458 research outputs found
KAJIAN TEKNIS KESTABILAN STOPE PADA RENCANA PENAMBANGAN STOPE BG2540 XC 17 – 14 DAN BG2560 XC 37 – 14 TAMBANG BAWAH TANAH BIG GOSSAN PT.FREEPORT INDONESIA
No full textTambang bawah tanah Big Gossan PT.Freeport Indonesia, merupakan tambang bawah tanah yang menggunakan metode sublevel stoping dan paste filling. Permuka kerja pada tambang Big Gossan berupa stope dengan dimensi yang cukup besar dan tanpa menggunakan penyangga.Rencana penambangan akan dilakukan pada stope BG2540 xc 17 – 14 dan BG2560 xc 37 – 14. Pada stope ini belum dilakukan analisa kondisi kesetabilannya. Sebelum dilakukan penambangan perlu adanya analisa kestabilan pada stope.Analisa yang dilakukan meliputi kestabilan stope menggunakan grafik kestabilan Matthew, perpotongan bidang lemah menggunakan alat bantu program Roscience UNWEDGE, prediksi overbreak pada stope dan dilakukan penyesuaian grafik kestabilan dengan kondisi tambang Big Gossan level 2540 – 2560. Dari analisa grafik kestabilan Matthew, stope BG2540 xc 17 – 14 dalam kondisi unsupported transition zone pada sisi hanging wall 1 dan sisi lainnya dalam kondisi stabil, potensi perpotongan bidang lemah pada hanging wall 1 dengan volume 35,5 m3, bobot 106,8 ton, prediksi overbreak terbesar pada sisi hanging wall 1 sebesar 1,7 m. BG2560 xc 37 – 14 dalam kondisi stabil pada seluruh sisinya, potensi perpotongan bidang lemah pada side wall kanan dengan volume 42,89 m3, bobot 8,5 ton, prediksi overbreak terbesar pada sisi side wall kanan sebesar 0,7 m.Berdasarkan grafik yang telah disesuaikan stope BG2540 xc 17 – 14 dan BG2560 xc 37 – 14 dalam kondisi stabil. Grafik kestabilan yang telah disesuaikan dengan kondisi tambang Big Gossan level 2540 – 2560 dapat digunakan sebagai acuan penentuan kondisi kestabilan stope pada tambang Big Gossan level 2540 – 2560.Kata Kunci: Stope, Kestabilan, Overbrea
PENENTUAN AKUIFER BERDASARKAN ANALISIS HIDROKIMIA AIRTANAH DAN PENGARUH KONDISI GEOLOGI PADA AREA TAMBANG BAWAH TANAH (UNDER GROUND) BIG GOSSAN, PAPUA
No full textArea Tambang Bawah Tanah Big Gossan, PT Freeport Indonesia (PTFI) dengan posisi
kordinat 733250–734250 Easthing; 951250–952250 Northing Zona UTM 53 S. Terletak di
Pegunungan Jayawijaya, Kecamatan Mimika Timur, Kabupaten Mimika, Propinsi Papua.
Tambang Big Gossan terdiri dari beberapa formasi batuan yang batuan penyusun setiap formasi
berbeda. Selain itu pada tambang Big Gossan terdiri dari beberapa tipe alterasi dan mineralisasi.
Dari faktor tersebut, maka akan memungkinkan terjadinya perubahan kimia air pada daerah
tangkapan (recharge area) dan conto airtanah yang berada pada level 2540 m , karena pada saat
air bergerak melalui pori-pori atau rekahan dalam batuan maka akan terjadi proses pelarutan
mineral- mineral yang ada pada batuan yang dilewatinya.
Geologi area Tambang Bawah Tanah Big Gossan terdiri dari Formasi Ekmai yang
berumur kapur akhir, Formasi Waripi berumur Paleosen – Eosen Awal, dan intrusi diorite
Ertsberg yang berumur paleosen dengan litologi batuan dari tua ke muda adalah batupasir,
batugamping, hornfels, dolomit dan intrusi diorit. Berdasarkan analisa struktur kekar didapati
arah umum kekar tertutup (shear fracture) N 271 ˚E – N 270 ˚E dan arah umum kekar terbuka
(gash fracture) N 173 ˚ - N 179 ˚E E, tegasan utamanya berarah Tenggara – Barat Laut dengan
jenis sesar adalah sesar kiri turun (Normal left slip fault). Jenis alterasi pada area penelitian
termasuk dalam jenis alterasi Skarn. Zonasi skarn diendapan Big Gossan secara berturut-turut
dari batas hornfels (Kkeh) sampai kearah marmer/dolomit menjadi zona garnet + piroksen skarn
dan piroksen + garnet skarn.
