Antimony-Gold mineralization in Rates (Northern Portugal)

<p>In the Dúrico-Beirão mining district several paragenetic associations have been described in gold mineralizations, including Sb-Au. The objective of this research was the study of the Sb-Au mineralization in the Rates area, from field reconnaissance of the mineralized structures by soil sampling to the petrographic and mineralogical study of the parageneses associated with this gold mineralization, mined by the Romans.</p><p>The portable XRF was used to measure Sb and As in farms and forest soils. The observed Au-Sb-As anomalies in the Rates area must be linked to Lagoa Negra mine by the same north-western trend fault. Historical mining works have been identified both in Lagoa Negra and in Rates, where rock-chip sampling returned results up to 30 g/t Au from the Rates prospect.</p><p>Some rock samples from Rates were studied by geochemical and petrographic analyses and were analysed in detail by scanning electron microscopy. The results indicate that the paragenetic association in Rates is Sb-Au, with stibnite as primary Sb sulfide mineral, valentinite as alteration mineral, and gold in native and granular form.</p><p><strong>Acknowledgment</strong></p><p>The work was financial supported within the compass of the ERA-MIN/0005/2018—AUREOLE project, FEDER through operation POCI-01-0145-FEDER-007690 funded by the Programa Operacional Competitividade Internacionalização—COMPETE2020 and by National Funds through FCT within the ICT (reference UIDB/04683/2020).</p>

Study on Optimum Free-face Condition of Cutting Hard Rock with Tunnel Boring Machine Hob

To explore the rock-breaking characteristics of cutting hard rock under free-face condition by tunnel boring machine (TBM) hob and obtain the optimum free-face condition, the rock-breaking processes such as crack propagation, amount of micro crack and reaction force with penetration depth are first investigated based on discrete element simulation method. Then, the crack length, rock chip area, specific energy consumption etc. with different free-face spacing (S) and free-face height (H) are studied combined with rock-cutting simulation and experiment. The research results show that the formation of the rock chip under free-face condition by TBM hob is driven by tensile failure, and it exists an optimum free-face condition with the S of 80 mm and the H of 200 mm to promote main crack propagation and enhance the rock-cutting efficiency, which can provide a reference for the application of rock-breaking technology under the free-face.

PROSPECTS OF NEWLY DISCOVERED UGUR AREA IN THE NORTHWEST OF THE GEDABEY ORE DISTRICT (LESSER CAUCASUS, AZERBAIJAN)

The article describes Ugur exploration area located in Gedabey Ore District of the Lesser Caucasus in NW of Azerbaijan. Results of trenches and channels sampling on the surface, RC bore holes and summary of significant drill intercepts (>0.29 ppm Au) of Ugur Exploration area are presented. It has been established that The deposit is enlarged by highly gold-silver result of surface outcrop rock chip samples over an area of 2.5 kms North-South by 2 kms East-West, with the Reza gold deposit located in the central part. Out of metallic minerals crystalline hematite was observed. On surface intensive barite and barite-hematite vein and veinlets, also gossan zones were observed. The main mineralization zones have been sampled in three trenches at a distance up to 270 m by trenches #1, #2 and #3 and received positive results for gold and silver. Also there have taken approximately 550 samples from outcrop #1 and #2. On the main orebody at surface centre there occured secondary quartzites with vein-veinlets barite-hematite mineralization over which there remain accumulations of hydrous ferric oxides cementing breccias of quartz and quartzites. And in erosion parts "reddish mass" being oxidation product of stock and stockverk hematite ores were observed. Representing typical gossans, these accumulations by the data of trenches for thickness about 5-10 m contain gold 0.3-2.0 ppm and silver 1.0-15.0 ppm. Ten diamond drill holes, named UGDD 01-10 were drilled in the center part of the deposit. The drill holes were sampled mainly in 1 meter lengths from the top of the hole to the bottom. The core samples were marked and placed into standard boxes. Significant intervals of weighted averages greater than 0.29 ppm over down hole intervals of 1 metres or greater (>0.29 ppm Au and >0.9 m) are summarized in table 3 below. In conclusion, the outcropping alteration at the deposit is typical of the upper steam-heated levels of high-sulfidation epithermal (HSE) deposits, which in most mineralized systems of this type, may cap higher-grade gold mineralization which is hosted by underlying vuggy and oxide zones.

