Sampling and major element chemistry of the recent (A.D. 1631-1944 ) Vesuvius activity

Journal of Volcanology and Geothermal Research, 58 (1993) 273-290 273 Elsevier Science Publishers B.V., Amsterdam

Sampling and major element chemistry of the recent (A.D. 1631-1944 ) Vesuvius activity

Harvey E. Belkin a, Christopher R.J. Kilburn b and Benedetto de Vivo c aMail Stop 959. U.S. Geological Survey, Reston, VA 22092, USA

bOsservatorio Vesuviano, Centro di Sorveglianza, I "ia Manzoni 249. 80123 Napoli, Italy ' Dipartirnento di Geofisica e Vulcanologia, Universitgt di Napoli "Federico H", Largo S. Marcellino 10, 80138 Napoli, Italy

(Received May 4, 1992; revised version accepted February 8, 1993 )

ABSTRACT

Detailed sampling of the Vesuvius lavas erupted in the period A.D. 1631-1944 provides a suite of samples for compre- hensive chemical analyses and related studies. Major elements (Si, Ti, AI, Fe t°tal, Mn, Mg, Ca, Na, K and P), volatile species (C1, F, S, H20 +, H20- and CO2), and ferrous iron (Fe z+ ) were determined for one hundred and forty-nine lavas and five tephra from the A.D. 1631-1944 Vesuvius activity. The lavas represent a relatively homogeneous suite with respect to SiO2, TiO2, FeO t°tal, MnO and P205, but show systematic variations among MgO, K20, Na20, A1203 and CaO. The average SiO2 content is 48.0 wt.% and the rocks are classified as tephriphonolites according to their content of alkalis. All of the lavas are silica-undersaturated and are nepheline, leucite, and olivine normative. There is no systematic variation in major-element composition with time, over the period A.D. 1631-1944. The inter-eruption and intra-eruption compositional differences are the same magnitude. The lavas are highly porphyritic with clinopyroxene and leucite as the major phases. Fractionation effects are not reflected in the silica content of the lavas. The variability of MgO, K20. Na20, and CaO can be modelled as a relative depletion or accumulation of clinopyroxene.

Introduction

The A.D. 1631 e rup t ion o f Vesuvius em- phat ical ly m a r k e d the beginning of more t han 300 years o f near ly cons tan t erupt ive activity. The succeeding act ivi ty was p redomina te ly effusive wi th only m i n o r pyroclast ic events, usually at the end of an erupt ive cycle. This con- t inuous act ivi ty m a d e Vesuvius an ideal labora tory for volcanologists and petrologists dur ing this per iod unti l its last e rupt ion of A.D. 1944 (e.g., Johns ton-Lavis , 1884; Washing- ton, 1906; Barberi et al., 1981; Santacroce, 1987). This report , part o f an ongoing s tudy on the petrogenesis o f the A.D. 1631-1944 Ve- suvius act iv i ty (Belkin et al., 1991 ), discusses the sampling, presents the sample locat ion maps, and considers the ma jo r -e l emen t chemistry. The da ta genera ted by this comprehen-

sive sampling and analyt ical (major , minor , and trace e lements ) p rogram have prov ided a uni f ied database for petrologic analysis (Vil- l eman t et al., 1993-this v o l u me ) , pe t rography (Trigila and De Benedet t i , 1993-this v o l u me ) , and fluid inclusion studies (Vaggelli et al., 1992, 1993-this vo lume) .

Geologic setting

Mt. Somma-Vesuvius , part o f the R o m a n potassic province (Washington , 1906), is located east o f Naples, at the southern b o u n d a r y o f the C a m p a n i a n plain. It is a composi te vol- cano tha t has erupted si l ica-undersaturated and potass ium-r ich lavas and pyroclast ics for at least 25,000 years. The erupt ive his tory o f Somma-Vesuvius can be d iv ided into three pe- riods: ( 1 ) the early historic per iod before the

0377-0273/93/$06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved. SSI)I 0377-0273 (93)E0030-6

274 H.E BELKIN EI ¢.L.

A.D. 79 "Pompei" plinian eruption; (2) the middle period covering A.D. 79 to 1631; and ( 3 ) the recent activity from A.D. 1631 to 1944. The most recent eruptive period represents an almost continuous series of mild, mostly effusive eruptions of lavas that range in composition from phonolitic-leucitite to tephritic-leucitite. The proximity of Vesuvius to the resources and study of renaissance and post- renaissance Europe plus recent detailed map- ping (Rosi et al., 1987) has provided historical documentation for the reconstruction of this recent period unparalleled for most other active volcanoes. We have used as a base for

sampling (Fig. 1 A-D) the recent map of Rosi et al., (1987). A recent compilation and discussion of the eruptive history, chemistry, petrography, and geophysics of Mt. Somma-Ve- suvius can be found in Santacroce ( 19871 and references therein.

The flows consist of pahoehoe and aa lavas; aa varieties predominating. They are homogeneous in appearance, either vesicular or mas- sive, with well developed leucite or pyroxene phenocrysts. Arn6 et al. (1987) have divided the recent period of activity into 18 eruptive cycles. These cycles start with the A.D 1638 effusive activity. The question of the existence

SAMPLING AND MAJOR-ELEMENT CHEMISTRY OF VESUVIUS (A.D. 1631-1944) 275

EXPLANATION

Lava f low boundary

I I Tyrrhenian Sea Gulf of Naples

1 I Undifferentiated products of Vesuvius and Mt. Somma

Volcanic products of the period A.D. 1944-1637

Volcanic products before A.D. 1631 and after A.D. 79orA.D, 1631

i I Parasitic vents ,[spatter and cinder cones)

Road

. . . . . Eru0tive fractures and "clefts" of the Gran Cono

~-~ J- Mt. Sommacaldera rim

1944 crater

..... ' 1906 crater

1944 Date of lava f low

I~. Volcanic vents

.i" Buried volcanic vents

• Sample Iocahon V39

[ ] Quarry

,- City

Fig. 1. Sample location maps and explanation adapted from the geological base map of Rosi el al.. 1087. The perhnenl area has been divided up into three sections noted in Fig. 1D ( Explanation ). Rosi et al.'s ( 1987 ) map has been simplified in terms of the map patterns that distinguish the volcanic products of the period A.D. 1637-1044. Scale 1:60,000. Appen- dix .k gives the details of the locations.

of lavas erupted with the A.D. 1631 explosive activity is controversial (c.f., Rosi et al., 1993- this volume: Rolandi et al., 1993-this volume). For the purpose of this report, we con- sider those rocks identified as pre-A.D. 1631 by Rosi et al. (1987) to be A.D. 1631 lavas (Figs. I A - D ) . The lavas identified as A.D. 1631 (Table 1 ) cannot be distinguished from

subsequent rocks on the basis of their major- element chemistry.

Methods

Sampling

Representative samples of bedrock or quarry outcrops were collected, labelled, and located

276 H.E. BELKIN k | AL.

TABLEI

Representative analysis of A.D. 1631-1944 Vesuvius lavas. The data for the major elements and volatiles are given m wt.% to two decimal places except SIO2, A1203, and FeO. Listed from the oldest to the youngest date of eruption and within each date. listed by decreasing MgO value. The Fe203 reported in the table was derived by the following equation: Fe203 = Fe203 t°tal - ( FeO × 1.1113 ). Values reported as upper limits (e.g., < 0.01 ) are included but were at or below the i nd ica ted detection limit.