Penentuan akuifer pada area penelitian dilakukan dengan metode diagram stiff dan
trilinear piper, water intersect, dan diagram schoeller didapati 2 tipe akuifer, yaitu akuifer kontak
Kkel-exoskarn Waripi dengan tipe Ca-SO4 dan Ca-Mg-SO4 dan dolomi Waripi dengan tipe Ca-
Mg-SO4-HCO3, kedua akuifer tersebut masuk kedalam jenis akuifer rekahan.
Jenis airtanah area Big Gossan berdasarkan asal dan proses terjadinya adalah air meteorik
berupa air hujan dan berdasarkan tempat terdapatnya airtanah yaitu air rekahan. Air yang keluar
berasal dari air hujan dapat dibuktikan dengan perbandingan nilai kimia antara air hujan dan
airtanah (Ph dan EC), selain itu dari hasil tracer test menunjukkan bahwa perjalan dye dari
permukaan sampai pada 2540/L hanya membutuhkan waktu 74 jam, dari sini kemungkinan
besar airtanah pada tambang Big Gossan merupakan air hujan.
Analisa geokimia batuan terhadap perubahan kimia airtanah terdapat dua (2) litologi
batuan yang mempunyai peranan penting, yaitu litologi batuan karbonat dan alterasi Waripi
skarn. Litologi batuan kerbonat berpengaruh terhadap jumlah kation – anion terlarut (Ca, Mg dan
HCO3) sedangkan untuk Waripi skarn berpengaruh terhadap nilai kandungan SO4 dan Ca yang
berasal dari mineral anhidrit dan piroksen, serta nilai kandungan mineral logam berupa Fe dan
Cu yang berasal dari mineral pirit dan kalkopiri
Jarosite: A silver bearing mineral of the gossan of Rio Tinto (Huelva) and La Union (Cartagena, Spain)
No full textThe mineralogy of the gossans of Rio Tinto and La Unión is studied. Special emphasis has been paid to the occurrence of jarosite group minerals because they constitute silver bearing material of technical importance. After granulometric separation of the fractions, magnetic separation was used to concentrate the jarosite-group minerals. Plumbojarosite, natrojarosite and argentojarosite were identified by X-ray diffraction techniques. The spatial deposition of jarosite, goethite and hematites has been studied in different samples and the sequence interpreted on the basis of the known literature. The silver content, as determined by SEM, indicates abundant silver deposition in an early phase of gossanization. The recovery in the industrial plant has been analyzed comparing the mineralogy of the whole one and the residues of flotation. This study reveals that the industrial process used today leaves unaltered the proportion of the jarosite minerals entering and leaving the plant.En este trabajo se estudia la mineralogía del gossan de Rio Tinto y La Unión. Se hace enfasis especial en los minerales del grupo de la jarosita, por ser los principales portadores de plata y de importancia técnica. Para concentrar los minerales de la jarosita se realizó una separación magnética previa. Plumbojarosita, natrojarosita y argentojarosita se identificaron mediante difracción de rayos X. Se ha estudiado la deposición espacial de jarosita, goethita y hematites y se ha interpratado sus secuencias en base a la bibliografía que se conoce. La distribución del contenido en plata, realizada mediante S. E. M. a puesto de manifiesto que la deposición de plata es más abundante en la primera fase de gossanización. La recuperación de la plata en la planta industrial ha sido analizada comparando la mineralogía del todo uno y del residuo del proceso de flotación. En general el proceso de flotación no concentra la plata quedando practicamente inalterada la proporción de minerales de la jarosita que entran y salen de la planta de tratamiento.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu
Salt glands enable salt but not metal(loid)s excretion in Limonium daveaui under amended saline and contaminated soils
No full textSoil–plant interactions are essential for understanding adaptive responses to abiotic stressors such as salinity and metal(loid)s contamination. This study analyzed plant behavior of the recretohalophyte Limonium daveaui Erben when cultivated in saline and in gossan mine soils, both with and without organic–inorganic amendments. Analysis included soil physicochemical and biological parameters, multielemental composition of plant tissues, and the cationic profile of salts excreted by foliar salt glands. All plants grown in unamended gossan soil died, whereas amendment addition substantially improved both gossan and saline Fluvisol properties, raising