Jerseyi

Regional Level Types
Jersey	Crown Dependency

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Jersey, officially the Bailiwick of Jersey (French: Bailliage de Jersey; Jèrriais: Bailliage dé Jèrri), is a British Crown dependency near the coast of Normandy, France. It is the second-closest of the Channel Islands to France, after Alderney.

Geology:
"Although the island has produced very little ore the quarrying industry has always been important. Metalliferous mining ventures have included iron ore at La Corbière, molybdenite at L' Etacq, copper at La Moye and, most seriously, lead-silver at Le Pulec.
The geology of Jersey is shown in Figure 4. The Cambro-Ordovician Rozel Conglomerate unconformably overlies the Jersey Volcanic Group, a series of andesites overlain by rhyolites. Beneath the Jersey Volcanic Group is the Brioverian Jersey Shale Formation. These rocks have been intruded by Cadomian igneous rocks, namely the Northwest Complex. The rocks are calc-alkaline and range from granite to diorite. Mineralization has been reported in all of the main divisions except for the Rozel Conglomerate (Bishop and Bisson 1989).
The Jersey Shale Formation, comprising mudstones and conglomerates but mainly siltstones and sandstones, has suffered chlorite grade metamorphism. Locally the formation is host to minor mineralization. At Meadow Banks, in the German Hospital Tunnels, calcareous mudstones are cut by galena, sphalerite, pyrite, marcasite, chalcopyrite and calcite veinlets or by quartz veins carrying chalcopyrite, pyrite, sphalerite, galena and traces of bournonite. Nearby lenses of disseminated, banded pyrite are present in a highly altered acidic dyke that cuts the metasediments; in this assemblage pyrite, chalcopyrite, galena and sphalerite are accompanied by trace amounts of molybdenite and pyrrhotite (Ixer 1980, 1990). Other lenses in the dyke are composed of quartz and chalcopyrite (Mourant pers comm 1988).

More substantial mineralization is hosted by the Jersey Shale Formation at Le Pulec, a small bay on the northwest coast, close to the junction of the shales and the Northwest Granite. In 1871 three sphalerite-galena-carbonate veins were discovered on the foreshore. The veins cut the shales and were of variable length; the longest (Lode No. 1) had a trend of 300o and was approximately 180m long, whilst the other two were less than 100m long with trends of 300o (Lode No. 2) and 275o (Lode No. 3). The width of all three was between 0.5 - 2.0m. Good silver values for the galena were reported by Williams (1871) and independently by Ogier (1871). Intermittent attempts were made to mine the veins (between high tides) from 1872 to 1876 when mining was abandoned (Mourant & Warren 1934, Howell 1977).

Two of the lodes are exposed (Nos. 1 & 3) and their mineralogy and petrography have been described by Ixer & Stanley (1980) and Stanley & Ixer (1982). At Le Pulec the Brioverian shales close to the granite contact have been bleached and silicified and carry sulphide-arsenide mineralization, namely early pyrrhotite (now altered to tabular pyrite and marcasite), pyrite and finally arsenopyrite with minor chalcopyrite, galena, sphalerite and molybdenite. Cross-cutting this mineralization are the three veins, at least one of which is associated with a highly altered basic dyke (Howell 1977). Within the limited sampling allowed, lodes 1 and 3 are the same and are composed of polyphase mineralization. The sequence is:-

1) ferroan dolomite and iron-poor sphalerite

2) a number of generations of quartz-minor chlorite plus galena, sphalerite, chalcopyrite, cubanite, tetrahedrite, bournonite, native antimony and traces of silver sulphosalts.

3) ferroan calcite, stibnite and other antimony sulphosalts.

Analyses of the tetrahedrite show it to have been the main silver carrier with 6 - 20 wt % Ag and rarely up to 40 wt %. Potassium-Argon dating of the altered basalt next to lode No. 1 has given 424±4 Ma, a Silurian age (Ineson per comm. 1982).

Very minor amounts of mineralization are present in the overlying Jersey Volcanic Group. Sometime in the middle of the nineteenth century at West Mount on the outskirts of St Helier, an audit was driven into green-stained tuffs and agglomerates, close to a dolerite intrusion (Mourant & Warren 1934). Similar mineralization has been noted from Bouley Bay where the green-stained Middle Bouley Ignimbrite has very fine quartz net-veining with chalcopyrite, bornite-chalcopyrite intergrowths ("idaite") plus minor pyrite and enargite. Secondary alteration to blaubleibender-covelline, covelline, malachite, limonite and cuprite is responsible for the colouration of the outcrops.

The Southwest Granite (dated 553 ± 12Ma, Adams 1976, Bishop & Bisson 1989) carries minor quartz-sulphide joint infills and was host to nineteenth century trial diggings at La Corbière for iron ore, whilst at La Moye a copper vein was discovered in 1843 but not exploited (Mourant & Warren 1934).

At La Corbière quartz-chlorite veins carry "massive" magnetite-haematite-rutile followed by later haematite, pyrrhotite, pyrite, chalcopyrite, galena and sphalerite. At L'Ouaisné Bay thin joint infills are composed of quartz-calcite-fluorite-chlorite with haematite, sphalerite, galena and minor magnetite, rutile, pyrite and a little chalcopyrite.