Sample: V4 V6 V3 V2 V10 V8 VI4 V15 V16 V17 v!(~ Date A.D.: 1631 1631 1631 1631 1694 1694 1697 1697 1714 1714 i?',7

SiO2 48.2 47.5 48.4 48.4 48.1 48.0 47.6 47.7 48.3 48.2 48.~) TiO2 0.96 1.01 0.93 0.92 0.99 0.99 1.04 1.04 0.98 0.97 11.,)(, AlzO3 14.9 17.3 17.7 17.8 16.6 17.5 17.1 17.1 16.0 17.1 it;.() Fe203 5.33 5.03 3.16 4.37 4.06 7.33 3.15 2.85 3.55 3.62 5 66 FeO 2.5 3.4 4.7 3.6 4.0 1.1 5.0 5.3 4.4 4.3 2. < MnO 0.14 0.15 0.15 0.15 0.14 0.15 0.14 0.15 0.14 0.14 :).t5 MgO 6.55 4.31 3.69 3.68 5.05 4.32 4.48 4.46 5.55 4.77 ; . ~ CaO 11.8 9.81 8.44 8.33 10.2 9 15 9.92 9.94 11.0 9.69 5.44 Na20 1.78 2.22 2.63 2.72 2.42 2.48 2.37 2.36 1.96 2.52 .-.5(, K20 6.20 7.12 7.89 8.0b 6.80 7.13 7.22 7.17 6.48 6.80 v v~ H20 ~ 0.28 0.28 0.47 0.41 0.16 0.14 0.12 0.35 0.31 0.36 ~L3~ H20 0.05 0.06 0.12 0.22 0.08 0.04 0.10 0.03 0.03 0.10 .. ~,.fll P205 0.81 0.92 0.79 I).78 0.89 0.91 0.96 0.95 0.78 0.88 ,).89 CO: 0.02 0.01 0.02 <0.01 0.01 0.04 0.01 0.01 <0.01 0.01 :~.~)i F 0.21 0.22 0.26 0.25 0.19 0.27 0.25 0.22 0.18 0.19 I).24 CI 0.16 0.48 0.55 0.05 0.34 0.23 0.44 0.41 0.27 0.29 ~L3,~ S <0.01 <0.01 <0.01 <0.01 0.02 0.03 0.03 <0.01 <0.01 <-0.01 -~)01

-O= F.CI.S 0.12 0.20 0.23 0.12 0.18 ().19 0.24 0.19 0.14 0.15 ~ i ~

Total 99.77 99.62 99.66 99.62 99.88 90.62 99.70 99.85 99.79 09.80 'J~.5 i

Fe3+/Fe 2+ 1.9 1.3 0.6 11 0.9 0.0 0.6 0.5 0.7 0.8 _'.()

Sample: V19 V20 V23 V2i V27 V25 V29 V28 V30 V37 ~. 5~, Date A.D.: 1717 1723 1737 1737 t751 1751 1754 1754 1754 1760 !76()

SiO2 48.2 47.7 47.9 47~7 48.3 48.3 48.2 48.2 49.3 48.1 TiO2 0.97 1.00 0.97 (I.97 0.98 0.98 0.99 0.85 0.71 ()97 A1203 18.0 16.6 )7.5 17.6 16.11 16.1 16.9 18.9 19.~ 14. l Fe203 3.12 3.72 3.93 7.68 5.14 3.33 2.17 6.40 4.37 2.55 FeO 4.8 4.8 4.4 1.0 3.0 4.6 5.7 1.7 2.0 5.0 MnO 0.15 0.15 0.15 0.15 0.13 0.14 0.14 0.15 0.15 0.14 MgO 3.75 4.91 3.90 3.83 5.59 5.51 4.91 3.08 1.96 7.19 CaO 8.57 10.7 9.14 9,03 II.00 10.9 10.0 8.09 7.17 13.0 Na20 2.42 2.13 2.47 2.44 1.69 !.82 2.46 2.87 3.31 1.~I K20 7.96 6.43 7.45 "7.36 6.35 h.50 6.59 7.86 8.56 5.34 H20 + 0.47 0.36 0.33 0.28 0.34 0.24 0.32 0.13 0.35 0.45 H20- 0.02 0.14 <0.01 0.19 0.16 0.15 0.07 0.16 0.07 0.08 P205 0.90 0.86 0.86 0.85 0.79 0.79 0.89 0.72 0.40 0.81 ( '02 0.01 0.05 0.02 0.04 0.01 (I.01 0.01 0.06 <0.01 0.02 F 0.22 0.17 0.22 0.23 0.15 0.18 0.18 0.18 0.15 0.13 CI 0.35 0.20 0.49 0.37 0.13 0.19 0.25 0.61 0.45 0.20 S <0.01 <0.0 t <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 ~.0.01

4,x!)

- 4 4

4.14

11 t)

').48 'Lii ~,.84 • ;' ()1 ,~.12 ~).30 ~).01

-O = F.CI,S 0.17 0.12 0.20 0.18 0. t0 0.12 0.13 0.21 0.16 0. tl ') !2

Total 99.73 99.80 99.53 99.54 99.66 99.62 99.64 99.75 99.19 99.7t~ ,~, ~l

FeS+/Fe -'+ 0.6 0.7 0.8 6.9 1.5 tL v 0.3 3.4 1.5 IL5 -~

-n

,-t

+ ~

II

~ D

,+

o,8

oo

o

+ ,+

A

o

,o

o

>0

0

_:

++

g

+

0

.~

o~

,.+

o~

,.+

~N

~,.

+o

;++

.+~

++

.+,~

_

_ _

_

A

si_

~i,

~c

,~:b

~;.

+.+

bb

, i,

+i,

+:

b,

tob

~',

D',

~

A

__

,.

~

+,.

I < ,.

i o

~

~o -<

%

+ r~

~o

o~

_ ~ o

~o

~o

~o

~~

~

A

__

-~

~X

-~

'~

~

'~

~ o

Po

Po

PP

P~

H~

Po

~P

Pm

~

A

__

w

~ o

pp

po

:p

p~

!~

p~

pp

p~

:~

~

~ 0

l~

tO

0 0

I-Q

9

t~

q 0

~ ~

; 0

q 0

~

A

~ ~

o o

~ ~

o o

o c

o.~

, --

:~

9

~ ~

'~'.

~.o

~

,...,

~ _

__

_~

,.

.,

~o

~o

,.

-,

~~

,-

-ff

~<

~<

~<

s+<+

} rl P1

-)

r'

i1

.+ < } rl

< < ;+ 4

278

TABLE 1 ( c o n t i n u e d )

H.E. BELKIN E1 AI.

Sample: V67 V66 V72 V70 V77 V74 V75 V78 V80 V82 ,v ~4 Date A.D.: 1839 1839 1850 1850 1855 1855 1855 1855 1858 1858 :~61

SiO2 47.4 47.4 47.6 48.0 47.5 47.5 47.3 47.6 47.6 TiO2 1.04 1.03 1.01 i,01 1.03 1.03 1.04 1.00 1.08 A1203 17.6 17.7 16.2 18.6 16.3 16.5 16.8 18.7 17.6 Fe203 4.62 3.86 4.37 4.63 3.12 2.84 5.32 5.01 2.08 FeO 3.8 4.5 3.9 3.7 5.0 5.3 3.1 3.5 6.2 MnO 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.16 0.15 MgO 4.06 3.99 5.31 3.47 5.27 5.11 4.72 3.20 4.20 CaO 9.60 9.44 11.2 8.02 10.9 10.8 10.3 8.54 9.20 Na20 2.58 2.62 2.19 2.62 2.43 2.46 2.42 2.66 2.65 KzO 7.16 7.21 6.29 7.76 6.46 6.50 6.69 7.62 7.27 H20 ÷ 0.33 0.34 0.16 0.17 0.19 0.08 0.34 0.33 0.34 H20- 0.30 0.34 0.56 0.63 0.59 0.39 0.40 0.39 0.11 P205 0.89 0.89 0.83 0.84 0.84 0.84 0.84 0.82 0.99 COe 0.01 0.01 0.03 0.01 0.02 0.01 0.05 0.03 /).03 F 0.21 0.23 0.21 0.31 0.24 0.23 0.20 0.23 0.33 CI 0.40 0.46 0.29 0.37 0.42 0.40 0.47 0.26 0.27 S <0.01 <0.05 <0.01 0.02 0.03 < 0.01 <0.01 <0.01 0 13i