pH in gossan soil, reducing salinity, increasing nutrient availability, generally stimulating microbial enzymatic activity, thereby allowing normal plant development. In amended gossan soil, plants accumulated high concentrations of As and Pb and moderate levels of other potentially hazardous elements (PHE) in roots and shoots without visible toxicity symptoms. Transfer coefficients revealed low PHE translocation but high biological absorption, indicating efficient uptake. Microscopic analyses showed the presence of the typical Limonium salt glands on both leaf surfaces through which plants excreted salts with macroelements but not As and Pb. The findings indicate that plant's primary tolerance strategy is based on accumulation of metal(loi)s in roots, rather than exclusion or excretion through foliar salt glands.Open access funding provided by FCT|FCCN (b-on). This work was supported by FCT—Fundação para a Ciência e Tecnologia, I.P. through project reference UID/04129/2025. Antonio Aguilar-Garrido (AA-G) thanks the SPANISH MINISTRY OF SCIENCE, INNOVATION AND UNIVERSITIES for its predoctoral fellowship and the mobility grant under application references FPU-18/02901 and EST21/00734, respectively
The Archean Cu-Zn magnetite-rich Gossan Hill VHMS deposit, Western Australia : evidence of a structurally-focussed, exhalative and sub-seafloor replacement mineralising system
No full textThe Archean Cu-Zn Gossan Hill volcanic-hosted massive sulphide deposit is situated on the northeast flank of the Warriedar Fold Belt in the Yilgarn Craton, Western Australia. The deposit is hosted within re-deposited rhyodacitic tuffaceous volcaniclastics of the Golden Grove Formation and is overlain by rhyodacite-dacite lavas and intrusive domes of the Scuddles Formation. The Gossan Hill deposit consists of two discrete subvertical ore zones situated stratigraphically 150 m apart in the middle and upper Golden Grove Formation. The stratigraphically lower Cu-rich ore zone (7.0 Mt @ 3.4% Cu) consists of stratabound, podiform to discordant massive pyrite-chalcopyrite-pyrrhotite-magnetite. In addition to massive sulphides, the lower ore zone also contains discordant to sheet-like zones of massive magnetite-carbonate-chlorite-talc (~12 Mt). The upper Zn-Cu ore zone (2.2 Mt @ 11.3% Zn, 0.3% Cu, 15 g/t Au and 102 g/t Ag) is mound-shaped with sheet-like, stratabound, massive sphalerite-pyrite-chalcopyrite overlying discordant massive pyrite-pyrrhotite-chalcopyrite-magnetite. A sulphide-rich vein stockwork connects the upper and lower ore zones. Metal zonation grades from Cu-Fe (¬¨¬±Au) in the lower ore zone to Zn-Cu-rich sulphides at the base of the upper ore zone. The upper ore zone grades upwards and laterally from Zn-Cu to Zn-Ag-Au (¬¨¬±Cu, ¬¨¬±Pb)-rich sulphides. Regional preservation of primary tuffaceous volcanic textures within the Golden Grove Formation is attributed to an early syndepositional, quartz-chlorite alteration. Induration and differential permeability/porosity reduction of the succession during the early alteration likely promoted more-focussed pathways for successive hydrothermal fluids. Subsequent hydrothermal alteration related to mineralisation at Gossan Hill has a limited lateral extent, and forms a narrow Fe-chlorite-ankerite-siderite envelope to the massive magnetite and sulphide of the lower ore zone, and an intense siliceous envelope surrounding the stockwork and upper ore position. Pervasive calcite-muscovite alteration is recognised in the hangingwall volcanics of the Scuddles Formation. The nature of deformation and metamorphism (greenschist facies: 454 ¬¨¬±4¬¨‚àûC at 1 kbar based on andalusite-chloritoid-quartz equilibrium) is uniform throughout the massive magnetite, massive sulphide and host succession. Sediment-sulphide-magnetite relationships at Gossan Hill suggest the formation of magnetite and sulphide during deposition of the upper Golden Grove Formation. Massive magnetite formed entirely by sub-seafloor replacement processes as inferred from gradational upper and lower contacts and interdigitating volcaniclastics. Replacement occurred along permeable tuffaceous strata outward from a discordant feeder. Massive magnetite was later veined, replaced and cut by massive sulphide. The synchronous formation of both upper and lower sulphide ore zones is indicated by the connecting