23Occurrence of Phillipsite Mineral in Sub-seafloor of Roo Rise ... Dida Kusnida

OCCURRENCE OF PHILLIPSITE MINERAL IN SUB-SEAFLOOR OF ROO RISE-INDIAN OCEAN :

A TECTONIC EROSION SYNTHESIS

Dida KusnidaMarine Geological Institute of Indonesia

Jalan DR. Djundjunan 236, Bandung-40174e-mail: didakusnida@mgi.esdm.go.id

Received : 10 October 2008, first revision : 29 December 08, second revision : 01 February 2009,accepted : February 09

ABSTRACT

A single deep-sea core (MD982156) of 30.30 meters long which is obtained during the MD III-IMAGESIV Expedition from Roo Rise - Indian Ocean in 1998 was studied. Down to 30 meters of the corelength, the sediment consists of abundance planktonic foraminiferas. Below 30 meters, it is mostlycomposed of phillipsite mineral-rich sediment that is associated with nannoplanktons.The Paleocene authigenic phillipsite minerals associated with nannoplanktons is separated from LateMiocene to Holocene planktonic foraminiferas rich-sediments by hiatus. This hiatus or non deposi-tional in Roo Rise suggest be triggered by long Cenozoic tectonic erosion.

Keywords: phillipsite, Roo-Rise, Indian Ocean, authigenic, hiatus, tectonic erosion

1. INTRODUCTION

In 1998, the MD III-IMAGES IV Expedition in theIndonesian waters and the Indian Ocean has beenconducted in the framework of IMAGES Program(International Marine Global Changes Study), inwhich, deep sea floor sediment coring programfrom IGBP-PAGES (International Geosphere–Bio-sphere Program Past Global Changes) affiliatedwith SCOR (Scientific Committee on OceanicResearch) has also been taken. The aim of theexpedition was to take inventory the sea floor sedi-ment samples from the Indonesian waters with agiant piston core. This expedition was executedusing the France RV Marion Dufresne. Two scien-tists from the Marine Geological Institute of Indo-nesia were involved and worked on biostratigra-phy aspect of core MD982156 taken from 11Ú33.31’S and 112Ú 19.72’ E (Figure 1), preciselyat the northern slope of Roo Rise toward the JavaTrench - Indian Ocean at water depth 3884 meters(Figure 2).

Adisaputra and Hartono (2004) stated that thelower part of the MD982156 core (30 - 30.30 mbsf) consisted of nannoplanktons rich-sedimentswithout foraminiferas content. In contrast; from 30m bsf to the sea floor, it consisted of planktonicforaminiferas rich-sediments. On the basis ofScanning Electron Microscope (SEM), Adisaputradan Hartono (2007) indicated the occurrence ofphillipsite mineral at 30 m to 30.30 m bsf.

The origin of phillipsite mineral in deep marineenvironment has been the topic of considerablediscussion among mineralogists (Knox et al, 2003and Diekmann et al, 2004). However, this articletries to describe the occurrence of Paleocenephillipsite-rich sediments observed in sub-seafloorsamples MD982156 drilled and collected duringthe MD III-IMAGES IV Expedition at the Roo Rise-Indian Ocean in 1998. The aim of the study is tosynthesize the absence of post Paleocenephillipsite mineral within the core since it was ob-tained from the pelagic sediments. The mineral is

24 INDONESIAN MINING JOURNAL Vol. 12, No. 13, February 2009 : 23 - 27

presumed to be preserved within the long succes-sion of the sediments and free from erosion aswell.

Figure 1. Map showing the location of core MD982156 in the Roo Rise producein Figure 2

Figure 2. N-S profile across Roo Rise - Java Forearc Ridge where CoreMD982156 is location

2. STUDY METHOD

Sediment samples were taken from every 1.50meters interval of 30.30 meters length of coreMD982156. Therefore, 21 samples were obtained.

Fifty mg from the top part of each sample wasthen sorted using 150 mµ shaver and dried at 50ºC. A small part of each samples were then used

for Scanning Electron Microscope (SEM) purposeswith magnification of 20,000x for individual photo-graphs. Time boundaries within core MD982156were adopted from the time zone interval made byAdisaputera and Hendrizan (2008).

25Occurrence of Phillipsite Mineral in Sub-seafloor of Roo Rise ... Dida Kusnida

3. RESULTS

In general, sediments within core MD982156 (Fig-ure 3) consist of calcareous clays and marls,brownish-white to grayish-white tuffaceous clay.It contains abundance of foraminiferas and nanno-planktons until 30 meters depth of the core. Downfrom 30 to 30.30 meters (bsf) of the core, the sedi-ments consist of phillipsites minerals with variousforms. The Scanning Electron Microscope (SEM)

photograph indicates that the basic forms ofphillipsite minerals is bounded by cement/matrixdominated by nannoplanktons. The planktons formvarious binding such as straight, T-form, diagonaletc (Figure 4). These phillipsites contains openchannels (Figure 5). Other cryptocrystalline masswithin core are gibbsite or hydragilites associatedwith nannoplanktons. The thickness and exten-sion of this layer are still unknown.