-O=F,CI ,S 0.18 0.22 0.15 0,24 0.23 0.19 0.19 0,16 0.22

Total 99.97 99.48 100.14 100.07 100.27 99.95 99.95 99.89 99.9o

FeS+/Fe 2+ 1.1 0.8 1.0 L.I 0.6 t).5 1.5 1.3 0.3

47.3 i ~ .9 1.D7 i.(l()

17.6 :.t 2.08 ~.24 ~.1 5~ 0.16 ") 15 3.98 4.2" 8.67 4.63 2.6~ 2.40 v.25 = 20 0.31 <16 11.2o ~L2I 0.97 1189 (I.04 ,t 02 0.16 ,t 18 {).18 ~ 29

• : 0.()1 :L(II

98.53 '~'~.51)

I).3 "3 o

Sample: V83 V86 V85 V87a V88 V91 V92 V93 Date A.D.: 1861 1867 1867 1868 1871- 1872 1872 1881

1872

V95 V96 \ '~ : 1883- 1886 !~91 1906 :su4

Si02 47.9 47.9 47.4 48.0 47.4 47.5 47.0 48. 1 47.8 TiO2 1.00 1.00 1.04 0.99 1.07 t.04 1.03 0.93 1.01 A1203 17.3 16.9 18.2 17.7 18.4 16.3 18.4 18.0 16.3 F%O3 5.01 3.22 2.37 2.96 3.10 6.61 5.00 2.15 2,911 FeO 3.4 5.2 6.1 5.0 5.4 1.9 3.6 5.8 5.2 M n O 0.15 0.15 0.16 0.15 0.16 0.15 0.16 0.15 0.15 MgO 4.12 4.63 3.48 3.95 3.44 5.14 3.46 3.84 5.13 CaO 9.41 10.3 8.86 8.74 8.70 10.9 8.69 8.99 11.0 Na20 2.50 2.32 2.75 2.67 2.83 2.36 2.82 2.52 2.3i K20 7,26 6.75 7.28 7.74 7.50 6.29 7.44 7.53 6.43 H20 + 0.12 0.24 0.36 0.24 0.32 0.24 0.13 0.34 0.33 H20- 0.15 0.09 0.15 0.09 0.10 0.09 0.09 0.08 0.12 P205 0.88 0.88 0.84 0.87 0.86 0.84 0.85 0.93 0.83 CO, 0.03 0.02 0.02 0.03 0.02 0.07 0.02 0.01 0.02 F 0.22 0.27 0.25 0.23 0.16 0.20 0.22 0.14 0.10 C1 0.40 0.26 0.37 0.42 0.36 0.29 0.51 0.27 0.35 S <0.05 <0.01 <0,05 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01

47.~ t .0

1 7 4

4.1,~ 4.2 0.1> 4.08 t*.3O 2.5~ ".34 0,24 0~0~ ().9C~ {).02 {).26 0.4 ~

-* 0.01

9.92 : ?q.I)

Lt~5

~).15 3 78 '~.00 2.59 "53

0.32 ). ti)

~1,89

, ) ( ) I

-O=F,C1,S 0.20 0.17 0.20 11.19 1/.15 0.15 0.21 f).12 0. t6 I).22 ,~t ,

Total 99.65 99.96 99.43 99.59 99.67 99.77 99.21 99.66 99.91 99.92

Fe3+/Fe 2+ 1.3 0.6 0.3 0.5 0.5 3.1 1.2 0.3 0,5 0.9 ! ~

++,++

+ + ~0

.H

a 5

_ ,g

,0

b+

t-+

t-J +~

,+ +

'+c

o,x

+

+ ~

o'+

? D

O0

~O

00

0~

lJ

~+

lJ

~O

~

A

A

__

O0

00

OO

0~

lJ

~O

+~

O~

A

--

4u~

- =

;~ ~

~

'~

c :~

~

'~

~ i~

--

"=

~

b,

"~

D <

~<

~<

~<

"2

<

+,.-,

J

~

0

..,

b,

>0

2.

+ 5-

,

= .7_

+ ~.

:u.

• .C

=

,+ o

oc+

b,~

o,%

oo

,i

O0

00

00

0~

lJ

~O

~-

-~

--

~

A

A

~

_~

+~

+~

+~

+o+

~.~

.o

p !..

, .o

++

-. +o

p.

, +~

~

.--

.-u

A

A

:- .

..

..

..

,

r +

:I-

,~

~"

,+~

.L

. ::>

'- ~

C/:

-

+{

< < <

9

S=

S'-:

S <

D

H . E . B E L K I N F F A I .

Sample: V06T 1 V06T2 V44T3 V44T2 '~ 44T 1 Date A.D.: 1906 1906 1944 1944 . ~}44

SiO2 47.9 46.8 47.9 47.ta ~7.9 TiO2 1.0 t 0, 94 1.07 1.04 i .{} t AI20~ 15.2 16 5 10.2 " ~ 1 . . . . ~I F%O~ 3.46 4.96 3.39 4.03 4 21 FeO 4.6 2.9 4.4 3.9 ~ ( ,

M n O 0.14 (/.14 0.13 0.14 .~1 :, MgO 6.38 4.65 10.4 8.74 S.(I! CaO 12.3 9.73 18.7 16.2 ~ I Na20 2.14 2.51 1.08 1.44 ' 52 K20 5.72 6.96 2.49 3.73 4.45 H2 O+ 0.39 0.58 0.39 0.34 ' a 2" H 2 0 - 0.06 0.25 0.20 0.12 ,1,5~1 PeOs 0.84 0.82 0.51 0.61 !i,64 (702 0.01 < 0.01 0.02 0.01 t I} F 0.20 (I.25 0.08 0.12 ,~ 12 C1 0.73 R I 5 0.12 0.15 *~ 1~'. S <0.01 {).{}7 <0.01 <0.01 {} ;}i

-O = F,CI,S 0.25 ~. 17 0.06 0.0~ . ,.I},~

Total 100.83 98.04 101.02 100.68 ~, ~0.66

Fe 3+/Fe e ' 0.7 1.5 0.7 0 9 ,

50

40

10

CQ

¢0

1"0 /~ do 4b 50 aliquot A wt. %

280

FABLE 2

Analysis of A.D. 1631-1944 Vesuvius tephra ( values in wt.% }. See Table 1 for explanation

Fig. 2. Diagram comparing duplicate analyses of major elements (SiO2, TiO2, A1203, Fe203 t°t~, MgO, C aO, M n O , N a 2 0 , K 2 0 and P205) for five samples (V2, V73, V92, V132 , V 1 3 7 ) . The curve has a slope o f 1. The estimated uncertainties are approximately the size of the plotted points.

(Figs. 1A-D) on the 1:25,000 geologic base of Rosi et al. ( 1987 ). Appendix A summarizes the location and field notes. Obviously weathered or altered samples were avoided. The data reported here, except for three samples, were ob- tained from aliquots ground in tungsten car- bide at the University of Roma. Samples V44T1, V44T2, and V44T3 (Table 2) were ground in Reston using a jaw crusher with hardened Mn-steel plates and a grinder with alumina plates. No contamination (Thomp- son and Bankston, 1970) was detected tot the major elements reported here prepared by either method.

