Dody,
Tidak ada pertanyaan yang salah, yang ada adalah jawaban yang salah.
Yang saya maksud dengan subduction dan collision di utara Australia itu
adalah sektor benua Australia di selatan Timor-Tanimbar. Papua tak terkait ke
collision Timor-Tanimbar, tetapi betul ia sangat terkait dengan collision
island arc di selatan Pacific.
Berikut kutipan yang berhubungan dengan hal itu yang saya ambil dari makalah
saya dkk. terbaru (Collisional Orogens in Indonesia : Origin, Anatomy,and
Nature of Deformation -
Satyana et al., 2007) untuk pertemuan gabungan IAGI-HAGI-IATMI di Bali minggu
depan.
salam,
awang
CENTRAL RANGE OF PAPUA COLLISIONAL OROGEN
New Guinea is a type locality of island arc-continent collision during the
Cenozoic (Dewey and Bird, 1970). The northern half of the island is underlain
by a crystalline basement of oceanic crust with arc affinities derived from the
floor of the Pacific basin . The southern half of the island is composed of
passive margin strata overlying the Australian continental basement. Debate
exists, however, regarding the mechanism and timing of the events that created
the Central Range, mountainous backbone of the island.
The central portion of New Guinea, the Birds Body, can be divided into four
lithotectonic provinces from south to north (van Ufford and Cloos, 2005) : the
foreland basin, the Central Range fold and thrust belt, a metamorphic belt with
an overlying ophiolite complex, and an accreted oceanic arc complex. The name
Central Range of Papua collisional orogen is proposed for about 1300-km
(including the central range in PNG) long mountainous spine of New Guinea that
stretches from the Birds Neck up to the Papuan Peninsula.
Several tectonic episodes have been responsible forming the New Guinea (Hall,
2002; van Ufford and Cloos, 2005). Generally, most workers agree that Central
Range of Papua was formed by collision between oceanic or island arc complex
and Australian
continent. Dow and Sukamto (1984) interpreted that Irian Jaya section
(Indonesian Papua) of New Guinea is the result of interaction between Pacific
and the Australian Plates. Pigram et al. (1989) believed that collisional
complex consist of several arc complexes, oceanic plateaus, and microcontinent
amalgamation. Daly et al. (1991) involved the presence of probable oceanic
microplates in collisional processes.
Many theories exist for the Cenozoic tectonic evolution of New Guinea.
Hamilton (1979) proposed that the island is the result of the collision of the
Australian continent with a southfacing arc in the early Miocene, followed by
subduction reversal in the middle Miocene. In a regional tectonic synthesis,
Kroenke (1984) proposed that there were two major arc-continent collisions, and
that the New Guinea trench is a recently reactivated relict of an older oceanic
subduction zone. Milsom (1985) proposed that an Eocene collision was followed
by subduction reversal in the early Miocene to form the New Guinea trench,
which changed into left-lateral transform faulting in the late Miocene. Cooper
and Taylor (1987) proposed a doubly dipping oceanic plate, separating two
active volcanic arcs on the Australian and Pacific plates, zippered shut from
west to east since the Oligocene. In this model, the New Britain trench is a
part of the north-dipping subduction zone, and the Trobriand
trough is a relict of the south-dipping zone. Dow and Sukamto (1984) and Dow
et al. (1988) proposed that New Guinea is the product of two distinct
island-wide arc continent collisions : one is in the Oligocene (Oligocene
orogeny), and the other is in the latest Miocene (Melanesian orogeny).
Irian Jaya, as part of the island of New Guinea, has been the NE active
margin of the
Australian continent and Indo-Australian plate since at least the Eocene. As
the Australian continent moved rapidly to the north, the New Guinea margin was
involved in an oblique convergence with the Philippine, Caroline and Pacific
plates, causing subduction, terrane accretion and strike-slip faulting which
continue today. Late Miocene arc-continent collision has resulted in the
mountains forming the backbone of New Guinea, including the thrusted and folded
Miocene-Mesozoic sediments of the fold belt with significant hydrocarbon
accumulations in Papua New Guinea (PNG). Previous Oligo-Miocene collision has
been inferred from metamorphic cooling ages in northern New Guinea (van Ufford
and Cloos, 2005).
