1. Rebuttal The Case against the Null Hypothesis of Marsh Jim Miller Department of Geological Sciences Precambrian Research Center University of Minnesota Duluth

2. Mineralogical Magazine (1996) Elements (2006) Bruce Marsh Johns Hopkins U.

3. Contributions to Mineralogy and Petrology (2013) Contributions to Mineralogy and Petrology (in press)

4. With Rais Latypov, 2005, Finland

5. Marsh’s Arguments against In Situ Crystallization Differentiation 1)Massive, undifferentiated mafic-ultramafic intrusions are common; indeed, they are the rule. 2)The abundance of homogeneous intrusions is due to crystallization from phenocryst –free basaltic magmas that are not able to differentiate in crustal chambers because evolved melts are trapped in solidificaton fronts. (Examples: Sudbury Complex and Ferrar Peneplain Sill). 3)Layered intrusions with pronounced phase and cryptic layering are attributed to the repeated emplacement of batches of magma with phenocrysts in different combinations and with varied chemical compositions (Examples – Hawaiian lava lakes, Ferrar Basement Sill, Palisade Sill)

6. Postulate 1 Massive, undifferentiated mafic-ultramafic intrusions are common By Marsh’s definition, differentiated intrusion must have produce a grantitic distillate. Bowen showed that even perfect fractional crystallization will produce a high silica liquid fractionate – and even the, it will only comprise about 5% of the total magma volume. Marsh uses whole rock SiO2, MgO, and CaO and indicators of differentiation but ignores other important indicators - phase layering, cryptic layering of solid solution minerals, enrichment in incompatible trace elements and depletion of compatible elements. Marsh ignores or reinterprets units of the Sudbury Igneous Complex that clearly indicate internal differentiation - lower mafic norite and upper quartz gabbro, and considers only whole rock MgO rather than the mg# of pyroxene.

7. Marsh’s evidence of undifferentiated mafic intrusions with late small granite segregations filling delaminated chill in the roof zone Marsh (1996)

8. Even the Sudbury Complex shows Cryptic Variation Not Differentiaton ??

9. Postulate 2 Phenocryst –free basaltic magmas are not able to differentiate in crustal chambers because evolved melts are trapped in solidification fronts In mafic intrusions of all sizes, shapes and depths of emplacement, it is clear that these intrusion show systematic differentiation whether as shown dramatically in the closed systems of the Skaergaard and Sonju Lake, or in large thick sequences like Stillwater, Bushveld and the Layered Series at Duluth. Many MLI lack an upper border series as would be expected in Marsh’s model of collapsing solidification fronts. Sonju Lake in particular can be modeled by bottom up crystallization differentiation of single evolved tholeiitic magma.

10. SiO247.6 TiO22.28 Al2O314.0 FeOt14.7 MnO0.21 MgO8.3 CaO9.4 Na2O2.47 K2O0.55 P2O50.30 Volatiles0.20 Total100.0 mg# 50.2 Sc34 V192 Cr111 Co75 Ni185 Rb20 Sr233 Ba171 Y20 Zr114 Nb17 Hf3.1 La14.7 Ce33.4 Sm 4.1 Eu1.6 Tb0.8 Yb2.1 Lu.32 Bulk Intrusion Composition = Parent Magma = moderately evolved olivine tholeiitic basalt From Miller and Chandler (1998) and Miller and Ripley (1997) Liquid Line of Descent Calculated by summing composition of rock column above a specific horizon

11. Fractional Crystallization Modelling CHAOS 2 (NIELSEN, 1990) Model Parameters : fO2 = -2 log QFM; trapped liquid = 20%

12. Postulate 3 Layered intrusions with pronounced phase and cryptic layering are attributed to the repeated emplacement of batches of magma with phenocrysts in different combinations and with varied chemical compositions How did these crystal slurries of varied composition acquired their variability if not by differentiation in some ficticous magma chamber at depth? It is paradoxical that even in the case of the largest known intrusion of largely basaltic composition, most of the fractional crystallization reflected in the cryptic compositional trends of the layered sequence has to be relegated to conjectural processes that took place in an underlying (and possibly even more voluminous) chamber How can the random input of varied crystal slurry compositions create a systematic phase stratigraphy commonly observed in both closed and open system intrusions? Why aren’t porphyritic basalts more common in LIPs hosting many differentiated layered intrusions – e.g. the MCR? And why are they typically dominated by only Pl phenocrysts?

