scholarly journals KANDUNGAN MINERAL DI PERAIRAN BINUANGEUN, LEBAK-BANTEN

2016 ◽  
Vol 12 (2) ◽  
pp. 79
Author(s):  
Udaya Kamiludin ◽  
Udaya Kamiludin
Keyword(s):  
River Sediments ◽  
Volcanic Rocks ◽  
Mineral Resources ◽  
Fine Sand ◽  
Source Rocks ◽  
Coarse Silt ◽  
Sand Beach ◽  
Offshore Area ◽  
Rock Fragments ◽  
Shell Fragments

Data dan informasi sumberdaya mineral terkait dengan batuan penyusunnya di daerah pantai dan lepas pantai masih terbatas. Untuk keberadaan sumberdaya mineral ini maka dilakukan identifikasi kandungan mineral dalam sedimen sebagai objek penelitian guna mengetahui jenis, persentase, distribusi dan perkiraan sumber batuannya. Metode penelitan meliputi pengambilan sampel sedimen, pemisahan konsentrat dulang, analisis mineragrafi butir, dan petrografi batuan. Ragam mineral di dalam endapan sedimennya terdiri dari kuarsa, magnetit, amfibol, ilmenit, felspar, glaukonit, apatit, piroksen, limonit, zirkon, fragmen batuan dan pecahan cangkang. Fraksi mineral yang dominan adalah fraksi pasir sangat halus dan lanau kasar. Secara lateral distribusi kuarsa, felspar dan piroksen relatif membesar ke arah endapan sedimen gisik pasir, tanggul gisik dan sedimen sungai dengan persentase tertinggi, masing-masing mencapai 49 %, 21 % dan 13 %. Sedangkan distribusi limonit dan zirkon membesar ke arah endapan sedimen gisik pasir dengan persentase tertinggi, masing-masing mencapai 5 % dan 2 %. Persentase tertinggi magnetit 17 %, ilmenit 23 %, apatit 3 %, fragmen batuan 51% dan pecahan cangkang 90 % umumnya terdapat dalam endapan sedimen permukaan dasar laut. Keterdapatan mineral utama dan tambahan ini diduga bersumber dari Batuan Gunungapi andesiti-basaltik, dan Formasi Batuan Sedimen berbahan volkanik. Sedangkan klastika biogeniknya bersumber dari batugamping terumbu. Hasil analisis petrogafi menunjukan bahwa fragmen batuannya memiliki kesesuaian dengan penyusun litologinya. Kata Kunci : Kandungan mineral, distribusi mineral, sumber batuan, Perairan Binuangeun. Data and information mineral resources related to rock forming mineral on shore and offshore area is still limited. For the existence of mineral resources is then to identify the content of the sediment as the object study in order to determine the type, percentage, distribution and estimation of rocks origin. The method includes sedimentary sampler, pan concentrates separation, grain mineragraphy analysis, and petrography rock. The mineral in the sediment consist of quartz, magnetite, amphibole, ilmenite, feldspar, glauconite, apatite, pyroxene, limonite, zircon, rock fragments and shell fragments. The minerals fractions are dominant in very fine sand and coarse silt. Laterally, the distribution of quartz, feldspar and pyroxene relatively increasing towards sand beach, berm and river sediments with the highest percentage, respectively reach 49 %, 21 % and 13 %. While, distribution of limonite and zircon are increasing toward sand beach with the highest percentage, respectively 5 % and 2 %. The highest percentage of magnetite (17 %), ilmenite (23 %), apatite (3 %), and rock fragments (51 %) and shell fragments of surfacially sediments (90 %). The occurrence of these main and accessory minerals is thought to be originated from andesitic-basaltic volcanic rocks and from volcanoclastic sediments whereas bioclastic sediments are from reefs limestone. The petrography analysis shows that their rock fragments are compatible with their rocks forming minerals. Keywords: The minerals content, mineral distribution, source rocks, and Binuangeun Waters.

