Leucocratic Granites Research Articles

Aspects of tin metallogenesis in the Tasman Geosyncline, eastern Australia, as reflected by cluster and factor analyses

Geochemical classification of 284 granitic rocks from the Tasman Geosyncline, eastern Australia, demonstrates the association of tin deposits with leucocratic granites of high tin content. The mean Sn content (26 ppm) in such rocks is about seven times higher than in “barren” granites. Factor analysis of geochemical data indicates differences in the geochemical evolution of various rock types and the relative importance of magmatic differentiation and postmagmatic alteration in determining the composition of rocks in various areas of the geosyncline.

Some geochemical aspects of tin mineralization in the Tasman Geosyncline

Differentiation analysis using Kohler-Raaz indices has been applied to 284 granitic rocks from various parts of the Tasman Geosyncline in Queensland, New South Wales, Victoria and Tasmania. It was found that the majority (about 80%) of rocks known to be associated with tin mineralization (mostly leucocratic granites and adamellites) have a well defined range of Kohler-Raaz indices (qz=60–70%, F=20–25%, fm=5–15%) in agreement with findings in other parts of the world. Rocks associated with cassiterite deposits usually have a higher tin content than those not carrying cassiterite — but this information has to be used with caution because the form of tin in the rock (i. e. as an economic mineral e. g. cassiterite or in a host mineral, e. g. in biotite) is determined by several factors. All these factors (geochemical, physicochemical and geological) must be considered in an integrated approach to exploration for new tin deposits.

The Gander Lake and Davidsville Groups of Northeastern Newfoundland: New Data and Geotectonic Implications: Discussion

A large number of papers on Newfoundland geology have appeared lately, many of them stimulated by the publication of the plate tectonics hypothesis some four years ago. Kennedy and McGonigal (197'2) have recently added another, this one an interpretive paper on the tectonic events in northeastern Newfoundland. It should surprise no one even slightly familiar with the region that interpretational conflicts might arise. for rocks are very poorly exposed in northeastern Newfoundland (<5 5% outcrop) and much extrapolation, speculation, and imagination are generally required to arrive at any interpretations. Crucial to many of the authors' conclusions is the age of the leucocratic granite. This they regard as intrusive into their metasedimentary terrane (i.e. into the lower unit of the Gander Lake Group1 ), and interpret it as pre-Middle Ordovician in age. Exposures of this peculiar garnetiferous, pcgmatitic, sodic, white muscovite granite occur with a northeasterly trend and at irregular intervals along the entire eastern side of the Gander River ultrabasic belt. With few exceptions they lie west of the migmatites and porphyritic reddish biotite granites in northeastern Newfoundland. Two such bodies of lcucocratic granite south of Gander Lake have 'Throughout this discussion 1 have used the term Gander Lake Group as it was originally defined (Jenness 1958, 1963), for reasons that will be apparent later in the discussion.

Geological indications in prospecting for residual or redeposited kaolins in Mesozoic weathered crust, Ural

The southern part of the Transuralian peneplain is shown to be a particularly favorable ground in prospecting for economic deposits of kaolin, ceramic grade, and for kaoliniferous sands, on paleoclimatic-paleogeographical premises and on the basis of stratigraphic, petrographic, and other evidence. Facies-lithological, geomorphological, and structural-tectonic criteria further define the areas in which accumulations of kaolins (derivatives of alaskite and leucocratic granites) may be discovered.

Beneficiation technology for the vodora zdel' noe leucocratic granite

Beneficiation technology for the vodora zdel' noe leucocratic granite

Basic and intermediate igneous activity and its relationships to the evolution of the Julianehåb granite, South Greenland