In the late Paleogene (25 Ma Hall, 1995, 1996) or very early Neogene
(Simandjuntak and Barber, 1996), the northern promontory of the Australian
Continent collided with an oceanic island arcs constructed on the southern
margin of the Philippine Sea Plate (Hall, 1996). This collision trapped Indian
oceanic crust between the northern margin of the Australian Continent and the
island arcs. The oceanic crust which underlay the oceanic island arc
subsequently uplifted as the result of the collision with the Australia
(presently southern Papua) forming the Central Ranges of Papua.
Hall (2002) and van Ufford and Cloos (2005) concluded that tectonic models of
New Guinea range from one discrete collisional event to prolonged accretion.
Many models show a single arc-continent collision. The likely complexity of
this region is conveyed on many published cross-sectional sketches of plate
interactions, which include postulated collisions, subduction polarity
reversal, and quite varied subduction polarities. Almost all advocate northward
subduction of oceanic crust north of Australia before collision of the
Australia margin with a south-facing arc. Few authors have proposed that the
northern Australian margin was an active margin and there was
southward-subduction beneath this margin before the active margin of north
Australian continent collided with an arc (e.g. Hill and Hegarty, 1987; Hill et
al., 1993; Monnier et al., 1999).
dody darmawan <[EMAIL PROTECTED]> wrote:
Pak Awang,
Kalau boleh saya sedikit komentar dan bertanya
mengenai statement Pak Awang bahwa "Papua tak terkait
dengan subduction dan collision di utara Australia".
Kalau saya lihat di peta tektonik, kalau tidak salah
kontinen Australia ini berbenturan (collision) dengan
Pasific Plate. Benturan ini menyebabkan terangkatnya
sebagian sediment Mesozoikum menjadi rangkaian
pegunungan tinggi diantaranya puncak Jaya Wijaya yang
merupakan pegunungan tertinggi di Indonesia. Benturan
itu pula menjadikan world class porphyry intrusion
berumur muda (Miocene) bisa terekspose ke permukaan.
Puncak dari intrusi porphyry biasanya terbentuk 2 -
5km below the surface. Berarti proses pengangkatan
akibat collision ini menyebabkan setidaknya 2000 -
5000m terangkatnya kerak ke permukaan. Mungkin kalau
boleh saya bilang "kita" tidak mungkin punya tambang
tembaga-emas Freeport kalau bagian utara Austrlia
tidak berbenturan dengan Pasific Plate ini. Kira-kira
apakah pertanyaan saya ini benar?
salam,
Dody Darmawan
Angkatan '88
Awang Satyana <[EMAIL PROTECTED]> wrote:
..................................................
Collision Australia-Timor Tanimbar terjadi di Early
Pliocene, saat itu PNG dan Papua sudah jauh maju ke
utara di kontinen Australia, dan PNG serta Papua bukan
di sektor yang berbenturan dengan Timor-Tanimbar; jadi
saya pikir keberadaan PNG/Papua tak terkait dengan
subduction dan collision di utara Australia.
salam,
awang
Vicky Amir <[EMAIL PROTECTED]> wrote:
.......................................
maaf pak awang ada pertanyaan lagi nih..
mengenai north subduction di utara India maupun
Australia, apakah benar
exist?dari paper storey tdk menyebutkan secara
signifikan mengenai
indikasi keberadaan north subduction selain sbduction
di proto-Pacific
margin..saya sampaikan saja di presentasi klo subduksi
utara ini
benar2ada maka indonesia tdk akan mempunyai papua
nugini seperti
sekarang ini...(all laugh) he2..mohon koreksinya pak
awang jika saya
salah dalam menginterpretasi hal tersebut...
Regards
Vicki R. Amir
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