At La Moye the granite/aplogranite is net-veined by bornite, bornite-chalcopyrite intergrowths ("idaite") and tetrahedrite-bearing quartz veinlets. Extensive alteration is responsible for the malachite and azurite staining (Ixer 1988).

The Northwest Granite of the Northwest Igneous Complex is the largest and youngest of the three granites and is dated at 480Ma. In joints at L'Etacq Quarry the granite carries quartz-calcite veins with molybdenite (which may have been collected and sold to collectors), pyrite, chalcopyrite, sphalerite, marcasite, arsenopyrite, galena, pyrrhotite, bournonite, tetrahedrite and stannite (Ixer 1980) plus silver-rich cosalite and boulangerite (Mourant 1985). Molybdenite was collected from the china-stone quarries at Handois. Elsewhere in the granite, quartz veins have pyrite, marcasite, chalcopyrite, sphalerite, molybdenite, bournonite and native antimony as at Gigoulande Quarry, or carbonate veins carrying arsenopyrite, pyrite, sphalerite, galena plus minor chalcopyrite, marcasite, haematite, pyrrhotite, tetrahedrite, magnetite and bornite as at Douet de la Mer.

The Southwest Igneous Complex has no recorded mineralization, but carbonate veinlets cutting the Fort Regent Granophyre carry haematite, chalcopyrite and marcasite, whereas in Queens Valley quartz-carbonate veins enclose chalcopyrite-bornite-tetrahedrite intergrowths with minor quantities of galena, sphalerite and pyrite.

An island-wide synthesis of these mineral occurrences has been given by Ixer (1980) who suggested a number of ore associations, namely:

1) porphyry-style copper mineralization in the Jersey Volcanic Group (Bouley Bay)

2) quartz-molybdenite-base metal sulphide pegmatitic veins followed by quartz-carbonate-base metal sulphide hydrothermal veins, both cutting granites

3) unclassified carbonate-sulphide veinlets in the Jersey Shale Formation

4) Le Pulec

With the advantage of additional material, both from Jersey and the other islands, the mineralization can be simplified.

Polymetallic mineralization associated with granites has the following sequence: magnetite/haematite, pyrrhotite, pyrite, arsenopyrite, base metal sulphides and finally antimony-bearing phases. Tin and tungsten minerals are noticeably scarse on the island, only trace amounts of stannite have been positively identified. The youngest Northwest Granite appears to be more evolved than the other granites, with greater amounts of molybdenum, antimony, silver, tin and bismuth in its associated mineralization.

All of the mineralization in the Jersey Shale formation (Le Pulec and the German Underground Tunnels) is similar. Briden et al (19892) have suggested, on geophysical grounds, that the Northwest and Southwest granites are joined at depth and that the Jersey Shale Formation is only 0.25km thick. If this is so then the base metal, minor antimony, with or without silver mineralization, could also be a manifestation of the granites.

However, the presence of post-Brioverian dykes at both sites of mineralization is worth noting (dykes are also recorded close to the mineralization at West Mount and at Douet de la Mer) as an alternative/additional factor in the ore formation process. The dykes are too small to be the direct cause of mineralization and may just have used the same fractures as the mineralising fluids. The chemistry of the dykes, which is very different from that of the metasediments, may have promoted mineralization. The regional heat source responsible for the dykes may also be responsible for localized mineralising systems."
(http://www.rosiehardman.co.uk/taxev.htm)

Jersey was part of the Duchy of Normandy, whose dukes went on to become kings of England from 1066. After Normandy was lost by the kings of England in the 13th century, and the ducal title surrendered to France, Jersey and the other Channel Islands remained attached to the English crown.

The bailiwick consists of the island of Jersey, the largest of the Channel Islands, along with surrounding uninhabited islands and rocks collectively named Les Dirouilles, Les Écréhous, Les Minquiers, Les Pierres de Lecq, and other reefs. Although the bailiwicks of Jersey and Guernsey are often referred to collectively as the Channel Islands, the "Channel Islands" are not a constitutional or political unit. Jersey has a separate relationship to the Crown from the other Crown dependencies of Guernsey and the Isle of Man, although all are held by the monarch of the United Kingdom.

Jersey is a self-governing parliamentary democracy under a constitutional monarchy, with its own financial, legal and judicial systems, and the power of self-determination. The Lieutenant Governor on the island is the personal representative of the Queen.

Jersey is not part of the United Kingdom and has an international identity separate from that of the UK, but the UK is constitutionally responsible for the defence of Jersey. The definition of United Kingdom in the British Nationality Act 1981 is interpreted as including the UK and the Islands together. The European Commission confirmed in a written reply to the European Parliament in 2003 that Jersey was within the Union as a European Territory for whose external relationships the UK is responsible. Jersey was not fully part of the European Union but had a special relationship with it, notably being treated as within the European Community for the purposes of free trade in goods.

British cultural influence on the island is evident in its use of English as the main language and the British pound as its primary currency, even if some people still speak or understand Jèrriais, the local form of the Norman language, and place names with French or Norman origins abound. Additional British cultural commonalities include driving on the left, access to the BBC and ITV regions, a school curriculum following that of England, and the popularity of British sports, including cricket.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.

Mineral List

Mineral list contains entries from the region specified including sub-localities

55 valid minerals. 3 erroneous literature entries.

Rock Types Recorded

Rock list contains entries from the region specified including sub-localities