Duplicate splits of samples V2, V73. V92. V132, V137 were submitted at different times to assess major-element reproducibility. Fig- ure 2 shows that any instrumental, operator, or sample-preparation variations are well within the analytical uncertainties.

SAMPLING AND MAJOR-ELEMENT CHEMISTRY OF VESUVIUS ( A.D. 1631 - 1944 ) ~ 8 1

Chemical analyses

Major-element oxides (Si, A1, Fe t°ta~, Mg, Ca, Na, K, Ti, P, Mn) were determined in representative aliquots by wavelength-dispersive X- ray fluorescence spectrometry using the sioe method of Taggart et al. ( 1987 ). Total iron was TiOz determined as Fe203. The actual value of Fe203 AI20~

Fe203 was calculated after FeO determination (Ta- FeO bles 1 and 2). The technique used for FeO de- MnO termination was that of Peck (1964). CO2 was MgO

CaO determined coulometrically (Engleman et al., Na:O 1985). Total H20 was determined by Karl- K20 Fischer titration (Jackson et al., 1987). H20- H2 °+ was calculated by weight loss after heating at H~O-

P205 110~C for a min imum of one hour (Shapiro, co: 19751. H:O + is thus calculated from the dif- F ference between total H,O and H~O-. Sulfur cl was measured by the combus t ion / IR spectre, s- copy method of Kirschenbaum ( 1983 ). Fluo- FeO t°'a' rine and chlorine were determined by the selective-ion electrode method of Kirschenbaum ( 1988 ) and Aruscavage and Campbell ( 1983 ), respectively,

Results

One hundred and fifty-four samples ( 149 lavas. 5 tephra) were analyzed for the major elements, volatiles, and ferrous iron. Eighty-seven representative analyses of lava are given in Ta- ble 1 and five analyses of tephra are presented in Table 2. The complete data set of major, mi- nor. and trace-element chemistry can be ob- tained from the senior author or from Belkin et al. (1993). Representative portions of the rocks have been deposited at the Department of Mineral Sciences, Smithsonian Institution, Washington, DC and at the Dipart imento di Geofisica e Vulcanologia, UniversitY. di Na- poli "Federico II".

Variation of major elements

The recent Vesuvius lavas are remarkably invariant with respect SiO2, FeO t°ta~, TiO2,

FABLE 3

Mean, l a standard deviation, and the range (wt.%t of 149 recent (A.D. 1631-1944 ) Vesuvius lavas

Mean I a Range

Fe 3+/Fe e+

48.0 0.36 47.0-49.3 0.98 0.06 0.71- 1.~)8

17.4 1.12 13.3-19.,~ 3.67 1.25 0.93- 8.08 4.4 I. I 5 0.64- 6.8 0.15 0.01 0 .13-0.16 4.31 0.98 1.96- 7 66 9.58 l 19 7.17-13 30 2.44 0 28 1.63- 3 ~1 7.16 0.68 4.79- 8.56 0.33 0.12 0.03- 0 ~;1 0.17 0.14 0 . 0 - 0 . 6 3 0.87 IJ 0~ 0.40- 1 ,11 0.02 Od)2 0.0 - 0.. 3 0.211 0.04 0.08- 0. ~3 0.32 0.12 0.(/4- 0 (~ 1

>/0.01

7.8 0.2~ 6.5- 8.3,~

1.0 1.23 0.12-11.4

MnO, and P205 (Table 3 and Fig. 3a,b). The narrow range of silica content suggests that the crystallizing phases have approximately the same silica content as their parental liquid. Modal analysis on about 80 lavas is reported by Trigila and De Benedetti (1993-this volume) . Leucite ( m e a n = 2 6 vol.%; range= 2-45 vol.%) and clinopyroxene ( m e a n = 9 vol.%; r a n g e = l - 2 4 vol.%) are the predominant phenocrysts. Plagioclase ( m e a n = 3 vol.%; range=0-13 vol.%) is a minor phenocryst phase and olivine, biotite, opaques and apatite are uncommon phases (usually < 1%). Mi- crophenocrysts are common in the microcrys- talline groundmass and for some phases, e.g., leucite, a size cont inuum exists between phenocryst and microphenocryst.

A suitable parameter to study elemental variation in these rocks is MgO (Fig. 3a,b). The covariations of CaO, A1203, and K20 with respect to MgO are uncommonly linear with high correlation coefficients (A1203: r 2 = 0.99, CaO: r 2 =0.95, K20: r 2 =0.92 ).

282 H.E. BELKIN El AL

(a) FeO total

, # ' - , . . : - . . - .

2 3 4 5 6 7 8

2 2

20 t m

la AI203

16 t m m 14-

12

10

8

4

56

54

52

50

4 8 '

46

TiO 2

9 10 I1

m

SiO 2

o 4

o2 nl

I

~4]I - -

[J 6]

O2 1

20-

18-

16-

,4-

12-

'i! !

MnO

m

P205

CaO

(b)

~ 0 m

J 24

4 N ~ O

I m

'- | D a m i ", ...... ~_j 9 lc ~(

~ m ~ i l

m m m

!

11

m m D

B mlm mmm m

| m ram| m

2 a 4 s e z a a 10 11 fi i 5 6 ~ a MgO ~ ' % MgO wt%

9 10, ! 1

Fig. 3a,b. Variation diagrams o f the major e l ements (wt.%) plotted as a function of MgO content. 'The three A.[). 1944 tephra samples are the most MgO-rich and are de l ineated in the diagram SiO2 versus MgO. The two 1906 tephra samples. MGO=6.38 (V06T1) and 4.65 (V06T2) are not marked.

Major-element variation as a function of time of eruption

Am6 et al. (1987) has divided the recent eruptive history of Vesuvius into 18 cycles on

the basis of detailed historical records. A quiescent period of no longer than 7 years pre- cedes eruption and the climax or final eruption of each cycle is a fairly vigorous eruption. Fig- ure 4 shows the Arn6 cycles. We find no major-

S A M P L I N G A N D M A J O R - E L E M E N T C H E M I S T R Y O F V E S U V I U S ,

2[' C a O

I l(,t •

ARN0 CYCLES 12 1415 16 34 7 8 ,13 17

_ 1 [ _

1(, K~O

• i i . . . . . • i, t

, , k it i

A.D, 1 6 3 1 - 1 9 4 4 )

24 [ , A I 2 0 3

t--

e ~

1:,[ MgO •

I I ~ [

i • "ll i I

i

,};

50- S i O 2

4tl

48; i

47

46 I I 1600 1650 1700 1750 1800 1850 qgoo 1950

DATE A.B.

Fig. 4. Variation (wt.%) of selected major elements as a function of the date of eruption. The A.D. 1631 eruption and eighteen Arn6 cycles are indicated.

283

element variation with regard to these cycles. Lava flow heterogeneity, characterized mainly by different proportions of leucite and clinopyroxene phenocrysts (Trigila and De Bene- detti, 1993-this volume) produce chemical differences in any one eruption that are similar to the entire range of lava chemistry.

The A.D. 1631 lava samples cannot be distinguished from subsequent lavas by their major-element chemistry. They are also highly porphyritic, contain a mineral assemblage similar to subsequent lavas (Trigila and De Benedetti, 1993-this volume), and their compositional variability is controlled to the same degree by varying amounts of clinopyroxene phenocrysts.

