IN PETR
GE
CHEM
ROGENES
FE
F
EOLOGIC
DIPONE
MICAL AN
SIS STUDY
PUBL
EBRIYAN
FACULT
CAL ENG
EGORO U
ND PETRO
Y OF MUR
LICATIO
N KUSUM
L2L005
TY OF EN
GINEERI
SEMARA
JULY 2
UNIVERS
OGRAPHY
RIA VOLC
ON DRAF
MA PRAS
5817
NGINEER
ING STU
ANG
2010
SITY
ANALYSI
ANO, CEN
FT
SETYA
RING
UDY PRO
IS
NTRAL JA
1
Chemical and Petrography Analysis in Petrogenesis Study of Muria Volcano, Central Java
By:
Febriyan Kusuma Prasetya*, Hadi Nugroho* and Prakosa Rachwibowo* (corresponding email: ryan_mobilesuit@yahoo.co.uk)
*Geological Engineering Study Program, Faculty of Engineering, Diponegoro University, Semarang, Indonesia
ABSTRACT
Muria volcano is located in the north coast of Central Java, in a northward extending land known as Muria Peninsula. Muria volcano has long been known as an anomaly of volcanoes in Java due to its different features, most conspicuous viewed from its position, compared to the other volcanoes, which is not located in regular pattern of Java’s volcanic arc.
Purposes of this research are identifying characteristic of Muria magma, finding out relationships between characteristic of Muria erupted lavas which is expressed in mineralogy and geochemical to its tectonic setting, the last is proposing petrogenesis of Muria volcano. Methods used in this research are survey method, descriptive method, and laboratory method. Extended by analytical method include petrography analysis and chemical analysis. K-Ware Magma software is used in helping these analyses.
Igneous rocks from Muria volcano have intermediate to ultrabasic character regarding to its silica abundances with molecule weight percentage of SiO2 = 44.25 to 55.42. Respects to silica saturation, these rocks are ranged from silica saturated which consists only saturated minerals, to silica undersaturated which essentially contains minerals such as olivine and feldspathoids i.e.: leucite and nepheline. Magma series of Muria volcano fall into the alkaline magma series shown by molecule weight percentage of Na2O + K2O = 9.24 to 10.1, then its subdivision is ranging from K-series to high-K series. Muria volcano is a typical of transitional volcanism between island arc and intra-continental plate environment regarding to its tectonic setting. Enrichment of lithophile elements (LILE) along with niobium anomaly in spiderdiagram marks an involvement of subduction zone fluid added to the mantle source of magma during partial melting. However, niobium anomaly still is not showing real depletion of niobium whereas it is truly has been slightly enriched from mid-ocean ridge basalt (MORB) value. Slight enrichment of the other high field strength elements (HFSE) marks the existence of magma source rich of incompatible elements i.e.: strontium, rubidium, barium, potassium, thorium, niobium and group of rare earth elements.
Keywords: geochemistry, magma, muria, mineralogy, petrography, tectonic
INTRODUCTION Background
Muria volcano has long been known as an anomaly of volcanoes in Java due to its different features. Indeed, this unusual magma emanation feature should have certain characteristics such as expressed in many igneous provinces with certain tectonic patterns. However, studying a lot of characteristic related to this issue is impossible at one time. Nevertheless, some attempts to provide information regarding to igneous petrogenesis in such from mineralogy and geochemical data are now considered to be more petrogenesis-oriented by many igneous petrologist.
the Muria petrogenesis
Research O The objectiv a. To ident
magma u analysis. b. To find o
character which is geochem c. Proposin volcano.
Location Muria v coast of C extending la is approxim longitude 1 different reg south, Pati west part o hours to reac cauldron fro about two h continuing Tempur cau
Fig. 1. Location
Scope of Re In attem discussion volcano, thi geological essential in igneous p geochemistr interrelated Muria petrog
Problems The problem this research a. What is
regardin geochem
a magma, s.
Objectives ves of the rese
ify characteris using petrogra .
out relation be ristic of Muria expressed in mical to its tect ng petrogenesi
volcano is lo Central Java, and known as mately at latitu 10o 53` east. gional sectors at east, and J of volcano. I ch the souther om Semarang hours more if to reach the uldron.
n map of Muria v
esearch mpt to avo
about petro is research is interests whi providing inf petrology: ry. Based
interests, ste genesis are tak
ms which need h are:
characteristic g to its minera mistry?
therefore to
earch are: stic of Muria aphy and chem
etween a erupted lava
mineralogy an tonic setting. is of Muria
cated in the , in a nort
Muria Penins ude 6o 37` sou
It belongs to including Ku Jepara at nort It takes abou rn flank or Ra g using vehicl f willing to t northern fla
volcano.
