Ylijoki - Gold Database

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Name	Ylijoki	DATA UPDATED	12.1.2007
Alternative names	Kivenneva
Deposit summary	YLIJOKI, in Southern Ostrobothnia, is a Palaeoproterozoic orogenic gold occurrence with no resource estimate available. It is formed by a set of quartz veins in mica gneiss. The deposit is close to a major NW-trending shear zone.
LOCATION
Geological domain	Svecofennian	Belt	Southern Ostrobothnia
Site photo		Regional map
Map sheet	222112
Northing (kkj)	6947730	Easting (kkj)	2451950
Latitude	62.63083N	Longitude	23.06004E
Municipality	Nurmo
Nearest town, roads	20 km SE From Seinäjoki. 4 km from a sealed road, a gravel road to the area.
MINING
Exploration licence no	4673/1	Mining concession no
Present holder	OPEN FOR ACQUISITION
Previous holders	Geological Survey of Finland (GTK) (1987-1993)
Mine photo 1		Mine photo 2
Mine photo 3		Mine photo 4
Status of development	Prospect
When mined
Resources
Deposit size (Mt)		Reference (size)
Total in-situ gold (kg)		Reference (in-situ Au)
Total gold production (kg)		Reference (gold prod)
Production of other metals
Extent of mineralisation
Lodes
Best sections	7 m @ 1 ppm Au, 1 m @ 6.7 ppm Au [2].
EXPLORATION
Discovery year	1987
Discovery	By GTK: gold analysed on arsenopyrite-bearing quartz veins in outcrop [1,2].
Exploration history	GTK (1981-93) [1,2]: Regional (1981) and localised (1986-) till geochemistry, till stratigraphy, bedrock mapping. Localised studies on 1988-1993 [2]: electric and magnetic ground survey, trenching, diamond drilling.
Section figure 1		Plan figure 1
Section figure 2		Plan figure 2
Section figure 3		Plan figure 3
Trench fig 1		Trench fig 4
Trench fig 2		Trench fig 5
Trench fig 3		Trench fig 6
Explor site photo 1		Explor site photo 2
Geophysical response	Good response by combining the IP and the magnetic method [2].
Drilling	GTK (1988-1990): 11 diamond-drill holes, total 420 m, across the narrow geophysical anomaly [2].
Elements analysed
Primary dispersion	There is no obvious correlation between Au and As in local scale [2].
Secondary dispersion	Extensive Au anomalies in the region in till, but practically no local indications of elevated Au [1].
Primary anomaly fig 1		Secondary anomaly fig 1
Primary anomaly fig 2		Secondary anomaly fig 2
Primary anomaly fig 3		Secondary anomaly fig 3
Primary anomaly fig 4		Secondary anomaly fig 4
Primary anomaly fig 5		Secondary anomaly fig 5
Economic evaluations
Exploration geologist in charge	GTK: Niilo Kärkkäinen.
ORE
Siting of gold
Fineness
Major opaques	Arsenopyrite [2].
Minor opaques	Pyrrhotite, gold [2].
Gangue	Quartz [2].
Ore miner. photo 1		Ore miner. photo 5
Ore miner. photo 2		Ore miner. photo 6
Ore miner. photo 3		Ore outcrop photo 1
Ore miner. photo 4		Ore outcrop photo 2
Ore composition
Enriched elements
Ore fluid
Stable isotopes
Pb isotope data
GEOLOGY
Geological setting	The Palaeoproterozoic mica gneiss has been interpreted as a sequence of arkositic greywackes and altered, intermediate, metavolcanic rocks [2].
Major host rocks	Mica gneiss [2].
Minor host rocks
Intrusives	A granodiorite 500 m to the WSW of the mineralisation and a 200 m wide pegmatite dike at the contact between the mica gneiss and the granodiorite intrusion [2].
Regional geol map 1		Outcrop photo
Regional geol map 2		Outcrop photo 2
Local geology map 1		Outcrop photo 3
Local geology map 2
METAMORPHISM
Metamorphic history
Metamorphic grade
Metamorphic mineral assemblage
Metamorph photo 1		Metamorph photo 2
STRUCTURE
Structural style
Closest major shear	A NW-trending shear zone extending from Seinäjoki to Peräseinäjoki, >30 km long, 1 km(?) wide [2].
Controlling structure
Deformation history
Ore fabric
Veins	A set of auriferous, 0.1-60 m wide, quartz veins [2].
Structure photo 1		Vein photo 1
Structure photo 2		Vein photo 2
Structure photo 3		Vein photo 3
ALTERATION
General alteration
Proximal alteration
Intermediate alteration
Distal alteration
Zonation figure		Prox alteration photo 1
Alteration photo 1		Prox alteration photo 2
Alteration photo 2		Intermed alteration photo
Alteration photo 3		Distal alteration photo 1
Post-mineralisation modifications
TIMING
GENETIC MODEL	Orogenic"mesothermal" deposit.
GENETIC TYPE	Orogenic	References
Alternative genetic type 1		References
Alternative genetic type 2		References
References 1. Kärkkäinen, N. 1992. Kultamalminetsintää Nurmon Ylijoen alueella ja Ämmälänkylässä v. 1988-1990. Geol. Surv. Finland, Report M19/2221,2222/-92/4/10 . 15 p. (in Finnish, 9.8 MB)
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