sulphide stockwork. Both sulphide ore zones formed by sub-seafloor replacement, although stratiform hydrothermal chert-sulphide-sediment layers in, and adjacent to, the upper sulphide zone attest to some exhalation of fluids onto the seafloor. The thickest occurrence of massive magnetite, massive sulphide and stringer stockwork spatially coincide and support a common feeder conduit during massive magnetite and sulphide mineralisation. The asymmetry of hydrothermal alteration envelopes, massive magnetite and massive and veins sulphide zones are consistent with synvolcanic structural controls, with a growth structure occupied and obscured by a younger dacite dome from the Scuddles Formation. A systematic increase in sulphide ˜í¬•\^{34}\S values (range of -4.0 to 7.8‚ÄövÑ‚àû, average 2.1 ¬¨¬± 1.7‚ÄövÑ‚àû) stratigraphically upwards through massive and vein sulphide is suggestive of progressive mixing of upwelling ore fluids with entrained seawater. Homogeneous ˜í¬•\^{34}\S values of ~1.5‚ÄövÑ‚àû in the lower ore zone have a consistent homogeneous rock sulphur source with possible magmatic contributions. The ˜í¬•\^{18}\O\_{H20}\ values of ore fluids responsible for deposition of magnetite in massive magnetite and disseminated magnetite in the sulphide zones range from 6% to 13%. This data is inconsistent with the direct input of Archean seawater, and favours derivation of hydrothermal fluids by rock buffering of circulating fluids, or by direct magmatic contribution. Thermodynamic considerations suggest massive magnetite and sulphide formed from high temperature (300¬¨‚àû to 350¬¨‚àûC), reduced (low `f` O\_2\, slightly acidic hydrothermal fluids. H\_2\S deficient fluids formed massive magnetite, whilst H\_2\S-rich fluids formed massive sulphides. Fluid chemistry differences are attributed to magmatic sulphur contributions during sulphide mineralisation. Precipitation of sub-seafloor sulphide in the lower ore zone resulted from chemical entrapment by the interaction of upwelling H\_2\S-rich fluids with pre-existing massive magnetite. It is suggested that shallow parental magma chambers to the Scuddles Formation drove hydrothermal convection of seawater and may have supplied volatiles and H\_2\S to the ascending hydrothermal fluids. The Gossan Hill sulphide-magnetite deposit represents an evolving hydrothermal system in an environment characterised by rapid volcaniclastic sedimentation and changing structural and magmatic processes. An important influence on this hydrothermal system was the creation and destruction of porosity and permeability in the host succession. The hydrothermal system initiated as part of a regional seawater convection-alteration system that led to VHMS mineralisation at Gossan Hill by (1) synsedimentary metasomatism and progressive heating of convecting fluids, (2) formation of massive magnetite by host rock replacement above a buried synvolcanic conduit, and (3) structural re-activation and tapping of deeper H\_2\S-rich and metal-bearing fluids, leading to the sub-seafloor sulphide replacement and local exhalation of hydrothermal fluids forming sulphide and chert. Burial by proximal felsic volcanism led to preservation of the deposit
The Potential of Cistus salviifolius L. to Phytostabilize Gossan Mine Wastes Amended with Ash and Organic Residues
No full textThe São Domingos mine is within the Iberian Pyrite Belt, a mining district with large concentrations of polymetallic massive sulfide deposits. Mine waste heaps are considered extreme environments, since they contain high total concentrations of potentially hazardous elements (PHE), which contribute to inhibiting the development of most plants. Autochthonous plant species, such as Cistus salviifolius L., are able to grow naturally in this degraded environment, and may contribute to minimizing the negative chemical impacts and improving the landscape quality. However, the environmental rehabilitation processes associated with the development of these plants (phytostabilization) are very slow, so the use of materials/wastes to improve some physicochemical properties of the matrix is necessary in order to speed up the process. This work studied the effectiveness of the phytostabilization with C. salviifolius of gossan mine wastes from the mine of São Domingos amended with organic and inorganic wastes in order to construct Technosols. The mine wastes have an acid pH (≈3.5), high total concentrations of PHE and low concentrations of organic C and available nutrients. The best vegetative development occurred without visible signs of toxicity in the Technosols containing a mixture of agriculture residues. These treatments allowed the improvement of the soil-plant system providing a better plant cover and improved several chemical properties of mine wastes, helping to speed up the environmental rehabilitation
The Potential of Cistus salviifolius L. to Phytostabilize Gossan Mine Wastes Amended with Ash and Organic Residues
No full textThe São Domingos mine is within the Iberian Pyrite Belt, a mining district with large
concentrations of polymetallic massive sulfide deposits. Mine waste heaps are considered extreme
environments, since they contain high total concentrations of potentially hazardous elements (PHE),
which contribute to inhibiting the development of most plants. Autochthonous plant species, such as
Cistus salviifolius L., are able to grow naturally in this degraded environment, and may contribute
to minimizing the negative chemical impacts and improving the landscape quality. However, the
environmental rehabilitation processes associated with the development of these plants (phytostabilization)
are very slow, so the use of materials/wastes to improve some physicochemical properties
of the matrix is necessary in order to speed up the process. This work studied the effectiveness
of the phytostabilization with C. salviifolius of gossan mine wastes from the mine of São Domingos
amended with organic and inorganic wastes in order to construct Technosols. The mine wastes
have an acid pH ( 3.5), high total concentrations of PHE and low concentrations of organic C and
available nutrients. The best vegetative development occurred without visible signs of toxicity in the
Technosols containing a mixture of agriculture residues. These treatments allowed the improvement
of the soil-plant system providing a better plant cover and improved several chemical properties of
mine wastes, helping to speed up the environmental rehabilitationinfo:eu-repo/semantics/publishedVersio
The Potential of Cistus salviifolius L. to Phytostabilize Gossan Mine Wastes Amended with Ash and Organic Residues
No full textThe São Domingos mine is within the Iberian Pyrite Belt, a mining district with large
concentrations of polymetallic massive sulfide deposits. Mine waste heaps are considered extreme
environments, since they contain high total concentrations of potentially hazardous elements (PHE),
which contribute to inhibiting the development of most plants. Autochthonous plant species, such as
Cistus salviifolius L., are able to grow naturally in this degraded environment, and may contribute
to minimizing the negative chemical impacts and improving the landscape quality. However, the
environmental rehabilitation processes associated with the development of these plants (phytostabilization)
are very slow, so the use of materials/wastes to improve some physicochemical properties
of the matrix is necessary in order to speed up the process. This work studied the effectiveness
of the phytostabilization with C. salviifolius of gossan mine wastes from the mine of São Domingos
amended with organic and inorganic wastes in order to construct Technosols. The mine wastes
have an acid pH ( 3.5), high total concentrations of PHE and low concentrations of organic C and
available nutrients. The best vegetative development occurred without visible signs of toxicity in the
Technosols containing a mixture of agriculture residues. These treatments allowed the improvement
of the soil-plant system providing a better plant cover and improved several chemical properties of
mine wastes, helping to speed up the environmental rehabilitationinfo:eu-repo/semantics/publishedVersio
KAJIAN DAMPAK TEKNIS PELEDAKAN BAWAH TANAH DI STOPE 38 LEVEL 3060 BIG GOSSAN MINE PT FREEPORT INDONESIA PROVINSI PAPUA
No full textKegiatan development yang dilakukan pada tambang Big Gossan meliputi
pembuatan drift baru, yaitu DED (Dedicated Exhaust Drift), pembuatan ramp incline
dan decline, pembuatan heading dan pembuatan raise untuk produksi. Produksi di
Tambang Big Gossanakan dimulai tahun 2009 dengan produksi puncaknya pada
tahun 2011 dan akan ditutup pada tahun 2028.