POTENSI ENDAPAN EMAS YANG BERASOSIASI DENGAN STRUKTUR GEOLOGI DAERAH LIO TIMUR FLORES NUSA TENGGARA TIMUR

Pulau Flores merupakan salah satu pulau di Indonesia yang kaya akan potensi bahan tambang termasuk emas. Secara umum, potensi pertambangan di Pulau Flores cukup besar yang meliputi berbagai jenis galian Golongan A, B dan C. Untuk jenis galian Golongan A (emas), baru merupakan perkiraan karena belum dilakukan penelitian secara seksama. Tujuan penelitian ini adalah mengutahui potensi endapan emas yang berasosiasi dengan struktur geologi. Metode yang digunakan berupa orientasi litologi dan struktur geologi, analisis XRF (<em>X - Ray Fluoroscence) </em>dari sampel RC <em>(Rock Chip)</em> dan SS <em>(Stream Sediment). </em>Hasil pemrosesan data geokimia batuan dari data XRF terdiri dari unsur utama, unsur jejak, dan unsur tanah jarang memperlihatkan prospek mineral logam yang relatif kecil dengan mineral Au yang berkisar antara &lt;0,005-0.011 ppm, yang cukup jauh dari nilai <em>cut off grade</em> Au. Sedangkan dari hasil orientasi litologi dan struktur geologi diduga model mineralisasinya adalah tipe <em>epithermal vein system. </em>Sistem ini dikontrol oleh struktur patahan dan kekar.

Identificación de las Mineralizaciones de Cobre Aflorantes en el Corregimiento de San José de Oriente, La Paz, Cesar

Al suroeste del corregimiento de San José de Oriente, en el sector conocido como La Lagunita, municipio de La Paz, departamento del Cesar, se realizaron estudios exploratorios de geología superficial en la formación La Quinta, permitiendo identificar afloramientosde las zonas mineralizadas y unidades litoestratigráficas presentes en la área. Se tomaron cuatro muestras entre la zona de contacto, roca, caja y mineral, mediante el método Rock Chip, de las cuales se envió una a análisis cualitativo mediante el estudio de difracción de rayos X y otra a un análisis cuantitativo mediante absorción atómica en los laboratorios de la Universidad Industrial de Santander, para determinar minerales asociados y el porcentaje de cobre presente en las manifestaciones.A partir de los resultados obtenidos con el análisis de difracción de rayos X, se identificaron los minerales constituyentes de las rocas tales como: Cuarzo SiO2, Albita Na(AlSi3O8), Clinocloro (Mg, Fe, Al)6 ((OH)8 (AL, Si)4 O10), Hematita Fe2O3, Ortoclasa KAl- Si3O8, Illita (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)], Glagolevita NaMg6[Si3AlO10](OH,O)8H2O, Malaquita (CuOH)2CO3 y mediante los resultados de absorción atómica se logró verificar la alta concentración de cobre-Cu de 1,45 %.

Numerical Study on Process of Breaking Rock with TBM Cutter in Different Cutting Orders

In order to research the effect of different cutting orders on breaking mechanism of TBM cutters for the rock without joints, this paper established the simulation models of breaking rock three TBM cutters in simultaneous and sequential orders, which is based on the 2D discrete element method. A series of numerical experiments were designed and the whole process of production and propagation of crack and rock breaking was successfully simulated. The simulation results showed that the cutter order determines the breaking mode, which is carefully analyzed: The chipping stress under the sequential order is higher than simultaneous way. The chips are formed by the side cracks under the two loading modes, while the shape of the rock chip are different. The distribution of the principal stress contour is almost symmetrical in different cutting order. Finally, conclusions and future work are summarized.