Figure 4. Various binding of phillipsitemineral in the study are Photo-graph coutesy of Adisaputra 2008

Figure 3. Stratigraphic column of core MD982156

Figure 5. Phillipsite minerals bounded bymatrix nannoplanktons. Photo-graph coutesy of Adisaputra 2008

26 INDONESIAN MINING JOURNAL Vol. 12, No. 13, February 2009 : 23 - 27

According to Husaini (2006), phillipsite mineral wasnever found in Indonesia as its studies so far weremainly conducted on land. Adisaputra and Hartono(2007) stated that the mineral was only found asauthigenic origin within the deep sea. It possiblyderived from tephra as the volcanic product. Ac-cording to Amethyst Galleries Inc. (2008), phillipsiteis one of the rarest zeolites and forms interestingaggregates that are commonly clustered into brightwhite sphericules or balls with a rough crystallineor silky surface. Empirical formula of phillipsite isKCaAl3Si5O16-6H2O, while environmentally it isfound as common zeolite in volcanic rocks, oreveins, diagenetically altered rhyolitic vitric tuffs,saline lake deposits, and ocean floor sediments.

Gibbsite or hydragilite in the study area (Figure 6)forms cryptocrystalline masses, goldish-whitecolour and pearly lustre. According to Betekhtinin Adisaputra and Hartono (2007), it was possiblyderived from the decomposition and hydrolysis ofaluminium-bearing silicates, partly in the courseof hydrothermal process at a comparatively lowtemperature, but chiefly from surface weathering,mainly under tropical and subtropical climate con-ditions.

as are most other zeolites. The well-preserved LateMiocene to Holocene sediment record within coreMD982156 possibly shows evidence of a hithertounknown Eocene to Middle Miocene tectonic cir-cumstances. Lithological and biogenic variationspresent within core give insights into possibly mid-Cenozoic environmental changes in terms of tec-tonic activities.

Diekmann et al (2004) stated that the original deepsea phillipsite minerals, formed from surfaced rockfragment, derived from volcanic products. Thisnucleus was later altered to phillipsite under alka-line, silica-undersaturated, low-temperature con-ditions through the length of sedimentary rock.Paleo-location of Paleocene phillipsite formationof this study can be presumed at least at the flank ofmid-oceanic ridge and far from the present location.

Present tectonic framework off Java is character-ized by convergence between Indian Oceanic –Australian Continental Plates with Eurasian Platethat established since Late Neogene. Recently,Kopp et al (2006) gave the evidence for oceanicRoo Rise erosion on the basis of a newly acquiredgeophysical data off central Java. They indicatethe local erosive processes in the wake of sea-mount subduction and documented by high-reso-lution bathymetric survey and show irregular trendof the deformation front sculpted by seamountcollision scars. Further, the authors indicate asubduction of oceanic basement relief which leadsto large-scale uplift of the forearc and outer arcridges (seamount?) giving way to isolate topo-graphic elevations such as Roo Rise. These tec-tonic evidences, presumes that the hiatus recordedwithin core MD982156 is possibly caused by tec-tonic erosion of Roo Rise. A well preserved LateMiocene to Holocene sedimentary in study areaindicates the relatively stable tectonic conditionssince Late Miocene. Therefore, why it is only thePaleocene phillipsite rich-sediments are left in thestudy area.

5. CONCLUSION

The occurrence of phillipsite at the lowest part ofcore MD982156 obtained from Roo Rise suggesteda volcanic activity during Paleocene. These min-erals were formed authigenically in deep sea. ThePaleocene phillipsite rich-sediments, overlain byLate Miocene to Holocene foraminiferas rich-sedi-ments indicates the occurrence of hiatus or nondepositional since Eocene to Middle Miocene. The

Figure 6. Gibbsite from the study area fromcryptocrystaline masses

4. DISCUSSION

Phillipsite is now known to be an abundant con-stituent of surface sediment covering vast areasof the Pacific seafloor where sedimentation rateare low and occur as an encrusting precipitatearound hot springs (Ghosh and Mukhopadhyay,1995). However, phillipsite is more commonlyfound in the vesicles or bubbles of volcanic rock

27Occurrence of Phillipsite Mineral in Sub-seafloor of Roo Rise ... Dida Kusnida

hiatus or non depositional recorded within corepresumed was caused by tectonic erosion orslumping of Eocene to Middle Miocene sedimen-tary covers of Roo Rise off Java at least since lateNeogene tectonic activities.

ACKNOWLEDGEMENTS

The author wishes to thank and high appreciationsProfessor Ris. Mimin K. Adisaputra for her permis-sion to work on core and use the material for thisarticle. The author also wishes to thank Mr. Hartonoand Mrs. K.T. Dewi from the Marine GeologicalInstitute for valuable discussion. I thank Mr. Wikandafrom Center for Geological Survey who helped inminerals preparation and photography using SEM(Scanning Electron Microscope) analyses.

REFERENCES

Adisaputra, M.K. and Hartono, 2004. Late Miocene– Holocene Biostratigraphy of Single Core inRoo Rise, Indian Ocean, South of East Java.Bull. Marine Geological Institute, Vol 19, No.1,p. 27-48.

Adisaputra, M.K. and Hartono, 2007. The PhillipsiteMineral in Deep Sea Sediment from SingleCore in Roo Rise-Indian Ocean, South of EastJava, Indonesian Mining Journal, Vol. 10, No.9, p.39-43.

Adisaputra M.K. dan M. Hendrizan, 2008. “Hiatuspada Kala Eosen-Miosen Tengah di TinggianRoo, Samudera Hindia, Selatan Jawa Timur,

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