Nomenclature

Joron et al. (1987) comment that the nomenclature of the potassic rocks of the entire Roman Comagmatic Province is an uncertain and debatable problem. Various schemes are current in the literature for the classification of volcanic rocks (Le Maitre et al., 1989: Middle- most, 1975).

Le Bas et al., ( 1986 ) refined a volcanic classification scheme based on total alkalis versus silica (TAS) diagram. Figure 5 shows that most

15-

0

+ 0

13

I I tephrtphonoltte fotdlte 11 ,

: . l p S p o h ~ b a s a l t , c t r achyand es,tr ~

i 9t

7i tephrt te a m " trachy ~ ! andeslte

! L t[achybasa R 5 '

3! , i basaltic andeslte

basalt

37 41 45 49 53 57 S102 wt%

61

Fig. 5. A portion (37-61 wt.% SIC2) of the total alkalis versus silica volcanic rock classification diagram of ke Bas et al. (1986). One hundred and fifty-four analyses are plotted: the 1944 tephra samples are denoted with an × .

284 H,E. BELKIN ET A t .

• • . ~ high-K series . . .

nqk • ..--"

0 m I l l • . . , . . , -

4. . . , ' "

÷ j ,"

2 2 3 4 5

Na20 wt%

Fig. 6. One hundred and forty-nine lavas and five tephra samples (1944 tephra plotted as + ) as plotted as K20 versus Na20 (wt.%). All compositions with a K20/Na20 ratio greater than the dashed line belong to the high-K series of Middlemost ( 1975 ). The curves K20/Na20 equal to 1.0 and 1.5 are also shown.

45~

40 ~

35~

3o~

u >" 254 c

20~

~54

[

sl

o3i [FeO i

O* 1 cj 1 2 3 4 5 6 7 8

weight percel~!

Fig. 7. Histogram of FeO and Fe203 in the lavas and tephra as a function of weight percent. The arrows indicate the mean (A = FezO3; B = FeO) composition of clinopyroxene phenocrysts reported by Rahman ( 1975 ) for lavas erupted in the period from A.D. 1631-1944.

samples are phonotephrites. Phenocryst variation, clinopyroxene accumulation or depletion, produces uncommon compositions such as tephriphonolite, trachybasalt, tephrite, and basalt.

Middlemost ( 1975 ) has used the K20/Na20 ratio as a criterion to distinguish various potassium-rich rocks. Figure 6 indicates that all

8

74

6

5

4-

3

2"

1-'

o

~. • Fe203 wt.%

•

- .

• n •

r •

u

MgO wt%

Fig. 8. Covariation diagram of Fe203 and Mg(~ (wt.%) for one hundred and forty-nine lavas and five tephra samples.

0.2- C 0 2 w t . %

i • A 0,1

• ,,Ik A

i 2 3 4 s 6 -~ 8 Fe203 wt.%

Fig. 9. Covariation diagram of CO2 and FezO3 (wt,%) lbi one hundred and forty-nine lavas and five tephra samples.

the Vesuvius samples (KzO/Na20> 1.5) belong to the high-potassium series of Middle- most (1975).

Fe3+ /Fe 2+ ratio of the lavas and tephra

The Vesuvius lavas erupted during the 300 year recent activity are relatively oxidized (average Fe 3 +/Fe 2 + = 1.0 ). The histograms (Fig. 7 ) for bulk rock Fe203 and FeO show skewed distributions. The skewed distributions are similar but opposite because the total iron content (Fig. 3a) is relatively unvarying. The modes of the FeO and F e 2 0 3 values are coin- cident with the values determined by Rahman (1975) for clinopyroxene phenocrysts. This suggests that the parental composition had a ferric/ferrous ratio of approximately 1.0. High Fe203 values, greater than approximately 5 wt.%, tend to correlate with lavas with a red-

S A M P L I N G A N D M A J O R - E L E M E N T C H E M I S T R Y O F V E S U V I U S ( A . D . 1 6 3 1 - 1 9 4 4 ) 2 8 5

dish-brown tinge in contrast to the grey or dark grey color of the average lava. These oxidized lavas result from local effects in the upper parts of the Vesuvius magma chamber just prior to eruption or from the eruptive process such as pervasive gas alteration or the intimate incor- poration of an oxidized crust in the lavas. These typically include samples located near or

28

24

CaO

2O

4

~t.c 20

OLc ]6

uJ ¢.A 12 ¢1:

t.9 8 i

~ O- Cpx

I . . . . . . . . . . . .

K20

I I I I I , ~ x i

v

3t PI AI203

25.

OLc

~5

lO

I [ J _ l I Oq 2 4 6 8 10

MgO

OCpx

12 14 16 ' 8

on the rim of the crater (e.g., V 148 ); although, lavas with elevated Fe203 values occur at all positions along a flow. Also elevated Fe~O3 values cannot be related to any variation in major-elemental composition, e.g., MgO (Fig. 8). This connection with local alteration is supported by the fact that, in general, highly oxidized lavas show elevations in CO2 (Fig. 9 ); however, there is no correlation of Fe203 with the volatiles F or CI (Table 1 ).

Discussion

The porphyritic character of the A.D. 1631- 1944 lavas contrasts with the nearly aphyric nature of the pre-79 A.D. plinian products; the total volume erupted between 1631 and 1944 is of the order of 0.5-1.0 km 3, comparable to larger plinian events. Together, these two ob- servations suggest that, while a common res- ervoir has influenced all the Somma-Vesuvius activity (i.e., less than about 30,000 y.B.P.), producing comparable volumes for active epi- sodes, the manner of magma crystallization during storage and escape is completely different.

The A.D. 1631-1944 lavas, averaging 40% phenocrysts, provide poor candidates for parental magmas. Lavas with relatively low

Fig. 10. Variation diagrams for CaO, K20, and A1203 versus MgO. The solid lines from 2 to 10.5 wt.% MgO are the linear regression trends of the bulk-rock chemistry from the complete data set (Fig. 3). The dots represent mean values for phenocryst compositions for lavas of the ~.D. 1631-1944 period. The leucite (Lc) composition is relatively constant (Deer et al., 1963; Joron et al., 1987 ). The plagioclase (Pl) varies (Joron et al., 1987) with respect to A1203 (30-34 wt.%) and CaO ( l 4-18 wt.%) and these variations are indicated by a solid line. The clinopyroxene (Cpx) composition is the mean taken from the study by Rahman ( 1975 ) and the size of the dot represents the compositional range. The boxes shown in the A1203 and CaO diagrams and the solid line in the K20 diagram are the clinopyroxene composition ranges reported by Joron et al. (1987). The solid triangles represent residual compositions from the extraction of modal phenocryst clinopyroxene (converted to wt.%) of the composition reported by Rahman ( 1975 ).

286 H.E. BELKtN ET AL.

amounts of phenocrysts, (e.g., V6=13%; V43 = 10%)yield compositions (Table 1 )near the mean of the 149 lava analyses. However, this approach is flawed. The phenocrysts are large enough and/or so unevenly distributed that modal analysis (Trigila and De Benedetti, 1993-this volume) on orthogonal thin sections (V128) produced a two to three-fold differ- ence in the clinopyroxene value.

The exceptional linear correlation of A1203, CaO, and K20 with respect to MgO (Fig. 3a,b) suggests that the entire range of lava compositional differences are controlled phenocryst proportions. The obvious abundance of clinopyroxene and leucite phenocrysts suggests that these phases may provide the necessary vari- ance in composition.

