Chemical and Petrography Analysis in Petrogenesis Study of Muria Volcano, Central Java - Diponegoro University | Institutional Repository (UNDIP-IR)

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

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2010

SITY

ANALYSI

ANO, CEN

FT

SETYA

RING

UDY PRO

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NTRAL JA

OGRAM

AVA

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.

In order to make a more petrogenesis-oriented approach, this research is performed by two way identification which each other are closely related, petrography and chemical analysis. Petrography is preferable in identifying optical features from rock forming minerals and texture which strongly indicate crystallization processes within igneous rocks. Chemical analysis is also desirable as hint at mineral content even though it tells nothing about rock textures. These two way identification are intended to be combined in order to make a comprehensive igneous rock data within the Muria. This combination would really be a help to get the brighter answers in discussing

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 o its mical as nd north thward sula. It th and o three udus at th and ut two ahtawu le and try for ank or ng of Muria to two to be ated to and two ss the . ed in gma

b. What do c. How is p

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 : nsist o its ll e, ess from -plate can be 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 certain known t, each y one used rock ttee in 967). If ed as is then a

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

during iagram

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.

note that nidine in left side

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 SiO2

TiO2

Al2O3

Fe2O3

MnO MgO CaO Na2O

K2O

P2O5

NiO ZrO2

CuO SrO V2O5

Cr2O3

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 0.927 18.28 8.3 0.161 6.02 11.23 3.96 5.28 1.13 0.011 0.033 0.009 0.118 0.043 0.051 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 5 7 8 1 2 3 6 8 2 3 94 8 6 9 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 0.439 19.07 4.71 0.149 0.892 4.56 4.49 5.61 0.311 0.0072 0.0467 0.0022 0.154 0.0184 0.0021 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 0.487 19.85 5.57 0.154 1.2 3.98 3.5 5.98 0.403 0.0112 0.0021 0.0014 0.0499 0.0031 0.189 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 ron in strong curred. rm has hermal magma er part good one of magma 3 it falls seen in d from it is l using ks here group,

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 g the mples. ary of l data which -based 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 magma nt data 1), the nd the s from This rom its pt the nd arc 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 inctive iobium ated to where tion to really se Nb that of ots are lf that en it is s has

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

series ranged from K-series to high-K series. Mineralogy data has proven alkaline related minerals association within igneous rocks such as leucite, alkali feldspar, plagioclase, olivine, clinopyroxene, hornblende, and biotite. These minerals association express the alkaline magma affinity with some of them are potash-bearing minerals e.g.: feldspathoids, alkali feldspars, and biotite. As the element of K, Na, and Si which is relatively concentrated in the more evolved magma, it also can be related to their behavior of tendency being concentrated in the crustal rocks. These elements are termed lithophile in geochemistry because of their tendency for being concentrated in silicate phase. Crustal rocks which in case of petrogenesis of Muria volcano are the sedimentary rocks which induced assimilation of Muria magma, and now remained as xenoliths. Looking at the position from the main island arc of Java, Muria volcano occurred in the back arc setting where sediments tend to be deposited in large amount. This position of occurrence may explain why Muria magma suffered high contamination and resulting in the alkaline affinity magma. Igneous rocks from Muria volcano also having a set of silica spectrum ranging from ultrabasic to intermediate, which also to be a proof of differentiated magma product. Modification of magma composition results might be explained using Bowen’s reaction series where the last minerals formed in the series proving the more differentiated or evolved magma product. The more differentiated magma is relatively younger than undifferentiated one within period of volcanic activity of Muria volcano. However, to ensure the source of Muria magma origin, this research also focused its concern on trace element. The trace element analysis has resulting in a transitional pattern of magma sources between two different tectonic settings. First is the involvement a subduction-zone in the south of Java which responsible in producing LILE concentrated fluid from remelting of oceanic crust of oceanic plate of Indian plate and subducted sediments from both reworked continental rocks of Sunda plate and oceanic sediments. In reality, oceanic crust in general has trace element composition similar to MORB because it is actually rocks which were

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 s high r and cal of nd arc

nment

guide 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 Cox, K. G. 1979. T Rocks. Unwin. Edwards, C

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

, and able in

Muria a who ated to Finally, al who kind in

ings.

t, R. J. gneous n and

all, M. onesia, duction in the rnal of Oxford

ralogy. keisen, emical Based Journal Oxford ek, A.,

M. J., en, H.,

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: enesis.

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 SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 NiO ZrO2 CuO SrO V2O5 Cr2O3 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 0.927 18.28 8.3 0.161

6.02 11.23

3.96 5.28 1.13 0.011 0.033 0.009

0.118 0.043 0.051

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

5 7 8 1 2

3 6 8 2 3 94

8 6 9

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 0.439 19.07 4.71 0.149 0.892 4.56 4.49 5.61 0.311 0.0072 0.0467 0.0022 0.154 0.0184 0.0021 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 0.487 19.85 5.57 0.154

1.2 3.98

3.5 5.98 0.403 0.0112 0.0021 0.0014 0.0499 0.0031 0.189 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

ron in strong curred. rm has hermal magma er part

good one of magma

3

it falls seen in d from it is l using ks here group,

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 g the mples. ary of l data which -based 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 magma nt data 1), the nd the s from This rom its pt the nd arc 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 inctive iobium ated to where tion to really se Nb that of ots are lf that en it is s has

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

series ranged from K-series to high-K series. Mineralogy data has proven alkaline related minerals association within igneous rocks such as leucite, alkali feldspar, plagioclase, olivine, clinopyroxene, hornblende, and biotite. These minerals association express the alkaline magma affinity with some of them are potash-bearing minerals e.g.: feldspathoids, alkali feldspars, and biotite. As the element of K, Na, and Si which is relatively concentrated in the more evolved magma, it also can be related to their behavior of tendency being concentrated in the crustal rocks. These elements are termed lithophile in geochemistry because of their tendency for being concentrated in silicate phase. Crustal rocks which in case of petrogenesis of Muria volcano are the sedimentary rocks which induced assimilation of Muria magma, and now remained as xenoliths. Looking at the position from the main island arc of Java, Muria volcano occurred in the back arc setting where sediments tend to be deposited in large amount. This position of occurrence may explain why Muria magma suffered high contamination and resulting in the alkaline affinity magma. Igneous rocks from Muria volcano also having a set of silica spectrum ranging from ultrabasic to intermediate, which also to be a proof of differentiated magma product. Modification of magma composition results might be explained using Bowen’s reaction series where the last minerals formed in the series proving the more differentiated or evolved magma product. The more differentiated magma is relatively younger than undifferentiated one within period of volcanic activity of Muria volcano. However, to ensure the source of Muria magma origin, this research also focused its concern on trace element. The trace element analysis has resulting in a transitional pattern of magma sources between two different tectonic settings. First is the involvement a subduction-zone in the south of Java which responsible in producing LILE concentrated fluid from remelting of oceanic crust of oceanic plate of Indian plate and subducted sediments from both reworked continental rocks of Sunda plate and oceanic sediments. In reality, oceanic crust in general has trace element composition similar to MORB because it is actually rocks which were

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 s high r and cal of nd arc

nment

guide 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

Cox, K. G. 1979. T Rocks. Unwin. Edwards, C

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

, and able in

Muria a who ated to Finally, al who kind in

ings.

t, R. J. gneous n and

all, M. onesia, duction in the rnal of Oxford

ralogy. keisen, emical Based Journal Oxford ek, A.,

M. J., en, H.,

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: enesis.