id broadenin genesis of s focused int ich believed formation rela mineralogy
on these eps to discus
ken carefully.
d to be reveale
of Muria mag alogy and thward sula. It ahtawu
le and
to relatio and tecto
Hypotheses Hypotheses a. Igneous of silica silica co b. Igneous probably some mi this valu c. Muria vo
evidence island ar (Sunda p
METHODO Research M
Methods divided int method, an main analys research a analysis. B study of ro analysis itse geochemica
Petrograph Study igneous ro preferred identificatio prepared in thickness, c for microsc instrument polarization exclusively of light and rock formin Interacti crystal will as optical pr mineral can according to
Igneous generally classificatio Petrology pr the mineral often the c
o those charac petrogenesis o onship betwee onic setting?
s
related to this rocks of Mur deficient rock omposition.
rocks of Mur y show high a inerals may pr ue.
olcano is susp e of transition rc (recent Java plate) volcanis
OLOGY Methods
s used during to survey m nd laboratory
sis techniques are petrograp
oth of them ocks mineral elf is further u al features.
hy Analysis of textural ocks beneath
instead on. Rock s n thin section
commonly use cope identific used in n microsco
designed for d matter or, in ng minerals res ion between
show a distin roperties. Fro n be determ o sequence in
rock cl refers to on by the IU
roposed by St mode cannot case for volc
teristics expre of Muria regar en those chara
s research are ria volcano con
ks regarding to
ria volcano wi alkalinity value
resent to expre
pected as an nal volcanism
a arc) to intra-sm.
this research method, desc method. Th s performed phy and ch are interrela logy, but ch useful in expr
characterist a microsco of mega ample shoul which has r ed in 0.03 mm cation. The pr petrograph ope, which studying inter this case, cry spectively.
light and c nct behavior k m this subjec mined one by
Fig. 2. lassification
standardized UGS Commit treckeisen (19 be determine canic rocks, t
2
ess to? rding acters
: criptive he two
in this emical ated in
emical ressing
tic of ope is ascopic
ld be eliable m thick rimary hy is
h is raction ystal of
chemical cla silica is use followed is s
Fig. 2. Systema its optical prop
Fig. 3. Flow igneous rocks u
Chemical A Determin major and tr analysis of method use and this is p and Devel Atomic Ene
assification of ed. The seque shown in Fig.
atic identification erties (Kerr, 1959
chart for the usage (Le Maitre
Analysis nation of an race elements f igneous r d in this rese provided by G opment Cen rgy Agency.
f total alkalis v ence that shou . 3.
n of mineral regar 9).
IUGS classifica
et al., 1989).
extensive ran s is desirable w
rock. Instrum earch is only Geological Re nter and Na
versus uld be
rding to
ation of
nge of within mental XRF, search ational
A variat K2O versus
useful wa composition rocks and th was propos Systematics (1986). Th QAPF cla proportions Streckeisen distinguishin rocks wi discriminati Rickwood distinguishin rocks will re rocks of the subdivided (K-series), series) in t Na2O; this
series refers During t spiderdiagra element of is adopted be compare calc-alkalin spiderdiagra
Flow Diagr Systema this researc below.
Fig. 4. Researc
tion diagram s wt. % SiO2
ay of disp nal range of
heir nomencl sed by Subc s of Igneous R his is also c
assification, of constitu
(1967). U ng the alkali ill refer ion diagram
(1989). An ng the alkali efer to Cox et
e alkaline ma into sodic (N
and highly terms of a p
subdivision s to Middlemo
this research, am for abu
igneous rock from Edward ed with typica e and am from Pearc
ram of Resear atically, steps
h might be s
ch’s flow diagram
of wt. % N or TAS pro playing the
terrestrial vo ature. This di commision o Rocks, Le Bas consistent wit based on uent minera Using this ine and subal
to alkali m compiled nother versio ine and subal
t al. (1979). F agma series m
Na-series), po potassic (h plot of K2O
of alkaline m ost (1975).
the data sou undance of ks of Muria v ds et al. (1991
al island arc h tholeiitic b ce (1983).
rch
s conducted seen in the di
m.
3
Na2O +
vide a wide olcanic iagram on the
s et al. th the
modal als by
TAS, lkaline i-silica d by
on in lkaline urther, may be otassic high-K versus magma
urce of trace olcano 1) will high-K basalts
RESULT A Petrologic F
For ease igneous ro mineral, ove of igneous r preferable a Note that, o volcano are to lower pa diagram. Fr separated in First is the s in feldspath near the bor dashed line silica un considerably ferromagnes near the line circle.