Figure 10 shows the covariance of CaO, A1203, and K20 versus MgO. The entire data set, lavas and tephra, have been regressed and the trend line is shown. Three phenocryst compositions, leucite, plagioclase and clinopyroxene, are plotted. Leucite is essentially stoichi- ometric, plagioclase has small variations from an average of ~ An8o, and the clinopyroxene shows the greatest variability in composition (Joron et al., 1987). Nevertheless, the bulk- rock trend lines clearly show that the total lava compositional diversity is caused by clinopyroxene phenocryst redistribution, either a relative accumulation or depletion (Fig. 10 - - CaO vs. MgO ). A subset of lava compositions for which modal analysis was performed (Tri- gila and De Benedetti, 1993-this volume) and that contained only leucite and clinopyroxene phenocrysts were selected. The plotted values (Fig. 10; filled triangles) represent the residual after subtraction of the clinopyroxene phenocrysts. Their coincidence with the bulk composition trend line supports the clinopyroxene control. There is no clear evidence that leucite, either removal or accumulation, has directly controlled lava composition variability. However, there is reasonably an inverse re- lationship between the leucite and clinopyrox-

ene phenocrysts considering volume; the more clinopyroxene phenocrysts the potentially fewer leucite phenocrysts. The covariance of A1203 versus MgO (Fig. 3a) is exceedingly good. This is because the leucite, clinopyroxene, and presumed parental magma compositions are roughly colinear in A1203/Mg O space.

Conclusions

Assessment of the major-element chemistry data reveals that Vesuvius erupted a relatively homogeneous product from A.D. 1631-1944. The major-element variation is the result of the distribution of the clinopyroxene phenocrysts. The major-element chemistry cannot distinguish between the A.D. 1631 lavas and subsequent eruptions.

This extensive sampling and analytical pro- gram should provide a unified database as a starting point for future studies of the A.D 1631 - 1944 Vesuvius activity.

Acknowledgements

This project has been undertaken as part of a bilateral U.S. Geological Survey-Italy agree- ment. We greatly appreciate the high-quality analytical work of J.S. Mee, D.F. Siems, JoE. Taggart, A.J. Bartel, J.R. Gillison, C.J. Skeen, H. Smith, C.L. Prosser, M.G. Kavulak, W.B. Crandell from the Branch of Geochemistry, U.S. Geological Survey. We thank Maura Ho- gan, Graphics specialist U.S. Geological Sur- vey, for the sample location maps. We grate- fully appreciate the thoughtful and constructive reviews ofG. Fitton, R.T. Helz, R.P. Koeppen. and R. Macdonald.

References

Arn6, V., Principe, C., Rosi, M., Santacroce, R., Sbrana, A. and Sheridan, M.F., 1987. Eruptive histoD. In: R.

SAMPLING AND MAJOR-ELEMENT CHEMISTRY OF VESUVIUS (A.D. 1631 - 1944 ) 287

Santacroce (Editor), Somma-Vesuvius. CNR Quad. "La Ricerca Scientifica", 8:114: 53-103.

Aruscavage, P.J. and Campbell, E.Y., 1983. An ion selective electrode method for the determination of chlorine in geologic materials. Talanta, 30: 745-749.

Barberi, F., Bizouard, H., Clocchiatti, R., Metrich, N., Santacroce, R. and Sbrana, A., 1981. The Somma-Ve- suvius magma chamber: a petrological and volcanol- ogical approach. Bull. Volcanol., 44:295-315.

Belkin, H.E., Kilburn, C.R.J., De Vivo, B. and Trigila, R., 1991. Sampling and analytical chemistry of the recent Vesuvius activity (A.D. 1631-1944). Int. Conf. Ac- tive Volcanoes and Risk Mitigation, Abstracts, 27 Aug.- 1 Sept. 1991, Napoli, Italy.

Belkin, H.E., Kilburn, C.R.J. and De Vivo, B., 19'93. Chemistry of the lavas and tephra from the recent (~,.D. 1631-1944) Vesuvius (Italy) activity. U.S. Geol. Surv., Open-File Rep. 93-399, 44 pp.

Deer, W.A., Howie, R.A. and Zussman, J., 1963. Rock Forming Minerals Vol. 4, Framework Silicates. Loag- roans, Green, and Co., London, 435 pp.

Engleman, E.E., Jackson, L.L. and Norton, D.R., 1985. Determination of carbonate carbon in geological materials by coulometric titration. Chem. Geol., 53:125- 128.

Jackson, L.L., Brown, F.W. and Neil, S.T., 1987. Major and minor elements requiring individual determination, classical whole rock analysis, and rapid rock analysis. In: P.A. Baedecker (Editor), Methods for Geo- chemical Analysis. U.S. Geol. Surv., Bull., 1770: G1- G23.

Johnston-Laves, H.J., 1884. The geology of Monte Somma and Vesuvius, being a study in volcanology. Geol. Soc. London Quart. J., 40:35-119.

Joron. J.L., Metrich, N., Rosi, M., Santacroce, R. and Sbrana, A., 1987. Chemistry and petrography. In: R. Santacroce (Editor), Somma-Vesuvius. CNR Quad. "La Ricerca Scientifica", 8, 114: 105-174.

Kirschenbaum, H., 1983. The classical chemical analysis of rocks - - the old and the new. U.S. Geol. Surv., Bull. 1547, 55 pp.

Kirschenbaum, H., 1988. The determination of fluoride in silicate rocks by ion selective electrode: an update. I.J.S. Geol. Surv., Open-file Rep. 88-588, 5 pp.

Le Bas, M.J., Le Maitre, R.W., Streckeisen, A. and Zanet- tin. B., 1986. A chemical classification of volcanic rocks based on the total alkali-silica diagram. J. Petrol., 27: 745-750.

Le Maitre, R.W. (Editor), 1989. A Classification of Ig- neous Rocks and Glossary of Terms. Blackwell, Ox- ford, 193 pp.

Middlemost, E.A.K., 1975. The basalt clan. Earth-Sci. Rev., 11: 337-364.

Peck, L.C., 1964. Systematic analysis of silicates. U.S. Geol. Surv., Bull. 1170, 89 pp.

Rahman, S., 1975. Some aluminous clinopyroxenes fi'om

Vesuvius and Monte Somma, Italy. Mineral. Mag.. 40: 43-52.

Rolandi, G., Barrella, A.M. and Borrelli, A., 1993. The 1631 eruption of Vesuvius. J. Volcanol. Geotherm. Res., 58: 183-201.

Rosi, M., Santacroce, R. and Sbrana, A.. 1987. Geological map (1:25000) of Somma-Vesuvius volcanic com- plex. In: R. Santacroce (Editor), Somma-Vesuvius. CNR Quad. "'La Ricerca Scientifica", vol. 8, 114:

Rosi, M., Principe, C. and Vecci, R., 1993. The 1631 Ve- suvius eruption: a reconstruction based on historical and stratigraphical data. J. Volcanol. Geotherm. Res., 58: 151-182.

Santacroce, R. (Editor), 1987. Somma-Vesuvius. ( 'NR Quad. "La Ricerca Scientifica", vol. 8, 114:1-25 I.

Shapiro, L., 1975. Rapid analysis of silicate, carbonate, and phosphate rocks - - revised edition. U.S. Geol. Surv., Bull. 1401, 76 pp.

Taggart, J.E., Lindsey, J.R., Scott, B.A., Vivit, D.V.. Bar- tell, A.J. and Stewart, K.C., 1987. Analysis of geologic materials by wavelength dispersive X-ray fluorescence spectrometry. In: P.A. Baedecker (Editor), Methods for Geochemical Analysis. U.S. Geol. Surv., Bull., ! 770: El-E19.