A possible new hydrocarbon play, offshore central West Greenland

1998 ◽  
pp. 28-30
Author(s):  
Nina Skaarup ◽  
James A. Chalmers
Keyword(s):  
Seismic Data ◽  
Mineral Resources ◽  
Source Rocks ◽  
Bright Spot ◽  
Offshore Area ◽  
West Greenland ◽  
The Government ◽  
Structural Closure ◽  
Multichannel Seismic Data ◽  
Seismic Lines

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Skaarup, N., & Chalmers, J. A. (1998). A possible new hydrocarbon play, offshore central West Greenland. Geology of Greenland Survey Bulletin, 180, 28-30. https://doi.org/10.34194/ggub.v180.5082 _______________ The discovery of extensive seeps of crude oil onshore central West Greenland (Christiansen et al. 1992, 1994, 1995, 1996, 1997, 1998, this volume; Christiansen 1993) means that the central West Greenland area is now prospective for hydrocarbons in its own right. Analysis of the oils (Bojesen-Koefoed et al. in press) shows that their source rocks are probably nearby and, because the oils are found within the Lower Tertiary basalts, the source rocks must be below the basalts. It is therefore possible that in the offshore area oil could have migrated through the basalts and be trapped in overlying sediments. In the offshore area to the west of Disko and Nuussuaq (Fig. 1), Whittaker (1995, 1996) interpreted a few multichannel seismic lines acquired in 1990, together with some seismic data acquired by industry in the 1970s. He described a number of large rotated fault-blocks containing structural closures at top basalt level that could indicate leads capable of trapping hydrocarbons. In order to investigate Whittaker’s (1995, 1996) interpretation, in 1995 the Geological Survey of Greenland acquired 1960 km new multichannel seismic data (Fig. 1) using funds provided by the Government of Greenland, Minerals Office (now Bureau of Minerals and Petroleum) and the Danish State through the Mineral Resources Administration for Greenland. The data were acquired using the Danish Naval vessel Thetis which had been adapted to accommodate seismic equipment. The data acquired in 1995 have been integrated with the older data and an interpretation has been carried out of the structure of the top basalt reflection. This work shows a fault pattern in general agreement with that of Whittaker (1995, 1996), although there are differences in detail. In particular the largest structural closure reported by Whittaker (1995) has not been confirmed. Furthermore, one of Whittaker’s (1995) smaller leads seems to be larger than he had interpreted and may be associated with a DHI (direct hydrocarbon indicator) in the form of a ‘bright spot’.

scholarly journals KAITAN TIPOLOGI PANTAI DENGAN KEBERADAAN PASIR BESI DI PANTAI MUKOMUKO, BENGKULU

2016 ◽  
Vol 10 (2) ◽  
pp. 59
Author(s):  
Udaya Kamiludin ◽  
Yudi Darlan ◽  
Deny Setiady
Keyword(s):  
Volcanic Rocks ◽  
Relative Magnitude ◽  
Source Rocks ◽  
Frequency Content ◽  
Sand Beach ◽  
Basaltic Rocks ◽  
Basaltic Composition ◽  
Waves And Currents ◽  
Placer Deposits ◽  
Gravel Beach

