Table 1 Results of least-squared mass balance calculations.

From: Gravity modeling finds a large magma body in the deep crust below the Gulf of Naples, Italy

Transition from shoshonitic basalt to trachy-basalt (step 1)
Sample	APR 22	APR 19
Composition	Shoshonitic basalt parent magma measured wt.%	Trachy-basalt daughter magma measured wt.%	Difference between parent and daughter magmas:
Composition	Shoshonitic basalt parent magma measured wt.%	Trachy-basalt daughter magma measured wt.%	observed	calculated	obs.-calc. (residuals)
SiO₂	46.22	49.04	1.43	1.31	0.12
TiO₂	1.20	1.28	0.04	0.25	−0.21
Al₂O₃	15.05	17.19	1.68	1.70	−0.02
Fe₂O₃tot	8.72	8.68	−0.31	−0.23	−0.08
MnO	0.14	0.14	0.00	−0.40	0.40
MgO	9.71	6.33	−3.68	−3.66	−0.02
CaO	11.46	11.37	−0.44	−0.33	−0.11
Na₂O	2.80	3.10	0.22	0.63	−0.41
K₂O	1.45	2.44	0.95	0.60	0.35
P₂O₅	0.31	0.43	0.11	0.11	0.00
H₂O	2.49
CO₂	0.46
Total	100.01	100.01
			Sum of the squares of residuals		0.52
Subtracted minerals			Amounts relative to initial magma vol.%		Absolute amounts vol.%
Clinopyroxene (Wo₄₇En₄₆)			10.72		41.38
Olivine (Fo₈₉)			7.44		28.72
Plagioclase (An₇₂Ab₂₅)			5.55		21.44
Cr-spinel (Cr# 0.53)			2.19		8.46
Total relative to initial magma			25.90		100.00
Transition from trachy-basalt to shoshonite (step 2)
Sample	APR 19	97 119 21a
Composition	Trachy-basalt parent magma measured wt.%	Shoshonite daughter magma measured wt.%	Difference between parent and daughter magmas
Composition	Trachy-basalt parent magma measured wt.%	Shoshonite daughter magma measured wt.%	observed	calculated	obs.-calc. (residuals)
SiO₂	49.04	49.69	2.35	1.92	0.42
TiO₂	1.28	0.82	−0.43	−0.03	−0.40
Al₂O₃	17.19	15.80	−0.85	−0.97	0.12
Fe₂O₃tot	8.68	7.91	−0.50	−0.82	0.32
MnO	0.14	0.13	−0.01	−0.33	0.32
MgO	6.33	5.53	−0.61	−0.69	0.08
CaO	11.37	10.40	−0.61	−0.63	0.02
Na₂O	3.10	2.09	−0.94	−0.49	−0.45
K₂O	2.44	3.79	1.49	1.74	−0.25
P₂O₅	0.43	0.52	0.12	0.29	−0.17
H₂O		3.27
CO₂		0.30
Total	100.01	100.25
			Sum of the squares of residuals		0.86
Subtracted minerals			Amounts relative to initial magma vol.%		Absolute amounts vol.%
Plagioclase (An₄₆Ab₄₇)			29.77		56.02
Clinopyroxene (Wo₄₈En₄₁)			15.41		28.98
Olivine (Fo₈₉)			3.22		6.06
Ti-magnetite (Usp₂₇)			3.15		5.92
Cr-spinel (Cr# 0.53)			1.61		3.02
Total relative to initial magma			53.16		100.00
Transition from shoshonite to latite (step 3)
Sample	97 119 21a	97 101 FRb
Composition	Shoshonite parent magma measured wt.%	Latite daughter magma measured wt.%	Difference between parent and daughter magmas
Composition	Shoshonite parent magma measured wt.%	Latite daughter magma measured wt.%	observed	calculated	obs.-calc. (residuals)
SiO₂	49.69	53.05	4.00	4.11	−0.11
TiO₂	0.82	0.75	−0.07	−0.08	0.01
Al₂O₃	15.80	17.42	1.84	1.87	−0.03
Fe₂O₃tot	7.91	7.01	−0.86	−0.79	−0.07
MnO	0.13	0.12	0.00	−0.04	0.04
MgO	5.53	2.19	−3.43	−3.43	0.00
CaO	10.40	5.26	−5.27	−5.28	0.01
Na₂O	2.09	4.03	2.05	1.87	0.18
K₂O	3.79	5.45	1.76	1.65	0.11
P₂O₅	0.52	0.50	−0.03	0.12	−0.15
H₂O	3.27	4.00
CO₂	0.30	0.20
Total	100.25	99.99
			Sum of the squares of residuals		0.08
Subtracted minerals			Amounts relative to initial magma vol.%		Absolute amounts vol.%
Clinopyroxene (Wo₄₈En₄₁)			25.95		41.95
Plagioclase (An₇₂Ab₂₅)			17.32		27.99
Alkali-feldspar (Or₈₆Ab₁₃)			12.16		19.66
Ti-magnetite (Usp₂₇)			3.07		4.96
Olivine (Fo₈₀)			2.88		4.66
Apatite			0.48		0.78
Total relative to initial magma			61.86		100.00
Transition from latite to trachyte (step 4)
Sample	97 101 FRb	SsB2
Composition	Latite parent magma measured wt.%	Trachyte daughter magma measured wt.%	Difference between parent and daughter magmas
Composition	Latite parent magma measured wt.%	Trachyte daughter magma measured wt.%	observed	calculated	obs.-calc. (residuals)
SiO₂	53.05	56.75	4.66	4.66	0.00
TiO₂	0.75	0.42	−0.33	−0.49	0.16
Al₂O₃	17.42	17.58	0.42	0.41	0.01
Fe₂O₃tot	7.01	4.40	−2.66	−2.64	−0.02
MnO	0.12	0.12	0.00	−0.03	0.03
MgO	2.19	0.57	−1.69	−1.64	−0.05
CaO	5.26	2.56	−2.78	−2.79	0.01
Na₂O	4.03	4.01	0.03	0.12	−0.09
K₂O	5.45	7.97	2.74	2.75	−0.01
P₂O₅	0.50	0.13	−0.38	−0.35	−0.03
H₂O	4.00	5.00
CO₂	0.20	0.05
Total	99.99	99.56
			Sum of the squares of residuals		0.04
Subtracted minerals			Amounts relative to initial magma vol.%		Absolute amounts vol.%
Plagioclase (An₃₂Ab₅₆)			25.45		41.64
Alkali-feldspar (Or₅₁Ab₄₄)			16.92		27.68
Clinopyroxene (Wo₄₈En₄₁)			8.75		14.32
Ti-magnetite (Usp₂₇)			4.65		7.61
Biotite			4.31		7.06
Apatite			1.04		1.69
Total relative to initial magma			61.12		100.00

Calculations have been carried out through the XLFRAC software⁸⁴. Rocks and mineral phases compositions are from²⁹ and references therein. The volatile contents do not take part in mass balance calculations, and the major oxides are recalculated to 100 % on volatile-free basis.

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Table 1 Results of least-squared mass balance calculations.

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