Thompson, G. and Bankston, D.C., 1970. Sample contamination from grinding and sieving determined by emission spectrometry. Appl. Spectrom., 24:211-219.

Trigila, R. and De Benedetti, A., 1993. Petrography of the A.D. 1631-1944 recent Vesuvius activity. J. Volcanol. Geotherm. Res., 58:315-343.

Vaggelli, G., Belkin, H.E., De Vivo, B. and Trigila, R., 1992. Silicate-melt inclusions in recent Vesuvius lavas (A. D. 1631 - 1944 ): I. Petrography and microthermo- merry. Eur. J. Mineral., 4:1113-1124.

Vaggelli, G., De Vivo, B., and Trigila, R., 1993. Silicate- melt inclusions in recent Vesuvius lavas ( 1631-1944): II analytical chemistry. J. Volcanol. Geotherm. Res., 58: 367-376.

Villemant, B., Trigila, R. and De Vivo, B., 1993. Geo- chemistry of Vesuvius during 1631-1944 period. J. Volcanol. Geotherm. Res., 58: 291-313.

Washington, H.S., 1906. The Roman Comagmatic Re- gion. Carnegie Inst. Washington, Publ. 57, 199 pp.

Appendix A

List of the samples of A.D. 1631-1944 Vesuvius recent products (collected in 1988 by CRJK). Samples located using the 1:25000 geological map of Somma-Vesuvio by Rosi et al., 1987. Where appropriate, locations are given as direction and distance from the center of the Gran Cono (GC L the central cone of Vesuvius. Abbreviations: TA = Torre Annunziata; TG = Torre del Greco: M = Samples cut by "marble" cutter, not in Dipartimento di Geofisica e Vulcanologia; SUM = summit

288

TABLE A 1

Lava samples

Sample Full reference Location no .

Vl V/1631/2TA

72 7 /1631/3TA 73 V/1631/4TA 74 V/1631/3TG 75 7 / 1 6 3 1 / 4 T G V6 V/1631/5

V7 V/1631/7 V8 V/1694/1

V9 V/1694/2 V10 V/1694/3 V l l V/1697/1

Vl2 V/1697/1M V13 V/1697/2 V14 V/1697/2M 715 7 /1697 /3M

V16 7 / 1 7 1 4 / I M 717 7 /1714 /2

718 V/1717/1M 719 7 /1717 /2M V20 7/1723/1

721 V/1737/1

V22 V/1737/2 723 7 /1737 /3 724 7 /1737 /4 V25 V/1751/1

V26 V/1751/2 727 7 /1751 /3 V28 V/1754/1 V29 V/1754/3 730 7 /1754 /4

V31 V/1760/1

V32 V/1760/2M V32a V/1760/2M

733 7 /1760 /3 734 7 /1760 /4 735 7 /1760 /5M V36 V/1760/6 V37 V/1760/7

Torre Annunziata; Lido, NR Terme Vesuviane as V1 as V1 Torre del Greco; FS Stazione as V4 Torte Annunziata; Stazione Sta Maria la Bruna as V6 5 km W GC; 750 m ESE Cim. di Resina. as V8 as V8 Torre del Greco; Campo Sportivo; 4.25 km SW GC a s V l l as V l l a s V l l Torre del Greco; NE of Auto- strada; 5 km SE GC Boscotrecase Road; 5 km SSE GC SSW Massa del Carceriere; 3.75 km SE GC Cappella Nuova; 4.2 km S GC as V18 Terzigno; Campo Sportivo: 3.7 km ENE GC [Note: what is mapped as a 1723 dagala maybe 1906 material] 200 m N Casa Serpe; 3.25 km SW GC as V21 Fosso Bianco; 2.75 km SW GC as V23 Boscoreale; Villa Massa; 6.4 km SE GC as V25 as V25 N branch; 3.8 km SE GC N branch; 5.3 km SE GC S branch; Boscoreale (Balzani): 4.8 km SE GC Torre Annunziata; C. Ranieri; 7 km S G C as V31 as V31; thin section only

as V31 W of Berardinelli; 5. I km S GC as V34 100 m S of vent area; 4.1 km S GC as V36

H.E. BELKIN E l AL.

Sample Full reference Location 130.

V38

V39

V40 V41 742

V43

V44

V45 V45a

V46

V47

V49

V50 V5I 752

V53

V54

V55 756

V57 V58 V59 V60 V61

V62 V63 764 V65 V66 767 768 V69 V70

V71 V72 773

V/1760/8 E of Massa S. Giorgio; 4.9 km S GC

V/1767/1 toe of flow; N ofCim, di Port~ci: 5.5 km WSW GC

V/1767/2 N of San Vito; 4.3 km WNW GC V/1767/3 asV40 V/1761-71/1 Torre del Greco; 3.25 km WSW

GC V/1761-71/3MTorre del Greco; facing Casa

Rossa; 3.5 km WSW GC V/1794/2 Torte del Greco; lowest vent area;

3 km SW GC V/1794/3 asV44 V/1794/4 Torre del Greco; Port; 6.5 km SE

GC ( 100 m NW V46 ): thin section only

V/1794/6 Torre del Greco; Port; 6.5 km SW GC

V/1794/7 Torre del Greco; SE margin of flow; 6.3 km SW GC

V/1805/1 S branch; 750 M NE Camaldoli, SE ofC. Luciniello: 4.5 km SSW GC

V/1805/2 asV49 V/1805/3 as 749 V/1805/4 middle branch; near Villa Cervaslo

4.5 km SSW GC V/1806/1 S branch; 750 m E of Camaldoh:

4.7 km SSW GC V/1806/2 S branch; 375 m N Cappella

Nuova; 4 km SSW GC V/1806/3 asV54 V/1806/4 N branch; 375 m NE Lamana; 5

km SW GC V/1806/5 as V56 V/1822/1 forestale; 2 km S GC V/1822/3 forestale; 2.1 km S GC V/1822/4 forestale; 2.6 km S GC V/1834/2M quarry 600 m NW Boccia al

Mauro; 6.3 km ESE GC V/1834/3 asV61 V/1834/6 asV61 V/1834/8 WSW of Terzigno; 3.1 km SE GC V/1839/1M S of Terzigno; 5.7 km ESE G ( V/1839/2 S of Terzigno; 5.1 km ESE GC V/1839/3 asV66 V/1847 / l a forestale; 1.9 km SW GC V/1847/2M forestale; 2.1 km SE GC V/1850/1 W margin of exposure; 1.9 km SSE

GC V/1850/2 2 km SSE GC V/1850/3 2.1 km SSE GC 7/1855/1 N branch; S. Sebastiano (dagala):

5.9 km WNW GC

SAMPLING AND MAJOR-ELEMENT CHEMISTRY OF VESUVIUS (A.D. 1631-1944 ) 289

Sample Full reference Locat ion no.

Sample Full reference Locat ion no.