Pasir besi merupakan salah satu potensi di sebagian kawasan pantai Indonesia yang erat kaitannya dengan keberadaan kondisi geologi batuan bersusunan andesitik-basaltik, oleh sebab itu salah satunya dipilih pantai Mukomuko sebagai objek penyelidikan. Pasir besi ini terakumulasi sebagai endapan alokhton dari hasil pelapukan dan erosi tanah yang diangkut oleh sungai dan diendapkan di pantai. Proses marin berupa abrasi dan akrasi terbentuk di sepanjang garis pantai oleh pemusatan gelombang dan arus sejajar pantai. Metode penyelidikan meliputi deskripsi kualitatif karakteristik pantai, penentuan posisi, pemercontohan sedimen, analisis megaskopis, dan pemisahan mineral bersifat magnetik dengan menggunakan magnet tangan disertai foto mikrograf. Tipologi pantai Mukomuko terdiri dari gisik berpasir (Sand beach) yang sebagian di atasnya ada bangunan dinding laut, dan gisik berkerikil (Gravel beach). Endapan pasir besi umumnya menempati gisik berpasir, baik pada muka pantai maupun pada tanggul gisiknya yang sebagian membentuk pematang pantai. Distribusi persentase magnetit (% Fe) sejajar pantai memiliki pola besaran relatif sama dengan kadar frekuensi yang berkisar antara 0 % - 10 %, anomali dijumpai secara setempat pada tanggul gisik dengan kisaran antara 30,07 % - 45,73 %. Berdasarkan klasifikasi cebakan plaser, genesa pasir besi terkonsentrasi oleh media cair yang bergerak sebagai jenis plaser pantai yang dipengaruhi oleh fluviatil. Keterdapatan pasir besi diduga berasal dari Formasi Hulusimpang yang dikorelasikan sebagai Andesit Tua, Batuan Gunungapi Kuarter dan lapisan konglomerat aneka bahan Formasi Bintunan yang bersusunan andesitik-basaltik. Kata Kunci : Karakteristik pantai, magnetit, plaser pantai, sumber batuan, pantai Mukomuko Bengkulu. Iron sand is one of the mineral potential in some coastal areas of Indonesia, which is related to the presence of andesitic-basaltic rocks, therefore Mukomuko coast is then selected as the object of investigation. The iron sand is accumulated as the alochton deposit as the product of the weathering and soil erosion transported by the river and it is accumulated on the beach. The abrasion and accretion processes are formed along the shoreline by waves and currents parallel to the coast. The methods of investigation include coastal characteristics mapping, positioning, sediment sampling, megascopic analysis, and magnetic separation of minerals by using a hand magnet with micrograph photo. The coastal characteristics of Mukomuko consist of gravel beach, and sand beach that some sea walls built on. Iron sand deposits generally occupy a sand beach, either on the beach face or on the berm which partially form the beach ridge. The distribution of magnetite parallel to the coast has the same relative magnitude patterns with the frequency content ranging from 0 % - 10 %, anomaly is found locally on the berm with the frequency content ranging between 30.07 % - 45, 73 %. Based on the classification of placer deposits, iron sand is concentrated in the formation of moving liquid media as placer beach types affected fluvial. The presence of iron sand supposed to be derived from the Hulusimpang Formation is correlated as Old Andesite, Quaternary Volcanic Rocks and conglomerate layers of different materials of andesitic-basaltic composition from Bintunan Formation. Keywords: Coastal Characteristics, magnetite, beach placer, source rocks; shore of Mukomuko, Bengkulu.

scholarly journals KARAKTERISTIK PASIR DI PANTAI DAN LEPAS PANTAI BINUANGEUN, LEBAK-BANTEN

2016 ◽  
Vol 11 (2) ◽  
pp. 79
Author(s):  
Udaya Kamiludin ◽  
Yudi Darlan
Keyword(s):  
Surface Sediment ◽  
Depositional Environment ◽  
Fine Particles ◽  
Fine Sand ◽  
Stream Sediment ◽  
Source Rocks ◽  
Sand Beach ◽  
Beach Sediment ◽  
Volcanic Origin ◽  
Sediment Types

