Mazzini EGU 2018: Volkanisme Lumpur di Kalang Anyar

EGU2018-10363 Mazzini

From 

https://meetingorganizer.copernicus.org/EGU2018/posters/27155

Geophysical Research Abstracts, Vol. 20, EGU2018-10363-2, 2018, EGU General Assembly 2018 © Author(s) 2018.

Vulkanisme lumpur subaqueous dan subareal di Kalang Anyar, Jawa, Indonesia

Subaqueous and and subareal mud volcanism at Kalang Anyar, Java, Indonesia

Adriano Mazzini (1), Alessandra Sciarra (2), Matteo Lupi (3), Alwi Husein (1,4,5)

(1) Centre for Earth Evolution and Dynamics, University of Oslo, Oslo, Norway (adriano.mazzini@geo.uio.no),

(2) Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy,

(3) Earth and Environmental Science, University of Geneva, Geneva, Switzerland,

(4) Institut Teknologi Sepuluh November, Surabaya, Indonesia,

(5) PPLS, Surabaya, Indonesia

Tinjauan EGU 2018

Ditinjau Oleh Dr. Hardi Prasetyo

"Sciences Manager" Misi Nasional Penanggulangan Bencana Lusi 2007-2017

Abstrak

Provinsi minyak di Jawa utara (The northern Java petroleum province) ditandai oleh penyebaran struktur pembubungan modern dan purba (by distributed modern and palaeo piercement structures).

Sebagai pengamatan adanya interaksi antara pengapungan serpihan gravitatif-tidak stabil (witnessing the diffused interaction between gravitatively-unstable buoyant shales), aktivitas patahan, hidrotermal, dan generasi hidrokarbon (faulting, hydrothermal activity, and hydrocarbons generation).

Sehingga bagian timur laut Jawa menampung setidaknya 6 gunung lumpur tidak aktif (hosts at least 6 dormant mud volcanoes), beberapa kawah purba yang terkubur (buried palaeo vents) diapir, dan situs semburan Lusi yang spektakuler (the spectacular Lusi eruption site).

Sistem Patahan Watukosek, yang berawal dari kompleks vulkanik Arjuno Welirang (The Watukosek fault system, originating from the Arjuno Welirang volcanic complex), mengarah ke Timurlaut pulau Jawa  sebagai induk  sistem geysering klastik Lusi (hosting the Lusi clastic-geysering system),  Kepundan palaeo Porong (the Porong palaeo vent), Gunung-gunung lumpur Kalang Anyar, Gunung Anyar, dan Pulungan.

Kalang Anyar mencakup area di  permukaan selus ~6 hektar yang menampilkan puluhan situs rembesan kecil yang tersebar yang sewaktu-waktu menyemburkan minyak, gas, lumpur dan air.

Geokimia mengungkapkan bahwa gas yang merembes didominasi metana dengan sebagian kecil hidrokarbon yang lebih berat (the seeping gas is methane-dominated with small portions of heavier hydrocarbons)

Asal usul metana campuran-termogenik (The mixed-thermogenic origin of the methane) digabungkan dengan potensi pertubasi geothermal (is coupled with potential geothermal perturbation) seperti yang ditunjukkan oleh nilai isotop CO2.

Isotop Helium juga mendukung beberapa masukan gas bersumber lebih dalam (Helium isotopes also support some input of deeper sourced gas) yang mungkin bermigrasi di sepanjang sistem patahan (migrating along the fault system).

Geokimia air menunjukkan bahwa air asin merupakan perpaduan antara air formasi laut dengan cairan illitisasi (that brines are a mix of marine formations waters with illitization fluids).

Hal ini mengindikasikan bahwa semburan lumpur yang kuat (This indicates that vigorous mud eruptions) mampu secara bertenaga mengangkat klastik (able to powerfully eject clasts) yang berasal dari beberapa formasi  yang terdapat masa lalu (from different formation occurred in the past).

Kerang yang diawetkan dengan baik (Well preserved shells) juga umum didapatkan, hal ini menunjukkan bahwa daerah tersebut pernah berada dalam kondisi bawah air (the area was once located in underwater conditions).

Blok berukuran meteran dan punggungan karbonat kecil (Meter sized blocks and small carbonate ridges) terdapat di berbagai daerah di tepi zona kawah.

Blok-blok karbonat tersemenkan ini mengandung sedimen silisiklastik yang relatif sedikit dan berlimpah cangkang chemosymbiotic.

Analisis isotop karbon dari semen karbonat tersebut, menunjukkan nilai negatif yang mengidentifikasi senyawa ini sebagai methanogenic chemoherms.

Sama halnya endapan-endapan karbonat yang serupa didokumentasikan secara luas dari situs rembesan pantai modern dan fosil (from modern and fossil offshore seepage sites).

Hasil menunjukkan bahwa gunung lumpur Kalang Anyar telah aktif sejak daerah tersebut terendam oleh lautan (that Kalang Anyar mud volcano has been active since the area was submerged by the ocean) dan bahwa presipitasi karbonat yang dimediasi mikrobiologi (microbially-mediated precipitation of carbonates) sedang berlangsung selama terjadi rembesan metana subaqueous di lokasi kawah (ongoing during the subaqueous methane seepage at the crater site).

Subaqueous and and subareal mud volcanism at Kalang Anyar, Java, Indonesia

Abstract

The northern Java petroleum province is characterized by distributed modern and palaeo piercement structures witnessing the diffused interaction between gravitatively-unstable buoyant shales, faulting, hydrothermal activity, and hydrocarbons generation.

The northeast of Java hosts at least 6 dormant mud volcanoes, several buried palaeo vents and diapirs, and the spectacular Lusi eruption site.

The Watukosek fault system, originating from the Arjuno Welirang volcanic complex, extends towards the NE of the island hosting the Lusi clastic-geysering system, the Porong palaeo vent, and the Kalang Anyar, Gunung Anyar, and Pulungan mud volcanoes.

Kalang Anyar extends over a surface of ∼6 hectares displaying dozens of scattered small seepage sites that intermittently burst oil, gas, mud and water.

Geochemistry reveals that the seeping gas is methane-dominated with small portions of heavier hydrocarbons.

The mixed-thermogenic origin of the methane is coupled with potential geothermal perturbation as indicated by CO2 isotopic values.

 Helium isotopes also support some input of deeper sourced gas possibly migrating along the fault system.

Water geochemistry indicates that brines are a mix of marine formations waters with illitization fluids.

Clasts with different lithologies are scattered throughout the area.

This indicates that vigorous mud eruptions able to powerfully eject clasts from different formation occurred in the past.

Well preserved shells are also common indicating that the area was once located in underwater conditions.

Meter sized blocks and small carbonate ridges are present at various localities on the edges of the crater zone.

These carbonate-cemented blocks contain a relatively small amount of siliciclastic sediments and abundant chemosymbiotic shells.

Carbon isotope analyses of the carbonate cement reveals negative values identifying these as methanogenic chemoherms.

Similar carbonate deposits are broadly documented from modern and fossil offshore seepage sites.

Results indicate that Kalang Anyar mud volcano has been active since the area was submerged by the ocean and that here microbially-mediated precipitation of carbonates was ongoing during the subaqueous methane seepage at the crater site.