Kegiatan peledakan yang dilakukan pada trial stope 38 level 3060 dan stope 4
level 3020 adalah untuk mengambil bijih tembaga. Pola pengeboran yang digunakan
adalah ring drilling selanjutnya dilakukan peledakan pada kedua level kemudian
hasil peledakan akan ditimbun di stope 4 level 3020. Kegiatan peledakan dapat
memberikan dampak berupa timbulnya overbreak pada stoping yang dapat
menimbulkan dilusi terhadap bijih tembaga. Untuk itu diperlukan adanya kajian
untuk mengetahui dampak dari peledakan tersebut.
Dari pengukuran getaran peledakan di stope 38 level 3060 nilai PPV
mencapai 187,76 mm/s, yang memberi efek getar akibat peledakan pada massa
batuan yang kondisinya tidak kompak sehingga terjadi runtuhan yang terekam pada
blastmont. Berdasarkan metode jarak terukur (Scaled Distances) nilai jarak aman
apabila ingin dibuat suatu bangunan di dekat titik peledakan adalah minimal 200
meter agar tidak terkena dampak getaran akibat peledakan. Dilusi yang terjadi
berdasarkan grafik ELOS pada sisi kiri stope (SWL) adalah 1, 4 m dan sisi kanan
stope (SWR) adalah 1,8 m. Berdasarkan hasil survey CMS nilai dilusi yang terjadi
pada sisi kiri stope sebesar 1,53 meter dan pada sisi kanan 1,75 meter, sehingga
didapat besar nilai dilusi aktual pada stope dengan ketinggian stope 40 meter dan
lebar stope yang direncanakan 15 meter serta panjang stope 5 meter adalah
186,2472 ton.
Kegiatan peledakan yang dilakukan di trial stope 38 level 3060 memberikan
dampak berupa timbulnya overbreak yang menyebabkan dilusi. Pengurangan jumlah
bahan peledak perlu dilakukan untuk meminimalisir terjadinya dilusi
KAJIAN DAMPAK TEKNIS PELEDAKAN BAWAH TANAH DI STOPE 38 LEVEL 3060 BIG GOSSAN MINE PT FREEPORT INDONESIA PROVINSI PAPUA
No full textKegiatan development yang dilakukan pada tambang Big Gossan meliputi
pembuatan drift baru, yaitu DED (Dedicated Exhaust Drift), pembuatan ramp incline
dan decline, pembuatan heading dan pembuatan raise untuk produksi. Produksi di
Tambang Big Gossanakan dimulai tahun 2009 dengan produksi puncaknya pada
tahun 2011 dan akan ditutup pada tahun 2028.
Kegiatan peledakan yang dilakukan pada trial stope 38 level 3060 dan stope 4
level 3020 adalah untuk mengambil bijih tembaga. Pola pengeboran yang digunakan
adalah ring drilling selanjutnya dilakukan peledakan pada kedua level kemudian
hasil peledakan akan ditimbun di stope 4 level 3020. Kegiatan peledakan dapat
memberikan dampak berupa timbulnya overbreak pada stoping yang dapat
menimbulkan dilusi terhadap bijih tembaga. Untuk itu diperlukan adanya kajian
untuk mengetahui dampak dari peledakan tersebut.
Dari pengukuran getaran peledakan di stope 38 level 3060 nilai PPV
mencapai 187,76 mm/s, yang memberi efek getar akibat peledakan pada massa
batuan yang kondisinya tidak kompak sehingga terjadi runtuhan yang terekam pada
blastmont. Berdasarkan metode jarak terukur (Scaled Distances) nilai jarak aman
apabila ingin dibuat suatu bangunan di dekat titik peledakan adalah minimal 200
meter agar tidak terkena dampak getaran akibat peledakan. Dilusi yang terjadi
berdasarkan grafik ELOS pada sisi kiri stope (SWL) adalah 1, 4 m dan sisi kanan
stope (SWR) adalah 1,8 m. Berdasarkan hasil survey CMS nilai dilusi yang terjadi
pada sisi kiri stope sebesar 1,53 meter dan pada sisi kanan 1,75 meter, sehingga
didapat besar nilai dilusi aktual pada stope dengan ketinggian stope 40 meter dan
lebar stope yang direncanakan 15 meter serta panjang stope 5 meter adalah
186,2472 ton.
Kegiatan peledakan yang dilakukan di trial stope 38 level 3060 memberikan
dampak berupa timbulnya overbreak yang menyebabkan dilusi. Pengurangan jumlah
bahan peledak perlu dilakukan untuk meminimalisir terjadinya dilusi
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