Petrography and genesis of a wollastonite body and its associated rocks at Holyoake Valley, Nelson, New Zealand

Abstract

Samples from a wollastonite-rich lens, up to 55 m long and 10 m wide, within the contact aureole of the Canaan Granodiorite at Holyoake Valley, include a variety of calc-silicate rocks which locally contain abundant titanite. The mineralogy of the contact rocks indicates hornblendehornfels facies conditions during metamorphism. Within the wollastonite body, an intrusive vein of monzonitic composition, up to 2 m across, probably resulted from crystallisation of granodioritic magma modified by partial desilication and contamination from adjacent calcium-rich rocks. Zoned calc-silicate rocks, apparently formed by reaction between wollastonite and basic hornfels that had been produced by recrystallisation of a dike of probable basaltic composition, are also present. Late intrusion of small amounts of quartzofeldspathic magma took place along discontinuities, including the dike boundaries, within and adjacent to the wollastonite body. Iron and titanium metasomatism was probably associated with intrusion of the quartzofeldspathic magma, while diffusion of calcium towards it led to the formation of heterogeneous contaminated rocks interpreted as endoskarns.Available evidence is insufficient to allow a decision to be made between formation of the wollastonite by reaction between marble and enclosed quartz-rich layers or lenses, or by introduction of silica into marble from the adjacent granodiorite magma. Formation of the contact rocks probably took place with low values of XCO 2 relative to XH 2 O in the fluid phase. Late changes accompanying cooling of the contact rocks in the presence of a fluid with high XH 2 O resulted in the crystallisation of small amounts of retrograde vesuvianite, prehnite, and apophyllite.

Simultaneous Magmatic and Hydrothermal Regimes in Alta–Little Cottonwood Stocks, Utah, USA, Recorded Using Multiphase U-Pb Petrochronology

“…Titanite paragenesis in calc-alkaline rocks is more complex, and as mentioned above, titanite (re)crystallizes via multiple processes, such as de novo crystallization from melt [62], redox reactions involving Fe-Ti oxides [58], and/or (re)crystallization in the presence of fluids [63]. Titanite is stable in calc-silicate skarns [64][65][66] and often grows due to the breakdown of Ti-bearing clinopyroxene, and may (re)crystallize during the infiltration of fluorine and/or H2O-rich fluids [50,67,68]. Photographs and interpretation schematics showing the highly composite nature of the magmatic and hydrothermal system.…”

Product Stewardship in Wollastonite Production

“…Numerous sources were consulted in the preparation of this table. These sources include Burnham, 1995;Crooks, 1999;DeRudder and Beck, 1962;Dumont, 2005;Grammatikopoulos et al, 2003;Higgins et al, 2001;Johnson, 2003;Lueck, 1997;Orris and Bliss, 1991;Pawley et al, 1996;Simandi et al, 1999;Strunz and Nickel, 2000;Virta, 2005a;Virta, 2005b;Watters, 1995;Yang and Prewitt, 1999; Amethyst Galleries, Inc., available online at http://www.galleries.com/minerals/silicate/ wollasto/wollasto.htm; www.britannica.com; webmineral.com; mineralszone.com; smartmineral.com; mindat.org (for example, see actinolite at http://www.mindat.org/min-18.html); Mineral Data Publishing, available online at http://rruff.geo.arizona.edu/doclib/ hom/wollastonite.pdf. beneficiated by wet high-intensity separation to remove iron oxides (Dumont, 2005).…”

“…Leading world producers in 2005 ranked in descending order of wollastonite output include China (395,000 tonnes), India (169,000 tonnes), the United States (115,000 to 127,000 tonnes), Mexico (27,100 tonnes), and Finland (16,800 tonnes) (Virta, 2005a). Potentially economic deposits have been identified (and some actually mined) in Australia, Brazil, Canada Chile, Cuba, Czech Republic, Greece, Kenya, Morocco, Namibia, New Zealand, North Korea, Pakistan, Japan, Spain, Turkey, and Uzbekistan (Crooks, 1999;Dumont, 2005;Fattah, 1994;Lueck, 1997;Palfi, 2002;Parkison, 1990;Virta, 1994Virta, , 2003Watters, 1995).…”