Pasir merupakan sesuatu penomena yang menarik karena padanya tersimpan misteri bagaimana partikel itu terendapkan sesuai dengan lingkungannya, apakah merupakan pasir pada lingkungan marin, pantai atau sungai. Untuk mengetahui lingkungan pengendapan tersebut maka dilakukan identifikasi karakteristik pasirnya. Metoda penelitan meliputi pengambilan contoh, analisis besar butir, klasifikasi nomenklatur sedimen dan parameter statistik. Klasifikasi nomenklatur sedimen pada endapan sedimen permukaan dasar laut, gisik pasir, tanggul gisik dan endapan sungai aktif didapat pasir sebanyak, masing masing 19, 35, 15 dan 3 percontoh. Ke empat jenis endapan mempunyai ukuran butir rata-rata (mean) relatif seragam, yaitu pasir halus (2 Φ - 3 Φ). Begitu juga ukuran pasirnya berupa pasir halus dengan kurva distribusi persen berat fluktuatif. Perbedaan terlihat pada ukuran pasir sedimen permukaan dasar laut dan sedimen sungai aktif, selain pasir halus hadir pula pasir menengah (1 Φ - 2 Φ). Klasifikasi lingkungan pasir memperlihatkan bahwa ke empat endapan mempunyai kesesuaian lingkungan pengendapan disertai adanya muatan partikel yang mengkasar dan menghalus dengan bentuk kurtosis leptokurtik dan platikurtik monomodal. Sumber batuan asal sedimen diduga berasal dari hasil abrasi batugamping terumbu yang tersingkap di pantai bagian tengah daerah penelitian dan pengerjaan ulang batuan gunungapi dan batuan sedimen asal volkanik yang umum tersingkap di utara daerah penelitian. Kata Kunci : Sedimen permukaan dasar laut, gisik pasir, tanggul gisik, sedimen sungai aktif, lingkungan pengendapan pasir, sumber batuan. Sand sediment is something interesting phenomenon because the sand is stored in the mystery of how the sand particles sedimented according to the deposition environment, what is the sand that was deposited in marine, beach or river environment. The identification of sand sediment characteristic is used for the determination of depositional environment. Study methods include sediment sampling, grain size analysis of sediment, sediment nomenclature classification and computing the statistical parameters. Sediment nomenclature classification results on the seafloor surface sediment, sand beach sediment, berm sediment and active stream sediment derived as much sand sediment types, respectively 19, 35, 15 and 3 samples. The four types of sediment deposition that has mean is relatively uniform, which falls on the fine sand (Φ 2 - Φ 3). While the size of sand fall in the fine sand with fluctuating weight percent distribution curve. The difference was in the size of the sand on the sea floor sediments and active stream sediments, in addition to fine sand also present medium sand (Φ1 - Φ2). Sand environment classification showed that all four types of the sediments have suitability depositional environment be accompanied excess coarse and fine particles with curved kurtosis leptokurtic and platykurtic monomodal. Source rocks of the sediments probably derived from the abrasion of coralreef limestone exposed in the central coast of study area and rework volcanic rocks and sedimentary rocks of volcanic origin are commonly exposed in the northern of study area. Key words: Seafloor surface sediment, sand beach, berm, active stream sediment, sand depositional environment, source rocks.

XXII.—Silurian Greywackes in Peeblesshire

1955 ◽  
Vol 65 (3) ◽  
pp. 327-357 ◽  
Author(s):  
Ewart Kendall Walton
Keyword(s):  
Volcanic Rocks ◽  
Source Rocks ◽  
Turbidity Currents ◽  
Chemical Analyses ◽  
Rock Fragments ◽  
Intermediate Group ◽  
The Third ◽  
Sedimentary Structures ◽  
Land Mass

SynopsisSedimentary structures in the greywackes of Peeblesshire, including graded bedding, cross-lamination and load-cast structures, are described and their origin discussed.Petrographically the greywackes are poorly sorted sediments composed of a variety of minerals and rock fragments. The minerals include quartz, felspar, augite and horn-blende, mica and chlorite, while the dominant rock fragments are andesites, spilites, quartz-keratophyres and granites.Three groups of greywackes are recognized according to their mineralogy. The first, the Pyroxenous group, contains augite and hornblende. Rocks of the second group, the Intermediate group, are without these minerals, while the third group consists of rocks rich in garnet—the Garnetiferous group. These mineralogical differences are reflected in differences in the chemical analyses of the three groups. From consideration of the chemical and modal analyses it is suggested that differences in source rocks have influenced the composition of the greywackes more than variations in the intensity of alteration due to weathering and transport.It is concluded that the greywackes have been formed from the rapid erosion of a land mass largely covered by Ordovician volcanic rocks, but also with developments of lowgrade regionally metamorphosed rocks and others resembling Torridonian arkoses. Sedimentation features are due to accumulation controlled largely by the action of turbidity currents.