13. From Latypov (2009)

14. “An attempt is made at the outset to provide a list of inviolate Magmatic First Principles that are relevant to analyzing most magmatic problems. These involve: initial conditions; critical crystallinity; solidification fronts; transport and emplacement fluxes; phenocrysts, xenocrysts, primocrysts; crystal size; layering and crystal sorting; thermal convection; magmatic processes are physical”. Bruce Marsh, 2013 The High Priest of Magmatology

15. “It could be argued that regular, cryptically varying series of crystal mushes were successively injected, rather than liquids, which is equivalent to agreeing that layered intrusions existed, but with the unusual reservation that they always lay below the levels of present-day exposures. The regularity of the cryptic variation of many layered intrusions is particularly difficult to explain according to the idea of continuous tapping of a deeper magma reservoir, for it implies that the complete crystallization record of a deep-seated intrusion was transferred, stage by stage, to a higher level intrusion”. Lawrence Wager and Malcolm Brown (1968, p. 546) Wager and Brown actually considered the Sequential Slurry Model, but found it wanting because of chemical evidence and too much coincidence.

16. Other Issues with Marsh’s (2013) Claims The views of Wager and Brown (1968) Marsh (2013, p. 669) attributes the improbable scenario of instantaneous emplacement of crystal-free magma for the origin of the Skaergaard, Stillwater and Bushveld intrusions to Wager and Brown. Although they ascribed emplacement of the Skaergaard to be a geologically rapid event of one magma batch, in the case of the Bushveld intrusion, they state that it was “unlikely that the act of magma injection was a single incident” (p. 404) and they encompassed the idea of “stages when fresh supplies of basaltic magma entered the chamber from below”

17. Other Issues with Marsh’s (2013) Claims Mineral-Melt Reactions Marsh (2013) makes the curious statement (on p. 685) that “For magma to differentiate by fractional crystallization crystals must be available to react with the melt, the ultimate origin of the crystals is almost immaterial.” This is diametrically at odds with conventional wisdom: fractional crystallization is a consequence of the physical and/or kinetic isolation of crystals from their parent melt so that such a reaction is inhibited

18. Other Issues with Marsh’s (2013) Claims Misinterpretation of Bowen’s Reaction Series Marsh’s view (on p. 666) that Bowen’s “reaction series became synonymous with fractional crystallization”. As Bowen (1928) was at pains to point out, the portrayal of “reaction series” incorporated into Figure 9 of Marsh (2013) principally expresses the relationship between mineral phases and generalized crystallization temperature. Mineral-melt reactions are in fact part and parcel of equilibrium crystallization whereas in perfect fractional crystallization they are prohibited.

19. Other Issues with Marsh’s (2013) Claims Size of Crystals in Sills and Layered Intrusions Marsh (1996) points out that many mafic sills contain dense basal accumulations of large (2-10 mm) olivine or orthopyroxene phenocrysts and suggest that the size of these crystals alone preclude them from having grown in situ. In his new paper, Marsh (2013) makes the additional claim that “The crystals in Skaergaard…..are too large to have grown in a body of this size”. In particular, Marsh (2013) proposes a simple model of kinetic crystal growth that does not take into account the role of equilibration (coarsening) that is so important in the postcumulus textural development of most plutonic rocks (Higgins 2011).

20. Other Issues with Marsh’s (2013) Claims Size Distribution of Crystals in Sills and MLI Skaergaard Intrusion and Palisades Sill both have upper border sequences that are compositionally mirror images of their extensively differentiated, and significantly thicker, lower sequences. In both the Skaergaard (Naslund 1984) and the Palisades (Hristov and Naslund 1994), rocks in the upper border sequences are 2 to 3 times coarser-grained than the time-equivalent lower sequences. If in situ crystallization is disallowed, then the formation of these two intrusions by multiple injections of crystal slurries must have involved sinking of the smaller crystals and floating of the larger crystals, which is exactly the opposite of what would be predicted by the crystallization front capture model of Marsh (2013).

21. Other Issues with Marsh’s (2013) Claims Kilauea Lava Lake Marsh (2013) presents the Kilauea Iki lava lake as an ‘end- member’ example of differentiation by simple accumulation of crystals transported in the lava. Recent research suggests, however, that filling and solidification of the lake may be complex (Vinet and Higgins 2011). Olivine CSDs are almost uniform throughout the lake and show no significant variation in slope that would indicate that settling has occurred. Furthermore, a detailed inventory of the zoning and deformation of olivine crystals suggests that the lake was partly filled from the base and that bulk compositional variations may be a relic of this process (Vinet and Higgins 2011).

22. Other Issues with Marsh’s (2013) Claims Evidence for In Situ Fractional Crystallization Marsh (2013) presents the Kilauea Iki lava lake as an ‘end- member’ example of differentiation by simple accumulation of crystals transported in the lava. Recent research suggests, however, that filling and solidification of the lake may be complex (Vinet and Higgins 2011). Olivine CSDs are almost uniform throughout the lake and show no significant variation in slope that would indicate that settling has occurred. Furthermore, a detailed inventory of the zoning and deformation of olivine crystals suggests that the lake was partly filled from the base and that bulk compositional variations may be a relic of this process (Vinet and Higgins 2011).