magmas this hypothesis is however to be resolved (Dorais, 2005). In assuming that the CNE magmas were the initial magmatism in a plume event, then a composition of oceanic island basalts would not be expected however that is what CNE I has as a composition (Dorais, 2005). oceanic ba salts have been hypothesized to represent the end of plume magma events and thus CNE magmas would be faux to have to have erupted after that of the plume, not prior (Dorais, 2005). It has been concluded however, that the CNE rocks may represent pre- guard type magmatism prior to CAMP as it matches elemental characteristics of Loihi magmas which were precursors to the shield magmatism in Hawaii (Dorais, 2005). With these conclusions and the connections between OWM, MHWM, and CNE it is possible that the hotspot/mantle plume hypothesis has further support.ConclusionIt is clear that there is no consume answer to how the White Mountain Magma Series was formed and how it was emplaced into its current positioning. I retrieve it is fair to say that the hypothesis of fracture zones under the province (Chapman, 1968) has little evidence to be considered a reasonable explanation. As to the palisade over whether the WMMS is a result of a hot spot track or rifting due to the opening of the A tlantic, I do not believe there is a concise answer. Both hypotheses have what seems to be logical evidence for support while they also both have flaws and unaccounted for aspects. To determine one origin hypothesis, I believe it is relevant to continue work in looking at the larger picture of the WMMS and how it is similar and different to the series of the CAMP and CNE magmas. If additional connections can be made in terms of composition and dating models then additional progress in terms of origin of both the WMMS and the CNE magmas.ReferencesArmstrong, R., Stump, E. (1971). Additional K-Ar dates, White Mountain magma series, New England. American Journal of Science, 270(5), 331-333.Chapman, C. A. (1968). A comparison of the Maine coastal plutons and the magmatic central complexes of New Hampshire. Studies in Appalachian Geology Northern and Maritime, Ed.by E-an Zen, WS White, JB Hadley and JB Thompson Jr., New York, Interscience Pubs., Inc,Crough, S. T. (1981). Comment and repl y on Mesozoic hotspot epeirogeny in eastern north America REPLY. Geology, 9(8), 342-343.Crough, S. T. (1981). Mesozoic hotspot epeirogeny in eastern North America. Geology, 9(1), 2-6.Dorais, M. J., Harper, M., Larson, S., Nugroho, H., Richardson, P., Roosmawati, N. (2005). A comparison of eastern north America and coastal New England magma suites Implications for subcontinental mantle evolution and the broad-terrane hypothesis. Canadian Journal of farming Sciences, 42(9), 1571-1587.Duncan, R. A. (1984). Age progressive volcanism in the New England seamounts and the opening of the central Atlantic Ocean. Journal of Geophysical Research Solid Earth (19782012), 89(B12), 9980-9990.Eby, G. N. Ossipee field trip guide New Hampshire geological society.Eby, G. N. (2013). Post CAMP magmatism The White Mountain and Monteregian hills igneous provinces, eastern North America.Eby, G. N., Krueger, H. W., Creasy, J. W. (1992). Geology, geochronology, and geochemistry of the White Mountain batho lith, New Hampshire. Geological Society of America Special Papers, 268, 379-398.Eby, G., Kennedy, B. (2004). The ossipee ring complex, New Hampshire. Guidebook to Field Trips from Boston, MA to Saco Bay, ME New England Intercollegiate Geological Conference, Salem, Massachusetts, pp. 61-72.Lachance, D. J. (1978). multiplication of the White Mountain magma seriesMcHone, J. G. (1981). Comment and reply on Mesozoic hotspot epeirogeny in eastern north America COMMENT. Geology, 9(8), 341-342.McHone, J. G., Butler, J. R. (1984). Mesozoic igneous provinces of New England and the opening of the North Atlantic Ocean. Geological Society of America Bulletin, 95(7), 757-765.