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Petrological Study of 1883 Krakatau Pumica

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Krakatau catastrophic eruption in 1883 produced a large amount of pumice in the form of pyroclastic flow or fall. At present, they are on Rakata, Sertung, Panjang, and Sebesi islands. The pumice as the major constituent, often accompanied by obsidian is petrographically and chemically analysed. Most pumice was white with some pink and blackish grey; in various from ash, sand lapilli to block. Mineralogically pumice and obsidian have the same composition. Volcanic glass groundmass about 90% volume and phenocrist about 10% volume. The phenocrysts are andesine and oligoclase (A*n_{25}*tos*n_{40}) , K-feldspar hypersten, augite and pigeonite, iron oxide and apatite. In the groundmass they are not uniformly scattered, but grouped

The texture of the pumice is hypocrystalline and vesiculated. Fibrous glasses often show sub parallel arrangement, swirl and pilotax- citic. Microlite feldspar also give, sub parallel arrangement texture. On some spicemens the crust part of the obsidian is gradually changed into pumice. These characteristics also are seen under the microscope, and the vesicles in this transitional zone are grouped; the cracks the obsidian are dominant. on

Chemically if S 10 2 is plotted versus K_{2}*O on Whitford (1975) variation diagram's and Middlemost (1980) S 10 2 vs K_{2}*O + N*e_{2}*O variation diagram's, the pumice is fallen into calc alkaline and dacitic in composition. Mineralogically they are an desitic. Fractination trend is dacitic- andesite to rhyolite.

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Ketersediaan

Informasi Detail

Judul Seri

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No. Panggil

PVG A.83-81

Penerbit

Bandung, Jawa Barat, Indonesia : Pusat Vulkanologi dan Mitigasi Bencana Geologi., 1983

Deskripsi Fisik

11 hlm

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

Petrological
Gunung Krakatau
1883

Info Detail Spesifik

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Pernyataan Tanggungjawab

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Informasi Lainnya

Kode Wilayah

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Pulau Dan Lembar Peta

Sumatera

Provinsi

Kepulauan Riau

Koordinat - Latitude

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Koordinat - Longitude

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Versi lain/terkait

Lampiran Berkas