V74 V75

V76 V76a V77 V78 V79

V80

V81 V82

V83

V84

V85

V86 V87

V87a V88

vg0 Vgl

V92

V92a

V93

V93g

V94 V95

V96 V97

V98

V99 v100 Vl01

v102

v104 v105

V/1855 /1M V/1855 /2

V/1855 /3M V/1855 /3M V/1855 /4 V/1858/1 V/1858 /2

V/1858 /3

V /1858 /4M V/1858/5

V/1861 /2

V/1861 /3

V/1867/1

V/1867 /2 V/1868/1

V/1868 /2 V/1871-72 /1

V/1872 /2a V/1872 /2

V/1872 /3

V/1872 /4

V/1881/1

V / 1 8 8 1 / l

V /1881 /2 V/1883-1906 / 1 7 / 1 8 8 6 / 1 V/1891-94 /1

as V73 N branch, W toe; S. Sebastlano; 6.75 km WNW GC as V75 as V75; thin section only as V75 forestale; 1.3 km W GC N side of road to Ercolano: 4 km WNW GC E side of road to Ercolano; 3.5 km W GC as V80 N side of road to Ercolano; 3 km WNW GC Torre del Greco, Hospital; 4 km SW GC Torre del Greco; toe of flow: 4.75 km SW GC forestale; 1.5 km S Colli Umberm', 1.3 km SE GC as V85 quarry face N of Stazione lnferiore della Funivia; two thin sections; covered by 1872 lava: 4 km ENE C as V87 toe of flow; NW ofC. Cerasiello; 3,7 km WSW GC forestale; 1.8 km SW GC N branch; S. Sebastiano; 5.5 km WNW GC S branch; S. Sebastiano; 4 km WNW GC above S. Sebastiano; 2.75 km WNW GC; thin section only tumulus on ESE flank of GC ("750 m ESE GC" ) glassy sample, thin section only; as V93 as V93 Cognoletta; 2 km SE GC

forestale; 2 km SW GC between C. Margherita and Um- berto; 1 km NNW GC

V/1891-94/2Mbetween C. Margherita and Um- berto; 1 km NW GC

V/1895-99 /1 V / 1 8 9 5 / 9 9 / 2 V / 1 8 9 5 - 9 9 / 3

V / 1 8 9 5 - 9 9 / 4

V/1906 /3 V /1906 /3M

forestale; 1.9 km WNW GC as V99 E side of Colli Umberto; 1.25 km NW GC NW side of Colli Umberto; 1.75 km NW GC as V105 N Boscotrecase; middle branch, E limb; 6.3 km SSE GC

N Boscotrecase: middle branch, W limb; 4.6 km SSE GC W branch: E ofC. Aniello: 4 km SSE GC asV107 as V108; thin section only as V108; thin section only within Somma Caldera: Piazzale; 1.3 km SE GC as VI09 Valle dell'Inferno; 1.6 km E GC Valle dell'Inferno: 1.6 km ESE GC S branch: NE of Terrioni: 3.6 km SE GC N branch; Terzigno, S side of road to Campo Sportivo: 4.4 km ESE GC a s V l l 4 N branch; Terzigno, S side of road Sportivo (NW): 3.6 km ESE GC N branch, S margin: 3.3 km ESE GC a s V l l 7 S branch: S of Buscodi Cupaccia; 2.8 km SE GC hornitoes; 1.55 km SE GC hornitoes; 1.5 km SE GC Main (S. Sebastiano) flow; 2.25 km NW GC asV122 asV122 as V122 as V122 main flow: by road: 2.5 km NW GC main flow: Colle Margherita; 1.25 km NNE GC: 3 octhogonal thin sections as V128 asV128 asV128 main flow; tumulus, Atrio del Cav- allo; 1.1 km NNE GC main flow, W margin; 1 km N GC main flow, N branch, N side; 4.4 km NW GC as V 134; 2 thin sections as V 13 4; thin section only main flow, N branch; S side opposite V134:4.4 km NW GC; thin section only

V106 V/1906/4B

V107 V/1906/TM

V108 V/1906 /SM V |08a V/1906 /8M V108b V/1906 /8M V109 V/1906 /10

V I I 0 V/1906 /12M V l l l V /1913-44 /1 Vl12 V / 1 9 1 3 / 4 4 / 2 V l l 3 V/1929 /1M

Vl14 V/1929 /3

Vl15 V/1929/3 Vl16 V/1929 /4

V117 V/1929/5

Vl18 V/1929 /6M Vl19 V/1929 /7M

V120 V/1941-42 /1 V121 V/1941-42 /1 V122 V / 1 9 4 4 / 1 / ?

V123 V / 1 9 4 4 / I / l a V124 V / 1 9 4 4 / l / l a V125 V / 1 9 4 4 / 1 / l b V126 V / 1 9 4 4 / 1 / l c V127 V / 1 9 4 4 / 1 / l d

V128 V / 1 9 4 4 / l / 2 a

V129 V / 1 9 4 4 / l / 2 b VI30 V / 1 9 4 4 / 1 / 2 c V131 V / 1 9 4 4 / l / 2 d V132 V/1944/l/3

V133 V / 1 9 4 4 / 1 / 4 V134 V / 1 9 4 4 / [ a / l

Vl35 V / 1 9 4 4 / l a / 2 V135a V / 1 9 4 4 / [ a / 3 V135b V / 1 9 4 4 / [ a / 4

V136 V / 1 9 4 4 / I a / 6 M N side of 1872 dagala; 3.5 km NW GC

V136a V / 1 9 4 4 / l a / 6 as V136; thin section only V136b V / 1 9 4 4 / l a / 5 as V136; thin section only

290

Sample Full reference Locat ion n o .

V137

Vt38

V138a V139

V139a

V140

V141

V142 V142a V143

V143

V144 V145 V145a V146

V147 V148

V149

V / 1 9 4 4 / l a / 7 main flow, N branch, N limb: S. Sebastiano; 5.5 km NW GC

V/1944 / I b / 1 M main flow, S branch: S of 1872 dagala; 3 km NW GC

v / 1 9 4 4 / l b / l as V138: thin section only V / 1 9 4 4 / l b / 2 M main flow, S branch; S of 1872 da-

gala; 3.2 km NW GC V / 1 9 4 4 / l b / 2

V/1944 /2a

V/1944/3a

V / 1 9 4 4 / 4 / l a V / 1 9 4 4 / 4 / 1 b V/1944 /5 /1

V / 1 9 4 4 / 5 / 3

V / 1 9 4 4 / 5 / 2 V / 1 9 4 4 / 6 / l p 7 / 1 9 4 4 / 6 / 1 V / 1 9 4 4 / 6 / 2

V / 1 9 4 4 / 6 / 3 V / 1 9 4 4 / S U M / 1 V / 1 9 4 4 / S U M /

as V139; thin section only Colle Margherita; toe of flow, t km NW GC Colle Margherita: toe of flow: 1.2 km NW GC. forestale; 1.4 km W GC as V 142; thin section onb forestale: toe of N tongue: 1.5 km SE GC forestale: as V 143; thin section only forestale; 1.4 km SE GC forestale; 1.55 km S GC as V145; thin section only forestale; toe of eastern tongue: 1.9 km S GC forestale; W margin: 1.6 km S GC S rim of GC

SW rim of GC

H.E. BELKIN k'l A!

Sample Full reference Locat ion n o

V149a V / 1 9 4 4 / S U M / NNWflankGC. c losetorm~. thl r 3 section onb

V150 V/1906/13 N branch, near toe; Molara. ~ l km SE GC

~,151 V/1906/14 as V150 VI54 V / 1 9 0 6 / t 7 asV155 V 155 V/1906/18 middle branch, Shmb: S Bosco-

trecase, Circumvesuviana Ra~l- way: 6.75 km SSE GC

V 156 7 / 1 9 4 4 / D 1 toe of debris flow; by road, ' km NNW G C thin section onb

l-ephra samples

Sample Location rio.

V44T1 V44T2 V44T3 V06T1

V06T2

1944; 1.1 km NNE GC 1944; 1.1 km NNE GC 1944; rim of Somma Caldera: 1.75 km S I c t ,~ 1906: from collection ofDipart . Geofisica c Vul- canologia, Napoli, location unknown 1906; from collection ofDipart . Geofisica c Vui. canologia, Napoli, location unknown

Documents

Sampling and major element chemistry of the recent (A.D. 1631-1944 ) Vesuvius activity