Fig. 6. (a) Clus rounded smalle trachyandesite and fine crystal
AND DISCUS Features
when giving ock origins erall mineral a rock samples i as seen in Ta overall igneou
more likely rt of double t rom this, it nto two distin
silica saturate hoid minerals rder of line A
circle. The ndersaturated
y richer in fel sian minerals e PF marked b
ster of olivine in er leucite crystals (40x, crossed pol l within lava in th
SSION
interpretation based on abundances an in QAPF diag able 1 and F s rocks from fall into the m triangle QAP
is can be f nct groups of ed rocks group
s, which plot AP marked by
other group
rocks g
ldspathoid an s, which plot by green dashe
(a)
(c)
olivine tephrite s scattered the en lar). (d) Borderin he right side (x40
n of all modal nd plot gram is Fig. 5. Muria middle F plot further rocks. p, lack t falls y blue
is the group, nd also t falls ed line
(40x, crossed pol ntire groundmass ng line in the cent 0, crossed polar).
Fig. 5. QAPF p
lar). (b) Phenocry (40x, crossed po ter of picture is di
plot of overall ign
(b)
(d)
yst of leucite in l olar). (c) Very lar ividing fossilifero
neous rock sampl
leucite tephrite, n rge crystal of san ous calcite in the
4
les.
It can b different mi have been magmatic a volcano. D explained u which is res composition erupted will in Fe, Mg, a expressed b may refer t olivine teph repeated fr erupted mag more silica-saturated c
Oxides
Major Elem In order characteristi plotted toget Fig. 7. Not the dividing marked by
Table 1: M
be summariz ineral-based r
produced i activity during Differentiation
using Bowen sponsible in c n. The first u l more likely and Ca conten by many of m
to undersatura hrite and leuc ractional crys gma will bec -rich; this is condition i.
s (%)
ment Charact to review the ics of rocks ther into TAS e that the en g line into the red dashed l
Mineral abundan
zed; there are rock groups in such a g genesis of like this c n’s reaction changing of m unmodified m to be basaltic nt, low silica c mafic mineral ated conditio cite tephrite. stallization o come progres referring to e.: andesite
Table 2: Major e
Sample 44.25
teristics overall alkali s, the result S diagram as s tire plot fall alkaline suite line circle. F
nces of all sample
e two which single Muria an be
series magma magma c, rich content s; this n i.e.: While occurs, ssively silica and
element analysis
C.1
i-silica ts are seen in
above e field Further
es for designation
trachyandes of magma will also m composition assimilation xenolith fo south flank proof that t Many calca been strong metamorphi which gone may still condition. T important p composition
data from Muria
Sample C 54.05
subdivision into the K-s Fig. 8. Sili intermediate correlated to petrography are similar
n of QAPF diagra
site, see Fig. assimilation akes further c n. The sign n with sedi und at the e of Muria vol this process areous parts fr gly recrystalli
ism during re e uncomplete showing fos This reaction i process which n.
Volcano.
C.2
of alkaline m series to high ica compositi e to basic-u o analysis of m y results, inter
to silica satu
am.
6. The involv with country changing of m nature of m imentary be eroded cauldr lcano gives a has been occ rom fossil for zed due to th emelting by m ed. The othe ssil form in
s occurred as h modifies m
Sample C. 55.42
magma series, -K series as s ion is ranged ultrabasic. If
modal mineral rmediate rock urated rocks
5
vement y rock magma magma ed by
and basic-u similar to si As susp identificatio express the minerals. Ig are surely Respect to minerals wh potassium orthoclase albite, neph an essentia associated minerals ar alkaline affi
Fig. 7. TAS plo
Fig. 8. Alkaline
As prev petrologic f has support also showin rock groups magmatic a volcano. F
magma a
ultrabasic roc ilica undersatu pected fro on, major elem
e existing o gneous rocks f
to be alkali o this alkal hich appear kn
elements or sanidine, eline, and leu al common with includ re present i nity of Muria
ot for overall sam
e magma subserie
viously writte features secti ting the petro ng two diffe s have been activity during Fractional c assimilation
ck group he urated rocks g om petrog
ments charact optically obs from Muria vo ine magma o line affinity, nown to be so bearing in Na-plagiocla ucite; and also accessory m des biotite. in expressing ’s magma.
mples.
es for overall sam
en in summa ion, chemical ological data erent
mineral-produced a g genesis of crystallization are respo
ere is group. graphic teristic served olcano origin. , key
odium-nclude ase or o such mineral These single Muria and onsible
processes chemical da about alkal The elemen are signatu evolution d and these e concentrated of magma b will also composition
Trace Elem Using in adopted fro spiderdiagra pattern of igneous ro spiderdiagra original ve comparing high-K calc from Pearce environmen Fig. 9.
