PETROGENESA BATUAN INTRUSIF GUNUNG BERJO - BUTAK, DAERAH GODEAN BERDASARKAN DATA PETROGRAFINYA

KURVATEK ◽  
2018 ◽  
Vol 2 (1) ◽  
pp. 55-64
Author(s):  
Okki Verdiansyah
Keyword(s):  
Propylitic Alteration ◽  
Miarolitic Cavities ◽  
Subvolcanic Intrusion

Daerah Godean merupakan bagian dari vulkanisme Miosen, yang tersisa pada daerah Yogyakarta bagian tengah. Vukanisme pada daerah Godean, diperkirakan sebagai produk dari busur gunungapi kepulauan dengan diferensiasi yang terbentuk mulai dari andesit basaltik, andesit dasitik, dasit, riodasit, dan kembali menjadi andesit basaltik. Penelitian dilakukan pada batuan beku pada gunung Berjo, gunung Butak, batuan intrusi subvulkanik dengan orientasi sebaran selatan- timurlaut. Analisis data menggunakan petrografi sebanyak 17 sayatan tipis untuk melihat mineralogi dan tekstur khusus yang terdapat dalam batuan. Morfologi daerah penelitian berupa bukit terisolir dengan kelerengan 51 – 56 %, merupakan produk denudasional yang dikelilingi endapan kuarter dari fluvio-vulkanik gunung Merapi. Litologi pada gunung Berjo dan gunung Buthak terdiri dari andesit piroksen, dasit, andesit, basalt piroksen, yang merupakan batuan intrusi dangkal (subvolcanic intrusion) dengan tekstur utama berupa intersitial, mortar, porfiritik  yang diikuti tekstur khusus berupa oscilating zoning, sieve, dan miarolitic cavities terisi epidot-feldspar-kuarsa sebagai indikasi proses magmatic-hydrothermal pada suhu ± 200 - 400ºC diikuti alterasi hidrotermal berupa phyllic dan propylitic alteration yang terbentuk pada pH  4-5 dengan temperatur 200-3000C. Petrogenesa batuan gunung Berjo dan Butak diinterpretasi terbentuk sebagai batuan intrusi dangkal pada kedalaman 500 m dari permukaan purba, afinitas magma kapur alkali busur gunung api kepulauan dengan konten air tinggi, yang diikuti proses fraksinasi kristalisasi dengan pergerakan magma intrusi yang relatif melambat dan menerobos batuan sedimen karbonat. Petrogenesa daerah Godean masih perlu diperkuat dengan riset mineralogi lebih detil dan data lain yang mendukung.

scholarly journals The geology, petrology, and geochronology of the Archean Côté Gold large-tonnage, low-grade intrusion-related Au(–Cu) deposit, Swayze greenstone belt, Ontario, Canada

2017 ◽  
Vol 54 (2) ◽  
pp. 173-202 ◽  
Author(s):  
Laura R. Katz ◽  
Daniel J. Kontak ◽  
Benoît Dubé ◽  
Vicki McNicoll
Keyword(s):  
Greenstone Belt ◽  
Thermal Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Low Grade ◽  
Metavolcanic Rocks ◽  
Volcanogenic Massive Sulphide ◽  
Abitibi Subprovince ◽  
Back Arc ◽  
Miarolitic Cavities ◽  
Subvolcanic Intrusion

The Archean Côté Gold Au(–Cu) deposit is the first large gold deposit discovered in the Swayze greenstone belt of the Abitibi Subprovince. The deposit is a low-grade, large-tonnage type with a combined indicated and inferred resource of 8.65 M oz Au (245.2 t Au). The deposit is hosted by the Chester intrusive complex (CIC), a multiphase, subvolcanic intrusion composed of low-Al tonalite, diorite, and quartz diorite, plus magmatic and hydrothermal breccia bodies. The age of the tonalite and dioritic phases is constrained at 2741–2739 ± 1 Ma using high-precision isotope dilution – thermal ionization mass spectrometry (ID–TIMS) U–Pb zircon geochronology. Although these phases are co-temporal and co-spatial, they appear to be petrogenetically unrelated. The CIC was emplaced into mafic metavolcanic rocks of the Arbutus Formation whose geochemistry reflects a back-arc environment. The tonalite of the CIC is coeval and co-genetic with the felsic to intermediate metavolcanic rocks of the Yeo Formation. Emplacement of the CIC into a shallow crustal level is inferred based on the incorporation of screens and inclusions of the Yeo Formation and is supported by the presence of textures in tonalite and dioritic rocks (e.g., granophyres, miarolitic cavities, and pegmatites), as well as Al-in-hornblende geobarometry results of ≤1.3 ± 0.6 kbars (1 kbar = 100 MPa). The CIC is petrologically similar to other subvolcanic, low-Al tonalite–trondhjemite–diorite intrusions that underlie volcanogenic massive sulphide (VMS)-type deposits and which themselves may contain syn-intrusion mineralization. Several geochemically unrelated dykes and deformation events crosscut and postdate the CIC.

scholarly journals Crystal mush dykes as conduits for mineralising fluids in the Yerington porphyry copper district, Nevada

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Lawrence C. Carter ◽  
Ben J. Williamson ◽  
Simon R. Tapster ◽  
Catia Costa ◽  
Geoffrey W. Grime ◽  
...  
Keyword(s):  
Low Temperature ◽  
Cross Section ◽  
Porphyry Copper ◽  
Similar Type ◽  
Interconnected Network ◽  
Crystal Mush ◽  
Porphyry Deposit ◽  
Hydrothermal Quartz ◽  
Miarolitic Cavities

AbstractPorphyry-type deposits are the world’s main source of copper and molybdenum and provide a large proportion of gold and other metals. However, the mechanism by which mineralising fluids are extracted from source magmas and transported upwards into the ore-forming environment is not clearly understood. Here we use field, micro-textural and geochemical techniques to investigate field relationships and samples from a circa 8 km deep cross-section through the archetypal Yerington porphyry district, Nevada. We identify an interconnected network of relatively low-temperature hydrothermal quartz that is connected to mineralised miarolitic cavities within aplite dykes. We propose that porphyry-deposit-forming fluids migrated from evolved, more water-rich internal regions of the underlying Luhr Hill granite via these aplite dykes which contained a permeable magmatic crystal mush of feldspar and quartz. The textures we describe provide petrographic evidence for the transport of fluids through crystal mush dykes. We suggest that this process should be considered in future models for the formation of porphyry- and similar-type deposits.

scholarly journals Rapid alteration of fractured volcanic conduits beneath Mt Unzen

2021 ◽  
Vol 83 (5) ◽  
Author(s):  
Tim I. Yilmaz ◽  
Fabian B. Wadsworth ◽  
H. Albert Gilg ◽  
Kai-Uwe Hess ◽  
Jackie E. Kendrick ◽  
...  
Keyword(s):  
Country Rock ◽  
Geophysical Methods ◽  
Hydrothermal Fluids ◽  
Deep Drilling ◽  
Stress Regime ◽  
Argillic Alteration ◽  
Carbon And Oxygen Isotope ◽  
Propylitic Alteration ◽  
Indirect Information

AbstractThe nature of sub-volcanic alteration is usually only observable after erosion and exhumation at old inactive volcanoes, via geochemical changes in hydrothermal fluids sampled at the surface, via relatively low-resolution geophysical methods or can be inferred from erupted products. These methods are spatially or temporally removed from the real subsurface and thus provide only indirect information. In contrast, the ICDP deep drilling of the Mt Unzen volcano subsurface affords a snapshot into the in situ interaction between the dacitic dykes that fed dome-forming eruptions and the sub-volcanic hydrothermal system, where the most recent lava dome eruption occurred between 1990 and 1995. Here, we analyse drill core samples from hole USDP-4, constraining their degree and type of alteration. We identify and characterize two clay alteration stages: (1) an unusual argillic alteration infill of fractured or partially dissolved plagioclase and hornblende phenocryst domains with kaolinite and Reichweite 1 illite (70)-smectite and (2) propylitic alteration of amphibole and biotite phenocrysts with the fracture-hosted precipitation of chlorite, sulfide and carbonate minerals. These observations imply that the early clay-forming fluid was acidic and probably had a magmatic component, which is indicated for the fluids related to the second chlorite-carbonate stage by our stable carbon and oxygen isotope data. The porosity in the dyke samples is dominantly fracture-hosted, and fracture-filling mineralization is common, suggesting that the dykes were fractured during magma transport, emplacement and cooling, and that subsequent permeable circulation of hydrothermal fluids led to pore clogging and potential partial sealing of the pore network on a timescale of ~ 9 years from cessation of the last eruption. These observations, in concert with evidence that intermediate, crystal-bearing magmas are susceptible to fracturing during ascent and emplacement, lead us to suggest that arc volcanoes enclosed in highly fractured country rock are susceptible to rapid hydrothermal circulation and alteration, with implications for the development of fluid flow, mineralization, stress regime and volcanic edifice structural stability. We explore these possibilities in the context of alteration at other similar volcanoes.

Genesis of porphyry and plutonic mineralisation systems in metaluminous granitoids of the Grampian Terrane, Scotland

1994 ◽  
Vol 85 (3) ◽  
pp. 221-237 ◽  
Author(s):  
David Lowry ◽  
Adrian J. Boyce ◽  
Anthony E. Fallick ◽  
W. Edryd Stephens
Keyword(s):  
Source Region ◽  
Crustal Contamination ◽  
Magma Ascent ◽  
Magmatic Fluid ◽  
Magmatic System ◽  
Low Salinity ◽  
Deep Faults ◽  
Supergene Enrichment ◽  
Propylitic Alteration ◽  
O 10

AbstractMineralisation associated with Late Caledonian metaluminous granitoids in the Grampian Terrane has been investigated using stable isotope, fluid inclusion and mineralogical techniques.A porphyry-stock-related style of mineralisation in the Grampian Terrane is characterised by a stockwork of veinlets and disseminations in dacite prophyries, consisting of quartz, dolomite, sulphides and late calcite, and well-developed wallrock alteration dominated by zones of phyllic, sericitic and propylitic alteration. On the basis of δ34S (+0·4±l·0‰), δ13C (−5·7‰ to + l·4‰) and δ18O (+10·8‰ to +19·9‰) it is likely that initial mineralising components were orthomagmatic with an input of external fluids during the later parageneses. Fluids were saline, boiling (up to 560°C), deficient in CO2, and ore deposition took place at depths of less than 3 km.Plutonic-hosted mineralisation in appinites, diorites, tonalites and monzogranites is commonly represented by sporadic disseminations and occasional veins consisting of quartz, calcite and sulphides. Wallrock alteration is generally propylitic with phyllic vein selvages. Deposition from a cooling magma sourced fluid is indicated by δ34S (+2·6±l·5‰), δ13C (−7·2‰ to −4·5‰) and δ18O (+9·5‰ to + ll·8‰) data. Fluids were CO2-rich and of low salinity; inclusions were trapped below ≈460°C, and formed at estimated depths of 3–5 km.Differences between these styles of mineralisation may due to multiple factors, the most important being the nature of the fluid: porphyry systems are dominated by greater volumes and much higher temperatures of hydrothermal fluids. Other controlling factors are likely to be the compositional characteristics of the melt source region, the mechanism of magma ascent, the level of emplacement, and the nature of the host metasediments. Variations in δ34S between the two groups are related, for the most part, to redox processes during magma and fluid genesis and not by crustal contamination.Nolarge porphyry-related mineral deposits have been found in the Grampian Terrane, unlike those in Mesozoic and Tertiary continental margin environments. This is largely due to a combination of detrimental factors which massively reducesthe probability of economic mineralisation. These include the already metamorphosed nature of the host Dalradian, the absence of seawater (which entered many subduction-related magmatic systems), a poorly-developed system of deep faults (most deposits too deep to be influenced by surface-derived fluids), and the absence of supergene enrichment. The main processes which aid the concentration of mineralisation involve encroachment of external fluids (formation, meteoric and seawaters) into the magmatic system, but these fluids were largely absent from the Grampian host block at the time of granitoid intrusion.The results of this study can be used in characterising the sources of fluids in sedimentary-hosted ore veins known (or considered) to be underlain by metaluminous granitoid batholiths, particularly in estimating the degree of magmatic fluid inputs into the vein systems: an example where this interaction has occurred (the Tyndrum Fault Zone) is discussed.

scholarly journals Non-metamict betafite from Le Carcarelle (Vico volcanic complex, Italy): occurrence and crystal structure

2004 ◽  
Vol 68 (6) ◽  
pp. 939-950 ◽  
Author(s):  
F. Cámara ◽  
C. T. Williams ◽  
G. Della Ventura ◽  
R. Oberti ◽  
E. Caprilli
Keyword(s):  
Structure Refinement ◽  
Atomic Displacement ◽  
Campi Flegrei ◽  
Volcanic Complex ◽  
Crystal Chemical Formula ◽  
Static Disorder ◽  
Pyrochlore Group ◽  
Atomic Displacement Parameters ◽  
Miarolitic Cavities ◽  
Ti Content

AbstractNon-metamict betafite, a pyrochlore-group mineral with general formula A2−mB2XO6Y(O,OH,F)1−n·pH2O and 2 Ti > Nb+Ta and U > 20% at the A site, has been found at Le Carcarelle, (Latium, Italy). It occurs within miarolitic cavities of a foid-bearing syenitic ejectum enclosed within the pyroclastic formation known as “ignimbrite C”, which belongs to the main effusive phase of the Vico volcanic complex. The host rock is composed of K-feldspar, biotite, augitic clinopyroxene, magnetite and minor sodalite. Electron microprobe analyses gave the following crystal-chemical formula: (Ca1.24Na0.17U0.49REE0.03)Σ=1.93 (Ti1.05Nb0.76Zr0.14Fe0.04Ta0.01)Σ=2.00O6(O,OH). Compared with other occurrences reported in the mineralogical literature, betafite from Le Carcarelle is extremely enriched in U and depleted in Th. Due to its young age of formation (∼150 k.y.), this betafite sample is highly crystalline, thus allowing structure refinement of unheated material. Betafite from Le Carcarelle is cubic Fd3̅m, with a = 10.2637(13) Å, and V = 1081.21(35) Å3, and has a smaller A site (consistent with the higher U content), and a larger and more distorted B site (consistent with the higher Ti content) than calciobetafite from Campi Flegrei, Italy (Mazzi and Munno, 1983). Analysis of the atomic displacement parameters provides evidence for static disorder at the X site.

Element transport and enrichment during propylitic alteration in Paleozoic porphyry Cu mineralization systems: Insights from chlorite chemistry

2018 ◽  
Vol 102 ◽  
pp. 437-448 ◽  
Author(s):  
Bing Xiao ◽  
Huayong Chen ◽  
Pete Hollings ◽  
Yunfeng Wang ◽  
Juntao Yang ◽  
...  
Keyword(s):  
Porphyry Cu ◽  
Element Transport ◽  
Propylitic Alteration

Chlorite and Epidote Mineral Chemistry in Porphyry Ore Systems: A Case Study of the Northparkes District, New South Wales, Australia

2020 ◽  
Vol 115 (4) ◽  
pp. 701-727 ◽  
Author(s):  
Adam Pacey ◽  
Jamie J. Wilkinson ◽  
David R. Cooke
Keyword(s):  
New South ◽  
New South Wales ◽  
Mineral Chemistry ◽  
Ore Deposits ◽  
Low Grade ◽  
South Wales ◽  
Spatial Trends ◽  
Propylitic Alteration ◽  
Mineral Partitioning

Abstract Propylitic alteration, characterized by the occurrence of chlorite and epidote, is typically the most extensive and peripheral alteration facies developed around porphyry ore deposits. However, exploration within this alteration domain is particularly challenging, commonly owing to weak or nonexistent whole-rock geochemical gradients and the fact that similar assemblages can be developed in other geologic settings, particularly during low-grade metamorphism. We document and interpret systematic spatial trends in the chemistry of chlorite and epidote from propylitic alteration around the E48 and E26 porphyry Cu-Au deposits of the Northparkes district, New South Wales, Australia. These trends vary as a function of both distance from hydrothermal centers and alteration paragenesis. The spatial trends identified in porphyry-related chlorite and epidote at Northparkes include (1) a deposit-proximal increase in Ti, As, Sb, and V in epidote and Ti in chlorite, (2) a deposit-distal increase in Co and Li in chlorite and Ba in epidote, and (3) a pronounced halo around deposits in which Mn and Zn in chlorite, as well as Mn, Zn, Pb, and Mg in epidote, are elevated. Chlorite Al/Si ratios and epidote Al/Fe ratios may show behavior similar to that of Mn-Zn or may simply decrease outward, and V and Ni concentrations in chlorite are lowest in the peak Mn-Zn zone. In comparison to porphyry-related samples, chlorite from the regional metamorphic assemblage in the district contains far higher concentrations of Li, Ca, Ba, Pb, and Cu but much less Ti. Similarly, metamorphic epidote contains higher concentrations of Sr, Pb, As, and Sb but less Bi and Ti. These chlorite and epidote compositional trends are the net result of fluid-mineral partitioning under variable physicochemical conditions within a porphyry magmatic-hydrothermal system. They are most easily explained by the contribution of spent magmatic-derived ore fluid(s) into the propylitic domain. It is envisaged that such fluids experience progressive cooling and reduction in fs2 during outward infiltration into surrounding country rocks, with their pH controlled by the extent of rock-buffering experienced along the fluid pathway.

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