Projects & Operations - Deposit Geology   |  Shinas & Hatta Project


Deposit Geology - Hatta Extended  |  Hatta South  |  Shinas

Hatta
Stage 4 infill and extensional drilling in 2003 indicated the movement on post mineralization structures that disrupt the shallow southeast dipping massive sulphide mound sheet and underlying axially located stockworks. The central mound of the deposit features very high primary copper grades which diminish on the flanks and tend to include stronger zinc and locally peripheral gold mineralisation.
 

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Click to enlarge

The deposit rapidly wedges out laterally into haematitic or jasperous exhalative sediments and remains open to the north beneath Wadi Hatta where strong stockwork development and IP anomalism indicates potential for discovery of new sulphide mineralisation in down-faulted blocks in addition to the current resources of 0.96Mt at 3.41% Cu.

Recent petrological data in support of defining metallurgical ore types shows the feeder zone at Hatta is a mineralised breccia with a multi-stage paragenesis which commenced with intensely chloritized, small, angular basalt clasts and progressed to a hydrothermal matrix involving early pyrite, subsequent and dominant specular hematite then late calcite, and terminated with the development of gypsum which over printed all other mineral phases.

The overlying seafloor massive sulphide deposit consisted of early exhalative pyrite–silica cemented mounds which were locally banded or bedded with minor chlorite, chalcopyrite and sphalerite, and interbedded with specular or earthy heamatite in peripheral zones where alternating reducing and oxidizing conditions occurred. Ongoing hydrothermal activity produced common brecciation with dominant pyritic clasts in a silica-sulphidic cement that included chalcopyrite and minor sphalerite accompanied by calcite, siderite and chlorite. The final event involved prominent, irregular veining by gypsum.

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Hatta Extended
This small high-grade deposit comprises two SE dipping sheets of massive sulphide that remain open up-dip to the west. Proposed drilling in 2005 will determine whether this deposit is large enough to warrant inclusion in the mining reserves and also test strike and dip extensions that exhibit geophysical anomalism.

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Hatta South
The deposit comprises a small shallow massive sulphide mound up to 25metres thick in HS-05 with a restricted axial stringer zone that extends up-dip to a gossan zone to the west. To the north mineralisation appears to be cutoff by ESE trending faults but south of a central dolerite dyke the deposit forms a thin sheet-like lens of pyritic breccia cemented by chalcopyrite extending 150m x 100m and dipping SE at 15deg.

Petrology to identify the mineralization paragenesis and distinguish massive sulphide ore types showed early breccias similar to Hatta with indistinct massive sulphide clasts, characterized by pyrite and chalcopyrite in a hydrothermal cementing matrix featuring pyrite and quartz with some calcite and chlorite. Late quartz veining carries (iron-poor) sphalerite with small amount of chalcopyrite is locked as tiny exsolution inclusions within the sphalerite, and residual vugs are filled with late calcite and gypsum or illitic clay. Previous drilling at 40 x 25m spacing enabled definition of a polygonal estimated resource of 430,000 tonnes at 2.7% Cu, however, in fill drilling is necessary to properly define ore blocks, provide material for metallurgy and design a mine plan. The lower grade ore near surface proves scope for early mining and blending of ore with the supergene high-grade ore at Hatta for plant commissioning.

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Shinas
Although the overall deposit parameters are outlined, Shinas remains the least well known deposit because of the obscuring gravel and the presence of key faults that make it difficult to measure the position and limits of mineralization blocks. The western side of the deposit including the auriferous gossan hill breccia remains poorly defined and it is also possible isolated locks of sulphide mineralisation will be found in marginal zones and at depth.
 

Shinas section 2740850N, Showing Drilling, CuAu Grade Histograms and Geological Interpretation Click to enlarge

Shinas Deposit Showing Water Monitoring Wells, Ore Blocks,Propose Open Open pit and Channel 13 TEM Click to enlarge

In order to better define the metallurgical ore types present, further petrological work in 2004 showed that silicification overprints pre-existing mound massive sulphide and exhalative silica, with various siliceous and sulphide rich overprinting phases including jasper (silica and hematite) indicating a change to more oxidized fluid conditions late in the paragenesis In general, after initial brecciation hydrothermal action progressed to crystallization of dominant pyrite as crusts on the first generation siliceous clasts and as second generation clasts of massive pyrite.

The final hydrothermal cementation of the two stage breccia involved crystallization of additional fine quartz, accompanied by plentiful disseminated pyrite and small amounts of interstitial sphalerite and chalcopyrite. More recent near surface supergene alteration has generated chalcocite by partial replacement of pyrite, sphalerite and chalcopyrite, mainly within the hydrothermal matrix.

The difference between deposit morphology and ore types at Shinas and Hatta is explained by the precursor footwall brecciation at Shinas together with relatively silica-rich fluids, resulting in an early dominant siliceous sulphide matrix and a late assemblage dominated by jasper at Shinas compared to the hematite at Hatta.

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