Relative elements (H and Lu are n close to reflecting Group of th displaced up Ti. This el enrichment light REE pattern of ‘h This pattern island basa becomes incompatibl one kind o signature.
The sp trough at N anomaly, th petrogenesis subduction be paid wh means real concentratio MORB. Th far more e makes Nb a looked ca considerably
taking on ata are able fo
ine affinity o nt K and Na; a ure of furthe due to fractio elements are d in the crust. by assimilation
further mo n.
ment Charact ncompatible om Edwards am is created
trace elemen ock of Mur
am is already ersion in or patterns for c-alkaline an e (1983). Desi nt of Muria v
ely less mob HFSE) Th, Nb not much disp MORB co pre-subducti hese heavy el pward or enri lements enric pattern of som from La to humped’ or ra n is usually alt (OIB) c signature th le element ri of intra-plate
piderdiagram Nb which often
his is consider s of island occurs. It is n hereas trough l depletion in on is truly st he surrounding
enriched exc appears as tro arefully, Nb y enriched for
here. How or further expl
of Muria’s m and of course er step of m onal crystalliz tend to be . The contami n with crustal odify the m
eristics trace elemen
et al. (1991 d to understan nt abundances
ria volcano. rearranged fr rder to adap
typical islan nd tholeiitic b ignation for te volcano is sho
ile or heavy b, Zr, Ti, Dy, Y placed and rela
omposition ion characte lements are s iched at Nb, Z chment, along me LILE; esp
Eu, makes o ather convex appearing in composition
he existenc ich magma s volcanic imp
have disti n called as ni red to be rela
arc setting need an attent at Nb is not n Nb becaus till close to t g element plo
ept Nb itsel ough. But whe b itself is
r about two o
6
wever, laining magma. Si too, magma zation, highly ination l rocks
basalts ectonic own in
y trace Y, Yb, atively which eristic. slightly Zr, and g with
ecially overall shape. ocean which ce of
source, portant
7
times from MORB value although the surrounding trace element abundances are higher or have far more richer and still make a trough-look at Nb. But this trough is not as strong as that displayed by purely subduction-related magma.
Wilson (1989) on her book wrote distinguishing feature when reading spiderdiagram patterns of different magma sources:
“Compared to the relatively smooth shapes of the MORB and OIB spiderdiagrams, that of the subduction-related basalt is strongly spiked. …, the positive spikes are mostly a consequence of components added to the mantle source of basalts by subduction zone fluids [p. 21].”
Spiderdiagram pattern is not only rather spiked but also convex. The causes of spiked-convex feature are due to incompatible trace element addition which has been explained above. This transitional pattern indeed marks transitional tectonic environment of Muria volcano from island arc to intra-plate environment; or to OIB according to statement of Wilson (1989). Take a look on real geological setting of Muria volcano, the island arc respects to recent Java Arc, and then the intra-plate environment respects to Sunda plate or southeast part of the great Eurasian plate. The matching of spiderdiagram pattern for Muria volcano to standard pattern used by Pearce (1983) and its designation of tectonic environment might be seen in Figure 4.37 which is placed in the next page.
Petrogenetic Model of Muria Volcano Muria magma has already passed such a complex processes in its genesis involving subduction-modified magma sources at mantle depth and contamination of crustal rocks in the upper level. Explanation for overall petrogenetic of Muria volcano is written below, while the visualization model might be seen in Fig. 10. Assimilation due to contamination of magma by sedimentary rocks is strongly proven by the evidence of remained large xenoliths consist of sedimentary origin rock in Rahtawu cauldron. Igneous rocks from Muria volcano are product of the alkaline magmatism with emphasis on potassic character. The magma
generated a oceanic ridg plate motion continental concentrated can be mov mechanism margins. Th magma ge lithosphere
Fig. 9. Designa
at the spreadin ges, and then n in passed tim
margins. L d in the crus ved into mag along the he next is th eneration fro at intra-plate
ation of spiderdia
ng centers of n it was mov mes until arri LILE is str
stal rocks wh gma by subd
destructive he involveme om subconti
setting benea
agram pattern of M f mid-ved by
ved to rongly hereas duction plate ent of inental ath the
Muria volcano to
Sunda pla usually sh incompatibl HFSE. And been includ convection plate slab m different subduction-generate Mu
its tectonic envir
ate. An intr hows enric le elements, d these comp ded into the m above the must have bee magma gen -modified ma
uria magma.
ronment.