The Witwatersrand pyrites and metamorphism

1983 ◽  
Vol 47 (345) ◽  
pp. 473-479 ◽  
Author(s):  
D. K. Hallbauer ◽  
K. von Gehlen
Keyword(s):  
Trace Element ◽  
Fluid Inclusions ◽  
Depositional Environment ◽  
Volcanic Rocks ◽  
Source Rocks ◽  
Fine Grained ◽  
Mineral Inclusions ◽  
Ore Minerals ◽  
Hand Specimen

AbstractEvidence obtained from morphological and extensive trace element studies, and from the examination of mineral and fluid inclusions in Witwatersrand pyrites, shows three major types of pyrite: (i) detrital pyrite (rounded pyrite crystals transported into the depositional environment); (ii) synsedimentary pyrite (round and rounded aggregates of fine-grained pyrite formed within the depositional environmen); and (iii) authigenic pyrite (newly crystallized and/or recrystallized pyrite formed after deposition). The detrital grains contain mineral inclusions such as biotite, feldspar, apatite, zircon, sphene, and various ore minerals, and fluid inclusions with daughter minerals. Most of the inclusions are incompatible with an origin by sulphidization. Recrystallized authigenic pyrite occurs in large quantities but only in horizons or localities which have been subjected to higher temperatures during the intrusion or extrusion of younger volcanic rocks. Important additional findings are the often substantial amounts of pyrite and small amounts of particles of gold found in Archaean granites (Hallbauer, 1982) as possible source rocks for the Witwatersrand detritus. Large differences in Ag and Hg content between homogeneous single gold grains within a hand specimen indicate a lack of metamorphic homogenization. The influence of metamorphism on the Witwatersrand pyrites can therefore be described as only slight and generally negligible.

Petrography and geochemistry of the siliciclastic Araba Formation (Cambrian), east Sinai, Egypt: implications for provenance, tectonic setting and source weathering

2015 ◽  
Vol 154 (1) ◽  
pp. 1-23 ◽  
Author(s):  
HOSSAM A. TAWFIK ◽  
IBRAHIM M. GHANDOUR ◽  
WATARU MAEJIMA ◽  
JOHN S. ARMSTRONG-ALTRIN ◽  
ABDEL-MONEM T. ABDEL-HAMEED
Keyword(s):  
Tectonic Setting ◽  
Source Area ◽  
Xrd Analysis ◽  
Climatic Conditions ◽  
Source Rocks ◽  
Northern Margin ◽  
Rock Fragments ◽  
Geochemical Parameters ◽  
Clastic Sediments ◽  
Chemical Index

AbstractCombined petrographic and geochemical methods are utilized to investigate the provenance, tectonic setting, palaeo-weathering and climatic conditions of the Cambrian Araba clastic sediments of NE Egypt. The ~ 60 m thick Araba Formation consists predominantly of sandstone and mudstone interbedded with conglomerate. Petrographically the Araba sandstones are mostly sub-mature and classified as subarkoses with an average framework composition of Q80F14L6. The framework components are dominated by monocrystalline quartz with subordinate K-feldspar, together with volcanic and granitic rock fragments. XRD analysis demonstrated that clay minerals comprise mixed-layer illite/smectite (I/S), illite and smectite, with minor kaolinite. Diagenetic features of the sandstone include mechanical infiltration of clay, mechanical and chemical compaction, cementation, dissolution and replacement of feldspars by carbonate cements and clays. The modal composition and geochemical parameters (e.g. Cr/V, Y/Ni, Th/Co and Cr/Th ratios) of the sandstones and mudstones indicate that they were derived from felsic source rocks, probably from the crystalline basement of the northern fringe of the Arabian–Nubian Shield. The study reveals a collisional tectonic setting for the sediments of the Araba Formation. Palaeo-weathering indices such as the chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of the clastic sediments suggest that the source area was moderately chemically weathered. On the northern margin of Gondwana, early Palaeozoic weathering occurred under fluctuating climatic conditions.

COAL AS A SOURCE OF OIL AND GAS: A CASE STUDY FROM THE BASS BASIN, AUSTRALIA

2003 ◽  
Vol 43 (1) ◽  
pp. 117 ◽  
Author(s):  
C.J. Boreham ◽  
J.E. Blevin ◽  
A.P. Radlinski ◽  
K.R. Trigg
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Middle Eocene ◽  
Vitrinite Reflectance ◽  
Mineral Resources ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Gas Generation ◽  
Australian Context ◽  
Effective Source

Only a few published geochemical studies have demonstrated that coals have sourced significant volumes of oil, while none have clearly implicated coals in the Australian context. As part of a broader collaborative project with Mineral Resources Tasmania on the petroleum prospectivity of the Bass Basin, this geochemical study has yielded strong evidence that Paleocene–Eocene coals have sourced the oil and gas in the Yolla, Pelican and Cormorant accumulations in the Bass Basin.Potential oil-prone source rocks in the Bass Basin have Hydrogen Indices (HIs) greater than 300 mg HC/g TOC. The coals within the Early–Middle Eocene succession commonly have HIs up to 500 mg HC/g TOC, and are associated with disseminated organic matter in claystones that are more gas-prone with HIs generally less than 300 mg HC/g TOC. Maturity of the coals is sufficient for oil and gas generation, with vitrinite reflectance (VR) up to 1.8 % at the base of Pelican–5. Igneous intrusions, mainly within Paleocene, Oligocene and Miocene sediments, produced locally elevated maturity levels with VR up to 5%.The key events in the process of petroleum generation and migration from the effective coaly source rocks in the Bass Basin are:the onset of oil generation at a VR of 0.65% (e.g. 2,450 m in Pelican–5);the onset of oil expulsion (primary migration) at a VR of 0.75% (e.g. 2,700–3,200 m in the Bass Basin; 2,850 m in Pelican–5);the main oil window between VR of 0.75 and 0.95% (e.g. 2,850–3,300 m in Pelican–5); and;the main gas window at VR >1.2% (e.g. >3,650 m in Pelican–5).Oils in the Bass Basin form a single oil population, although biodegradation of the Cormorant oil has resulted in its statistical placement in a separate oil family from that of the Pelican and Yolla crudes. Oil-to-source correlations show that the Paleocene–Early Eocene coals are effective source rocks in the Bass Basin, in contrast to previous work, which favoured disseminated organic matter in claystone as the sole potential source kerogen. This result represents the first demonstrated case of significant oil from coal in the Australian context. Natural gases at White Ibis–1 and Yolla–2 are associated with the liquid hydrocarbons in their respective fields, although the former gas is generated from a more mature source rock.The application of the methodologies used in this study to other Australian sedimentary basins where commercial oil is thought to be sourced from coaly kerogens (e.g. Bowen, Cooper and Gippsland basins) may further implicate coal as an effective source rock for oil.

Dynamic Interactions Between the Vadose and Phreatic Zones During Breaking Solitary Wave Runup and Drawdown Over a Fine Sand Beach

2009 ◽  
Author(s):  
Heng Xiao ◽  
Yin L. Young ◽  
Jean H. Pre´vost
Keyword(s):  
Porous Media ◽  
Solitary Wave ◽  
Fluid Pressure ◽  
Fine Sand ◽  
Laboratory Scale ◽  
Slope Instability ◽  
Multiphase Model ◽  
Wave Runup ◽  
Sand Beach ◽  
Dynamic Interactions

The objective of this work is to investigate the dynamic interactions between the vadose and the phreatic zones during breaking solitary wave runup and drawdown over a fine sand beach. Extreme wave runup and drawdown in the nearshore region can lead to soil failure in the form of severe erosion, liquefaction, or slope instability. However, the physics of the nearshore region is difficult to simulate numerically due to the greatly varying time scales between the four governing processes: loading and unloading caused by wave runup and drawdown, propagation of the saturation front, pore pressure diffusion, and soil consolidation. Such processes are also difficult to simulate experimentally via model-scale wave tank studies due to the inability to satisfy all the similarity requirements for both the wave and the porous media in a 1g environment. Hence, the goal of this work is to perform a 1D study using a multiphase model to describe the transient responses of the species saturation, pore fluid pressure, effective stresses, and skeleton deformation. Results are shown for three simulations: (1) full-scale simulation, (2) 1:20 laboratory-scale simulation without scaling of the porous media, and (3) 1:20 laboratory-scale with consistent scaling of the soil permeability. The results suggest that the scaling of porous media between the pore fluids and soil skeleton has a significant influence on the transient response of both the vadose and the phreatic zones.

scholarly journals Chapter 10 Mineral resources and prospectivity of the ultramafic rocks of New Caledonia

2020 ◽  
Vol 51 (1) ◽  
pp. 247-277 ◽  
Author(s):  
P. Maurizot ◽  
B. Sevin ◽  
S. Lesimple ◽  
L. Bailly ◽  
M. Iseppi ◽  
...  
Keyword(s):  
Genetic Model ◽  
New Caledonia ◽  
Mineral Resources ◽  
Ultramafic Rocks ◽  
Uppermost Mantle ◽  
Sand Beach ◽  
The Past ◽  
Metallic Mineral ◽  
Geomorphological Evolution ◽  
Podiform Chromitite

AbstractThe main metallic mineral resources of New Caledonia are hosted by the obducted Peridotite Nappe. Ni, Co, Cr and the Pt group elements (PGEs) are specific to this ultramafic terrane. Cr, as podiform chromitite in the uppermost mantle, is the only hypogene metal mined economically in the past. The largest chromitite deposits are located in the lherzolitic Tiébaghi Massif. Supergene Ni and Co deposits are concentrated by the tropical climate that has prevailed since the Miocene. New Caledonian lateritic Ni deposits account for 10% of the global Ni resources. Hydrous Mg silicate and oxide types coexist in a single deposit. A local genetic model based on geomorphological evolution is proposed. Sc is a prospective resource associated with these supergene deposits. The PGEs are a prospective resource associated with chromite, with potential in the hypogene, supergene and fluvio-littoral domains. Pt and Pd are the most significant elements. The transition zone between the upper mantle and crustal cumulates constitutes a regional Pt–Pd-enriched horizon. The concentrations are related to small disseminated chromite lenses in a pyroxene-rich lithology. The PGEs are concentrated in weathering profiles. The value of chromite-rich sands as placers or sand beach deposits might be enhanced by the occurrences of PGEs.

Pre-Acadian copper mineralization in the English Lake District

1999 ◽  
Vol 136 (2) ◽  
pp. 159-176 ◽  
Author(s):  
D. MILLWARD ◽  
B. BEDDOE-STEPHENS ◽  
B. YOUNG
Keyword(s):  
Quartz Crystal ◽  
Volcanic Rocks ◽  
Wall Rock ◽  
Lake District ◽  
Early Devonian ◽  
Rock Fragments ◽  
Copper Mineralization ◽  
English Lake District ◽  
Fibre Strain ◽  
Devonian Age

The Ordovician sedimentary and igneous rocks of the English Lake District host a widespread suite of epigenetic metalliferous veins dominated by copper sulphides with abundant arsenopyrite, pyrite and accessory galena and sphalerite. New field and microstructural evidence from examples of this suite at Coniston, Wasdale, Honister, Newlands and Borrowdale shows that the veins were strongly cleaved during the Early Devonian (Emsian) Acadian orogenic event. The principal evidence includes the continuity of wall-rock cleavage fabrics with pressure solution seams in the veins and consistently orientated cleavage through enclosed, rotated wall-rock fragments and chloritic mats. There is also widespread complex intracrystalline deformation in quartz, cataclasis of arsenopyrite and pyrite, fracturing and/or buckling of bladed hematite, and growth of quartz or mica-fibre strain fringes. Chalcopyrite was partially or totally remobilized, enabling it to migrate along quartz crystal boundaries, and invade brecciated pyrite. Previous K–Ar Early Devonian age determinations for the mineralization are considered to have been reset. The pre-Acadian age of this mineralization, its style and relationship to the volcanic rocks permits a genetic link with the final phases of Caradoc magmatism.

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