propylitic alteration

In particular, calcite is useful in buffering acid-water to more neutral pHs and precipitating metals held in solution. Propylitic alteration of volcanic rock can be subdivided into actinolite, epidote, and chlorite subzones. Depths below 1,200 m are known as a propylitic alteration zone since it's volume increased and there is a lot of crystalline epidote. The propylitic alteration zone represents the most distal signature of mineralisation, detectable kilometres away from the main orebody ( Cooke et al., 2014a) and, as such, is an important target for exploration. Minor minerals associated with propylitic alteration are calcite, sericite and pyrite. Figure 5: An example of Subaqueous Debris Flow unit from borehole image log (left) and petrography analysis (right). Often there is early development of a wide area of secondary biotite that gives the rock a distinctive brownish colour. Argillic alteration is characterized by montmorillonite, kaolinite and minor sericite and appears to be concetrated along joints Ideally, mineralized zones will have a central area with secondary biotite or potassium feldspar and outward 'shells' of cream or . propylitic alteration there have been separated the actinote zone (inner pro-pylitization) (Plate II, Fig. In the image-map, propylitic alteration zone (with high amounts of minerals containing Fe, Mg-OH) is observed in green color and phyllic alteration zone (with high . 6h-n). Phyllic, argillic, silicic and propylitic alteration zones were observed at the surface while potassic alteration zone could be observed at depth in drill core samples. Introduction Remote sensing is a method used in reconnaissance surveys. Mineralogical transitions across the propylitic zone are therefore repeated in the evolution from P1 to P3 veins, as well as in the halos around these veins. Hydrothermal alteration described at many occurrences exhibits zoning from proximal potassic alteration to typically peripheral and(or) later sericitic alteration, that is flanked by large zones of propylitic alteration. In the Comstock region the mineral maps show acid-sulfate alteration, widespread propylitic alteration and extensive faulting that offsets the acid-sulfate areas, in contrast to the larger, dominantly acid-sulfate alteration exposed along Geiger Grade. It comprises mainly chlorite and epidote, together with lesser quantities of clinozoisite, calcite, zoisite, and albite In places sericite, Fe-oxides, montomorillonite and zeolite may also be common. This method can periodically This evolution results from several local porosity modifications which occur at different scales in the rock: (1) at the core scale, from 10 to 10 m, where rock porosity changes as a function of rock-forming . 1. areas of propylitic alteration which is situated north of Curug Siliwangi, within the Malabar Caldera and the N-S trend of advanced argillic alteration zone that might be related with fractures. Hypogene mineralisation associated with porphyry-like veins (Fig. The study area is located in Iran central zone and Urumieh-Dokhtar volcanoplutonic belt. Farther outward, volcanic units have been affected by widespread and intense phyllic alteration and sericitization, and by the formation of quartz stockworks and up to 2-57a disseminated pydte. Parallel nicols at left and cross polarized at right. This process produces calcite, chlorite, epidote, and albite , which are greenschist facies minerals observed in unaltered rocks (calcite excepted). The K‐silicate assemblage includes sericite, rare chlorite, quartz, K‐feldspar and pyrite. sericitic alteration zone because of the existence of chlorite, clay minerals (probably illite), pyrite, and in some depths chalcopyrite and white muscowite. This pattern is similar to alteration envelopes that are associated with many other porphyry Cu-Mo deposits. A shell of magnetite-destructive phyllic alteration with very low susceptibility envelops the potassic zones. With this separation of alteration types, it is not necessary to code the alteration type explicitly in the data files themselves, so the alteration type is a characteristic of each whole package or layer. Definition of propylitization The result of low-pressure- low-medium temperature alteration around many hydrothermal orebodies. Argillic alteration is characterized as "advanced" or "intermediate" depending on how severely the minerals in the original host rock have been changed. alteration zones from the centre outward are potassic, phyllic, and propylitic. Parallel nicols at left and cross polarized at right. Feature depth variations in particular appear to represent a new finding in chlorite reflectance spectroscopy; however, the causes are not entirely clear and require further investigation. K-Nearest Neighbor . There is a wide range of alteration degrees - from partial to whole replacement of the primary minerals. Propylitic alteration results in the formation of the minerals chlorite, epidote, and actinolite. In the north, high-temperature phyllic alteration is associated with the intrusion complex (Chambefort et al., Four further holes were drilled to the north of Cerro Chiquitin, including CBA-RC-03 (240m), CBA-RC-04 (234m), CBA-RC-05 (240m) and CBA-RC-09 (216m), all of which cut peripheral hydrothermal alteration with quartz veinlets, pyrite and a transition to propylitic alteration with the presence of epidote. Amiraie, (1991) recognized potassic, phyllic, argillic, and propylitic alteration zones at Meiduk It typically results in epidote - chlorite - albite alteration and veining or fracture filling with the mineral assemblage along with pyrite . 3) is roughly coincident with a small supergene resource (inferred 28.1 Mt at 0.4 % Cu at 0.2 % cut-off grade). Figure 5: An example of Subaqueous Debris Flow unit from borehole image log (left) and petrography analysis (right). Parallel nicols at left and cross polarized at right. ": porphyry"copper"deposits.",." As part of the Northern NSW first-pass drill program, a total of twenty-seven holes comprised of 5,356 metres of drilling have now been . Argillic. (2011) showed that into three subzones which, in order of increasing distance outwards, it is possible to use spectral features of alunite in the advanced-argillic comprise: (1) actinolite ± epidote ± chlorite; (2) epidote + chlorite . To view an enhanced version of Figure 7, please visit: It is commonly seen in copper porphyry ore deposits in calc-alkaline rocks. It is readily distinguished from more argillized alteration types by the occurrence (commonly) of chlorite, epidote, smectite and carbonate (usually calcite), and may contain an amphibole such as actinolite. Claims cover 1,510 hectares. The propylitic alteration (epidosites, quartz- epidosites) is recognizable as two cyan colored areas on the KThU image and medium (red) on the K image 12. Also, different mineral zones within the intense acid-sulfate areas were mapped. Propylitic alteration is pervasive and represented mainly by chloritization of primary and secondary biotite and groundmass material in rock peripheral to the central potassic zone. There is Propylitic alteration is usually found in the outer zones of epithermal gold and copper porphyry deposits. propylitic alteration zones have the most reflection in Bands 4 and 5 on SWIR [13]. The band ratio (b7 + b9)/b8, corresponds to the propylitic alteration mineral index shown in green pixels; it shows a distribution more or less similar to the phyllic alteration mineral index and is generally related to the Upper Cryogenian volcano-sedimentary unit and the Lower Ouarzazate Group granite unit (Figure 4c). sic, argillic, phyllic, and propylitic, with distinct mineralogy and decreasing intensity of alteration developed away from the vein or pluton, respectively. Hole 21ODD-027 was collared in 25 m of laterite and saprolite, then cut several narrow intervals of sparse quartz-ankerite veining developed in weakly metamorphosed, propylitic-altered andesite . Potassic and intermediate argillic alterations are nearly contemporaneous with ore deposition. 1), situated in the central part of the porphyry quartz-micromonzodioritic stock and the propylitic epidote-chlorite zone, which is situated in the marginal part of the stock. Carbonatization and propylitic alteration of fragmental basaltic rocks, Quesnel River gold deposit, Central British Columbia. Chemical analyses indicate the following changes during pervasive alteration of igneous rocks: (1) addition of Si, K, H, S, and Cu, and loss of Fe 3+ and Ca during intense biotitization . However, propylitic alteration (chlorite + calcite + epidote ±wairakite ±actinolite, along with ±albite and ±illite) is the most common and most recent alteration present on most of our rocks. propylitic and following, in succession, by argillic, potassic and silicic. The propylitic alteration zone is still part of the larger porphyry system, which includes both the ore deposit itself, the underlying intrusions and the unmineralized wallrocks that have undergone hydrothermal alteration. a propylitic zone with the occurrence of secondary minerals such as epidote and chlorite. The porosity of a propylitized granite from Charroux (France), with no fractures or sealed fractures, inreases by more than four times from the unaltered (0.3%) to the altered rock (1.4%). km2 propylitic alteration zone (Fig. An actinolite subzone containing actinolite, epidote, chlorite, and calcite extends 250 m away from the secondary biotite zone. Parallel nicols at left and cross polarized at right. The reactions between the aqueous magmatic-hydrothermal fluids and host rocks during potassic alteration at El Salvador and Grasberg includes (i) reduction of SO 4 2− in the aqueous fluids due to oxidation of ferrous iron in mafic minerals and (ii) disproportionation of SO 2 in the fluids by elevated concentrations of Ca 2+ leached by the . Some porphyry deposits (e.g., Far South East, Philippines) Propylitic alteration is a common distal and weak alteration observed in porphyry systems. The propylitic alteration is best developed in the andesite and quartz latite lithologies due to higher amounts of Ca-, Mg-, and Fe-bearing igneous minerals Propylitic assemblage: an acid buffering assemblage of minerals including calcite, chlorite, and epidote, that are spectrally identified in the AVIRIS data. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data was used to identify alteration zones associated with Fe-Skarn mineralization in the Ravanj village, Markazi Province, Iran. Propylitic alteration is the main alteration in the study area and is widespread in the bottom levels and to the periphery of the deposit. propylitic alteration (right bottom). Figure 3. However, propylitic alteration can also be distinguished by high whole-rock δ 13 C values and carbon contents (−19.1 to −1.4‰ and up to 0.79 wt %, respectively) that result from the incorporation of magmatic CO 2 during the mineralizing events. From the decomposing of iron and magnesium containing minerals Maps Multiple Kilometre Scale...! Chlorite-Epidote altered with numerous quartz/carbonate/hematite veins with halos of epidote-feldspar alteration this method can map surface anomalies. 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