ra-plate volc chment of
both in LIL ponents must magma. The m
subducted o en mixed thes nerations in agma source
8
canism most E and t have mantle oceanic se two nto a
Fig. 10. Visual
CONCLUS Igneous intermediate regarding t molecule we to 55.42 in volcano fall due to its molecule we = 9.24 to 10 ranging from minerals wh alkalinity v leucite. Mu transitional and intra-c regarding to
ACKNOWL The au lecturers Mr Rachwibow critical revi research. Th and my s encouragem Permanadew elements. T analyses of Thanks to preparation. Aribowo, M Subandrio,
ization of summa
SION
rocks from M e to ultr to its silica eight percenta
wt.%. Magm l into the alka s high alka
eight percenta 0.1 in wt.%, t m K-series to hich present t value are al uria volcano
volcanism b continental p o its tectonic se
LEDGEMEN uthor wishes
r. Hadi Nugro o for his guid iews during hanks to my p sister for fu ments. Thank wi for XRF Thanks to Mr f trace and ra Mr. Sumaji Discussions Mr. Tri Wi
Bakhtiar
arized process inv
Muria volcano rabasic cha abundances age of SiO2 =
ma series of aline magma alinity value
age of Na2O +
then its subdi high-K series to express thi lkali feldspar
is a typic between islan plate enviro etting.
NT
to thank ho and Mr. Pr des, correction execution o parents, my b und supports ks to Mrs.
analyses of rs. Farida for are earth elem
for thin se s with Mr. inarno, Mr.
Safrihadi, V
volved during gen
o have aracter with 44.25 Muria series with + K2O
ivision s. Key rakosa ns, and of this brother
s and Sam major r XRF ments. ections Yoga Joko Vahyu
neration of Muria
Vanny H. Vanadia Ma developing volcano. Th wishes to s Geology of the author i have kindly succeeding
REFEREN
1991. Ev for the Zone an Genesis Petrolog Universi Kerr, P. F
Tokyo: K Le Bas, M.
A. & Z Classific on Tota of Petro Universi Le Maitre,
Keller, Sabine,
a magma.
., Dwandari artadiastuti ha ideas on pet hanks to Ikh share referenc f Indian Arch is grateful to y given suppo
the completio
NCES , Bell, J. D., The Interpre London: G
C., Menzies, M vidence from
Interplay of nd Intraplate of Alkaline gy. 555 – 59
ity Press. F. 1959. O Kogakusha.
J., Le Maitre, Zanettin, B. cation of Vol al Alkali-Silic logy. 745 – 7 ity Press.
R. W., Batem J., Lameyre, P. A., Schmid
Ralanarko, ave been valua trogenesis of hwannur Adha
ce books rela hipelagoes. F any individua orts at any k on of this writi
& Pankhurst etation of Ig George Allen
M., & Thrilwa Muriah, Indo f Supra-Subd e Processes i Magma. Jour 2. London: O
ptical Miner
R. W., Streck 1986. A Ch lcanic Rocks ca Diagram. J 50. London: O
man, P., Dude J., Le Bas, d, R., Sorense
9
Finally, al who kind inings.
t, R. J. gneous n and
all, M. onesia, duction in the rnal of Oxford
ralogy.
keisen, emical Based Journal Oxford
Streckeis Zanettin Igneous Recomm Union Subcomm Igneous from A W Classific http://ww Middlemost
Clan. 33 Pearce, J.
continen
APPENDIX
sen, A. L., W , B. 1989. A
Rocks and G mendations of
of Geol mission on t Rocks. Retrie Web Browser cation of ww.geolab.edu t, E. A. K. 7 – 364. Earth A. 1983. T ntal Lithosph
X
Wooley, A. A Classificati Glossary of f the Interna logical Sc the Systemati eved May 23, r Flow Chart f Igneous R u
1975. The h-Science Rev The Role of
here in M R., & ion of terms: ational iences ics of
2007, for the Rocks:
Basalt views. Sub-Magma
Genesis Natwich Rickwood,
Within Oxides 247 – 26 Streckeisen
Nomenc Retrieve Browser Classific http://ww Wilson, M
London:
at Destructi h: Shiva
P. C. 1989 Petrologic Di of Major an 63. Lithos.
, A. L. 1967 clature of ed May 21, 2
r Flow cation of ww.geolab.ed M. 1989. Ign : HarperCollin
ive Plate Ma
9. Boundary iagrams whic nd Minor Ele
. Classificatio Igneous R 2007, from A
Chart for Igneous R du
neous Petroge nsAcademic.
10
argins.
Lines ch Use ments.
on and Rocks. A Web
the Rocks:
