Val Vedello

For a long time we feel necessity for a quality change of Orobic Alps Geology that is not tied to hold ideas and models.

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Val Vedello Uranium Ore Deposit Geology


"Against the scientific mass illiteracy"



Premise


We live in a false alarms world, of environmental fundamentalist and misinformation in which politicized   “ experts”  they never miss. We live in a  world which the catastrophic forecasts are privileged and considered incontestable truths.The fundamentalist’s position is rarely tolerant of new information and is generally dismissive of evidence.   The “dissident” from these positions  are marginalized and hissed by the “ mediatic bass drum” and from the bureaucracies power. The “dissident” are shown as servants of industrial affairs and multinationals.

From years I read on the val Vedello uranium deposit  horrifying articles on national and local newspapers, nonsense unimaginable, deep misinformation. Great barbarism and free wickedness are found in abundance in many internet sites that is held of impeccable moral and technical correctness. These people drive the val Vedello uranium deposit in a radioactive atoll or, in the best of the hypotheses, in a site of mineralogical interest.

“Scientific”  publications, degree thesis, search doctorates, on val Vedello uranium deposit never miss of numerous superficialities and repetitive geologic and mining errors.


Val Vedello uranium ore deposit location and his short history

Val Vedello uranium ore deposits is the greatest uranium deposit in Italy.  It is located in northern Italy, northern part of the Bergamasque Alps (Orobian chain) and to south of Alpine Raetian Range.

Val Vedello uranium ore deposits is located immediately to NW of the watershed that separates the Valtellina valley (Sondrio Province) from the hydrographic basin of the Seriana valley (Bergamo province).The area  has rough reliefs up to 2700 m.  above sea level and include the Vedello and the Caronno  valleys . Ancient glacial cirques characterize morphologically the highest parts of the two basins. Uranium bearing rocks were detected in 1975 tanks an airborne gamma ray spectrometer survey and outcropping with subsequent radiometric prospecting and geologic surveying.

The mining search, located at an elevation among the 1800 and the 2100 m.  a.s.l,  began in 1977, on different adits, with the excavation of tunnels and exploratory evaluation drillings. The partially performed mining jobs, verified the presence of uranium bearing rocks for six hundred meters deep. The possible closing or the possible enrichments eventually present more at depth were not verified. Altogether eleven kilometers of tunnels and fifty thousand meters of core drilling were  performed. The presence of around six thousand tons of uranium (U3O8) of industrial grade was ascertained.

The search activities were suspended in 1983. The search suspension, happened therefore, some years before the Chernobyl disaster, in Ukraine (April 1986) and  the italian antinuclear referendum (November 1987), with which Italy gave up the “thin” nuclear that it already possessed, to supply him of electric energy produced by french and swiss commercial Nuclear Power Plants.

The val Vedello jobs and searches suspension, is clear, it was not due to uranium ore exhaustion in depth, but to other affairs.

 

Regional Geology short history

Following the Early Cretaceous Pangea breakup, the continental African plate approaching the European plate. The two continental plates are separated by a long and narrow Tethys ocean arm  subsequently recognized as Ligure-Piemontese ocean. So happens the subduction of the European plate under  African plate (Adria ) and the consumption of the crust of the Ligure - Piemontese ocean and the partial building of the rocks and the sediments (Early Cretaceous - Lower Eocene: eo-Alpine phase).

The following continental collision among the two continental plates with the overthrusting of the Adria plate over the European plate (Lower Eocene-Oligocene: meso-Alpine phase) the alpine chain  progressively built  is constituted in good part by the rocks of the ancient african border (Austroalpine) and subordinately from that european (Helvetides) with the interposition of the ancient Tethys rocks (Pennides).

 

 

In the Upper Oligocene to the Miocene (neo-Alpine phase) the alpine chain takes its final form with a marked uplift and erosion of the Alpine building. The great mountainous chain so produced is characterized by a double vergence of the thrust sheets; preponderant toward north, smaller toward south. The limit among the vergence ones is represented by a great, composite, regional feature called Insubric Line (Tonale segment for Lombardy portion).

The Southern Alps are found to south of the Insubric Line and show a general south- southeast vergence. The Southern Alps are constituted in good part by Paleozoic and Mesozoic unit. Is northern part is constituted by the ancient rocks of the pre-permian metamorphic basement  to which follow permian rocks characterized in their lower part by a strong volcanic and vulcanoclastic activity.

 

Val Vedello Geology

The geology of the Val Vedello and the neighboring areas, has been studied carefully, thanks to the presence of the most important italian uranium deposit.

The new geologic detailed field survey united to the underground geologic mapping carried out in the seventies, the radiometric dating effected on the uranium mineral ones (genesis of the Orobic Alps in the Early-Late Cretaceous transition) they have allowed to outline a geologic framework - deeply different from that looked out by the official geology and unfortunately still ignored today.

The val Vedello area is located in the northern Orobic Alps, south of the so called  “Tonale Line”, a great regional fault that marks the tectonic boundary between the Southern Alps domain and the more external structural complexes. In particular, in the Valtellina area, the “Tonale Line” divides the Southern alpine region (Orobic Alps) from the northern region (Retian Alps).

The  Southern Alps show thrust plane arranged whit classic imbricate fan geometries whit a general south-southeast vergence.

In the Vedello, Caronno and adjacent valleys, a  layer of intense mylonitization, fracturing and brecciation (
uranium bearing / barren) resulting from breaking and grinding of solid rocks materials, is located at the boundary between Morbegno Gneisses metamorphic basement rocks and the upper part of the Collio Formation cover. In this boundary occur cataclastic, mylonitic and ultramylonitic layers rocks, black or darked colored, with  lenticular boudined / layered, residual gneisses and stretched quartz pebble resisters lineations.

In val Vedello the mylonite band strikes generally between North-East and North and dips 30° to 70°to the East. This Early Permian tectonic limit is due to an extensional fault on a preexisting oldest fault  structure. PreAlpine basic dykes- uranium bearing / barren- are sometimes present.

Val Vedello fanglomerates upper Collio Formation strata displaying monoclinally dipping toward north or northwest.                        

Pre-Alpine structures and uranium bearing rocks are cut by frequent Alpine East-West striking faults, North dipping reverse faults that divide into blocks the entire complex. Finally some extensional faults WNW dipping and NW-SE strike, steeply dipping  normal faults, representing the most recent tectonic events. Tertiary porphyritic dikes intrude some of them.

 

Val Vedello uranium ore deposit  features

Northern Orobic Alps is an uranium province.The uranium deposits in the Alps are related to the Hercynian orogeny.

The Val Vedello Late Hercynian hydrothermal uranium occurrences vein-type deposit are located on the right slope of the Vedello valley and related to major extensive fault and mylonitic zones (rejuvenation of Variscan mylonitic zones) between the metamorphic Variscan basement and Permian cover.

The uranium mineralization is always conformable whit the main tectonic trend, that is parallel to the bearing of the mylonitic bands. Both along the strike and along the dips, the uranium mineralization may disappear and reappear, and grade  and thickness may vary. Uranium bearing rocks dipping east, southeast showing primary uranium minerals as uraninite(UO2), polyphasic pitchblende(U3O8) and brannerite(UTi2O6),  in varying ways, in  association to various iron-copper oxide/sulphides and carbonates. Pitchblende is the most typical uranium mineral of the val Vedello. High grade ore up to 10% may be locally present. Oxidized uranium minerals are occasionally present, both in surface alteration zone that in underground. The most known are: Torbernite, Meta-Autunite and Gummite.

It is important to underline as the scarce presence of uranium secondary minerals show the scarce water interaction with the uraniferous minerals.

The geochronological age of the main  uranium mineralisation (around 250 Myr. ) show a delay recurrent in the literature also from similar metallogenetic events. Leaching solutions fed by the  Permian ignimbrites and circulating along the main Permian and Triassic fault systems discharged uranium and other minerals into structural-chemical traps located at shallow depths and at the intersection whit convenient lithological unit. These mineralisation  also are characterized by carbonatisation in the country rocks.

 

Successively the uranium mineralisation have been dismembered by Alpine deformation phases  and two types of minor uranium ore are evident in Alpine reverse faults, East-West directed  and North dipping:

--  Mobilized Uranium ore locally present into brittle E-W Alpine trending.

--  Permian cataclastic-mylonitic layers uranium bearing rocks catched  into the East-West  fault plans.

Alpine orogenetic stresses has been remobilized  and chronologically rejuvenated (100 my old) these minor Uranium ore deposits.