HYDROTHERMAL MINERALIZATION IN JAILOLO WATERS, WEST HALMAHERA, NORTH MALUKU PROVINCE

Halmahera Island tectonically is divided into two main regimes, those are East Arm Regime (EAR) and West Arm Regime (WAR). Both regimes have very different characteristics where the EAR consists of Cretaceous ultramafic rocks and old red shale, while the WAR composed of Neogene sediment. The study area is an area with active tectonism shown by recent seismic activities and volcanic eruptions. Hydrothermal activity is indicated by rocks alteration of andesite, dacite, and diorite such as kaolinite, argilic and montmorilonite. Primary metal type mineralization occured in a strong altered volcanic rocks, while the secondary mineralization occured in the sedimentary placer. AAS, petrographic analysis, and mineralografi obtained mineral pyrite, manganese, chalcopyrite in rocks from coastal and marine offshore up to depth of 100 meters. Analysis of the 36 examples of seabed sediments, showed the presence of anomalous metal minerals of Au, Cu, Mn, and Fe those are content of Au 0.01 - 0.03 ppm; Cu 14-150 ppm; Mn 23-1050 ppm; and Fe 2-10%.Keywords: Jailolo waters, western arm regime (WAR), andesite, dacite and diorite intrusion rocks, mineralization of Au, Cu, Mn, and Fe. Pulau Halmahera tektonik dibagi menjadi dua rezim utama, yaitu East Arm Rezim (EAR) dan Westt Arm Rezim (WAR). Kedua rezim memiliki karakteristik yang sangat berbeda yang EAR terdiri dari batuan ultrabasa Kapur dan shale merah tua, sedangkan WAR Terdiri dari batuan sedimen berumur Neogen. Daerah penelitian sebagai daerah dengan tektonik dan vulkanik aktif yang ditunjukan dengan aktifitas gempa dan letusan gunungapi hingga sekarang. Aktifitas hidrothermal ditunjukkan oleh alterasi pada batuan andesit, dasit, dan diorite. Mineral ubahan yang terbentuk kaolinit, argilik dan montmorilonit. Tipe mineralisasi logam primer terdapat dalam batuan vulkanik terubah kuat, sedangkan mineralisasi sekunder terdapat dalam sedimen plaser. Hasil analisis AAS, petrografi, dan mineralografi didapatkan mineral pirit, mangan, kalkopirit pada batuan di pesisir dan laut lepas hingga kedalaman 100 meter. Hasil analisis terhadap 36 sedimen dasar laut, menunjukan adanya kandungan mineral logam Au,Cu, Mn, dan Fe dengan kadar Au=0.01 - 0,03 ppm; Cu 14-150 ppm; Mn 23-1050 ppm; dan Fe 2-10% . Kata kunci: Mandala lengan barat (MLB), batuan intrusi andesit, dasit, dan diorit, mineralisasi Au, Cu, Mn, dan Fe, Perairan Jailolo, Halmahera Barat.

Newfoundland Neogene sediment drifts: transition from the Paleogene greenhouse to the modern icehouse

This workshop brought together specialists from various fields to develop a drilling proposal to fill the "Oligo-Miocene Gap" that exists in our understanding of the functions of Earth's systems. We propose to establish the first continuous high-deposition record of the Oligo-Miocene through new International Ocean Discovery Program (IODP) drilling in the North Atlantic to allow the development of a continuous Neogene cyclostratigraphy and to enhance our knowledge of Oligo-Miocene ocean–ice–climate dynamics. The workshop was held in Heidelberg from 15 to 17 September 2014 funded by ESF (EARTHTIME EU), NSF, and the ECORD MagellanPlus Workshop Series Program. A total of 24 participants from six different countries (Australia, France, Germany, the Netherlands, United Kingdom, and United States) attended the workshop, including several early career stage researchers. We discussed certain aspects of Cenozoic paleoceanography and paleoclimate and how the gaps in the Oligo-Miocene could be filled using scientific drilling. The ultimate goal of the workshop (to submit a pre-proposal to IODP) was achieved (IODP Proposal 874-pre was submitted 1 October 2014). Our workshop consisted of overview presentations followed by self-selected breakout groups that discussed different topics and produced text and figures for the proposal. Here, we give a short overview of the major topics discussed during the workshop and the scientific goals presented in the resulting IODP pre-proposal.

Pressure and fluid dynamic characterisation of the Dutch subsurface

This paper presents and discusses the distribution of fluid and leak-off pressure data from the subsurface of onshore and offshore Netherlands in relation to causes of formation fluid overpressure and the permeability framework. The observed fluid pressure conditions demonstrate a clear regional difference between the southern and the north and north-eastern part of the study area. In the southern area, formation fluid pressures are close to normal and well below measured leak-off pressures. In the north, formation fluids are overpressured and may locally even approach the measured leak-off pressures. The regional differences in fluid overpressure can, in large part, be explained by differences in geologic framework and burial history. In the south, relatively low rates of sedimentary loading and the presence of relatively permeable sedimentary units have led to the currently observed normally pressured conditions. In the northern area, relatively rapid Neogene sediment loading plays an important role in explaining the observed overpressure distributions in Cenozoic mudstones, Cretaceous Chalk and Rijnland groups, and probably also in Jurassic units. The permeability framework of the northern and north-eastern area is significantly affected by Zechstein and Triassic salt deposits and structures. These units are characterised by very low permeability and severely restrict fluid flow and pressure dissipation. This has created hydraulically restricted compartments with high overpressures (for example overpressures exceeding 30 MPa in the Lower Germanic Trias Group in the Terschelling Basin and Dutch Central Graben).