Wollastonite- anorthite- gehlenite-, and fassaite

American Mineralogist, Volume 90, pages 1926–1933, 2005
REPLY TO STOPPA ET AL. 2005
Wollastonite- anorthite- gehlenite-, and fassaite-bearing rocks: Igneous petrological oddity
or paralavas?
LEONE MELLUSO,1,* SANDRO CONTICELLI,2,† MASSIMO DʼANTONIO,1 NICOLETTA P. MIRCO,3 AND
EMILIO SACCANI4
2
1
Dipartimento di Scienze della Terra, Università degli Studi di Napoli Federico II, Via Mezzocannone, 8, I-80134, Napoli, Italy
Dipartimento di Scienze della Terra, Università degli Studi di Firenze, and Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle
Ricerche, Via G. La Pira, 4, I-50121, Firenze, Italy
3
Via V. Monti, 1R, I-50124, Firenze, Italy
4
Dipartimento di Scienze della Terra, Università degli Studi di Ferrara, Corso Ercole I dʼEste 32, I-44100 Ferrara, Italy
ABSTRACT
We brießy review the petrological and geochemical features, and physical characteristics, of
the Colle Fabbri and Ricetto rocks to discuss their possible paramagmatic origin, i.e., derived from
complete melting, after devolatilization, of marly protoliths, without any orthomagmatic, ultimately
mantle-derived, chemical or thermal input. Contrary to the various comments that have been made,
the overall mineralogical, petrological, and geochemical data provided in the literature well agree
with this Þnding.
INTRODUCTION
The Colle Fabbri outcrop of massive, and scoriaceous rocks
has attracted the attention of researchers about its ultimate
nature. Ricci (1882), during Þeld research prior to opening
the Lignite mine beneath Colle Fabbri, mapped this rock and
called it “marna rossa combusta” (i.e., “Red burnt Marlstone”).
Stoppa (1988) attributed to this outcrop a mantle-derived nature,
naming the rock Þrst “euremite,” then carbonatite, and Þnally
uncompahgrite. Stoppa et al. (2005) suggested a further new
name for this rock: leucite-wollastonite melilitolite. Melluso et
al. (2003) showed that the main rock type at the Colle Fabbri
outcrop (i.e., euremite/carbonatite/uncompahgrite/melilitolite
beneath the Bocchini House; see Fig. 1 of Stoppa et al. 2005)
has a complex and strongly variable mineralogy, paragenesis, and
chemistry, which follow a trend straddling at least two thermal
barriers in relevant orthomagmatic systems. On this basis, Melluso et al. (2003) interpreted its genesis from a completely different point of view, making inferences about the paramagmatic
(i.e., pyrometamorphic) nature of the outcrop, and endorsing the
primordial hypothesis of Ricci (1882). In our opinion, the data reported in the comment of Stoppa et al. (2005) strengthen—rather
than weaken—the Þndings about the pyrometamorphic nature
of the Colle Fabbri rock.
In this note, we will refer mainly to the wollastonite-, gehlenite-, anorthite-, and fassaite-bearing rock found at Colle
Fabbri, and particularly to the rock making the innermost portion of the entire outcrop, the so-called “euremite” (Stoppa 1988;
Melluso et al. 2003; Stoppa et al. 2005), and we will not deal with
* E-mail: [email protected]
† E-mail: [email protected]Þ.it
0003-004X/05/1112–1926$05.00/DOI: 10.2138/am.2005.453
1926
the genesis of the Italian potassic rocks, which have been widely
discussed in the recent International literature (e.g., Cox et al.
1976; Barbieri et al. 1979; Civetta et al. 1981; Peccerillo 1985,
1998, 1999, 2001, 2003; Peccerillo and Manetti 1985; Rogers
et al. 1985; De Fino et al. 1986; Peccerillo et al. 1987, 1988;
Di Girolamo and Morra 1988; Clausen and Holm 1990; Beccaluva et al. 1991, 2002; Conticelli et al. 1991, 1992, 1997, 2002;
Conticelli and Peccerillo 1992; Stoppa and Lavecchia 1992; Di
Girolamo et al. 1995, 1999; Ayuso et al. 1998; Conticelli 1998;
Peccerillo 1999, 2003; Downes et al. 2002; Gasperini et al. 2002;
Bell 2003; Bell et al. 2003; Perini et al. 2003, 2004). Nor will we
consider the so-called Italian carbonatites, which also have been
debated extensively in the recent literature, where several compelling doubts have been raised as to their ultimate nature (e.g.,
Barker 1996; Peccerillo 1998, 2004; Downes et al. 2002) but, to
date, understated. In addition, we will not take into consideration
the wollastonite-, plagioclase-, and gehlenite-bearing rock found
at Ricetto, which shows strong mineralogical and compositional
similarities with the Colle Fabbri one, and for which there is a
general consensus regarding its pyrometamorphic nature (Melluso et al. 2003, 2005; Capitanio 2005; Capitanio et al. 2004;
Stoppa et al. 2005).
OCCURRENCE AND SAMPLES
The Ricetto and Colle Fabbri rocks have many similarities
on the basis of petrological and compositional characteristics
(Melluso et al. 2003, 2005). Regarding their geological setting,
however, the only common characteristic is that they are found
well within the Apennine chain. The Colle Fabbri paralava, which
is the argument of the present reply, is found in an intrapennine basin, well within one of the most important Italian lignite
mining districts: the “Bastardo Mine,” which has been mined