In the area investigated, situated in the eastern part of the Julianehåb granite region, six granite varieties constitute large areas between which mainly ENE-trending belts of gneiss and metamorphic supracrustals are preserved. Much of the granite probably represents anatectic pre-Ketilidian basement. Three varieties belong to the 1st episode of Ketilidian plutonism. Three younger mainly allochthonous varieties (2nd episode) were generated in connection with basic and intermediate igneous activity. One of the oldest (pre-1st episode) basic intrusive bodies was probably intruded into a granitic part of the pre-Ketilidian basement. Others occur in Ketilidian metavolcanics. Six types of calc-alkali basic and intermediate intrusives postdate the 1st episode. The metadolerites are mainly concentrated in the Julianehåb granite region and are interpreted as intraorogenic. Some of the hypersthene gabbros might be contemporaneous with the metadolerites. The first phase of the 2nd episode of Ketilidian plutonism is characterised by deformation, and emplacement of allochthonous granite bodies which was controlled by older fold structures. A slow process of consolidation in the cores of the bodies eventually permitted the intrusion of the synkinematic dykes mainly concentrated there. Before these dykes were intruded the crustal conditions in the margins of the bodies and outside permitted the intrusion of the pyroxene-bearing diorites and possibly of some hypersthene gabbros during the earlier stages of the formation of the Big-feldspar granite of the second phase. The second phase is furthermore marked by migmatisation of basic and intermediate intrusives in a broad belt surrounding the southern part of the Big-feldspar granite. The latest phase of granite development, mainly confined to the eastern part of the Julianehåb granite region, is marked by emplacement of leucocratic granites and passive remobilisation of older granites followed by intrusion of the net-veined diorites and leucocratic veining. Finally, swarms of slightly metamorphosed tholeiitic dykes mark the transition from plutonic to cratogenic conditions. Evidence is presented suggesting that the eastern part of the Julianehåb granite region constitutes the site of the latest thermal activity in the Ketilidian mobile belt. In addition, differences in crustal conditions between this part and the surrounding regions during earlier stages of the plutonic evolution are considered.

Characteristics of molybdenum stockwork deposit in eastern Transbaykalia

The type of this deposit is unusual for the region and the stock ore body lies outside the region's gold-molybdenum belt, in the area abounding in volcanic and subvolcanic rocks. The concentrically-zoned structured body is associated paragenetically with post-Upper Jurassic leucocratic granites; it appears to have been formed at shallow depths and at intermediate temperatures, as a member of the quartz-molybdenite-sericite formation, from neutral and weakly alkaline solutions. -- V.P. Sokoloff.

Experience with enriching leucocratic granites

Experience with enriching leucocratic granites

Petrographic and mineralogical features of amblygonite- and spodumene-carrying granites

Granites carrying amblygonite and spodumene are characterized by 1) little if any, biotite; 2) strong alteration of rock-forming minerals; 3) development of potash feldspar over plagioclase in amblygonite granites; 4) development of plagioclase over potash feldspar + an epidote-garnet accessory mineral association in spodumene granite; 5) concentration of rubidium in amblygonite granites rich in potash feldspar. Amplygonite granite is most typical of greisenized granites and spodumene, of albitized granites. Chemically spodumene granites are of sodium type (Na/K>1), the amblygonite varieties are of potassium type (Na/K<1), and accessory epidote and tourmaline of spodumene and amblygonite granites are richer in lithium than those in common granites. Fluorine in the greisenizing solutions promoted transfer and deposition of lithium as amblygonite. Altered leucocratic granites are most likely to contain lithium minerals. The criterion for lithium presence is its higher content in pneumatolytic and hydrotherm...

Stratigraphy and Geological Structure of the Usuki Area, Oita Prefecture, Kyushu (1)

1) The Usuki area in eastern Kyushu belongs to the so-called Chichibu Terrain of the Outer Zone of Southwest Japan., This mountainous area comprises rocks of the Chichibu supergroup, largely of the Permian period and less so of the late Mesozoic., They are arranged in a number of parallel or nearly parallel belts of NEE-SWW trend and separated by tectonic lines., 2) From paleontological and other evidences, the respective ages of the formations are as follows., (Fossils listed in Japanese text) Mesozoic formations: Shinkai formation., ., ., ., ., ., ., ., ., ., ., ., ? ., ., ., ., ., ., ., ., ., ., ., ., Upper Jurassic Yamabu formation., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Kochian (Kl., Lowest Cretaceous) Haidateyama formation., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Miyakoan (K3., Upper part of Lower Cretaceous) Tano formation ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Gyliakian (K4., Lower part of Upper Cretaceous) Palaeozoic formations: Those in the Chinnanzan tectonic belt., ., ., ., ., ., ., ., ., ., ., ., Partly Lower Permian Those in the Tsukumi tectonic belt., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Lower-Middle Permian Those in the Meiji tectonic belt., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Lower-Middle Permian Katauchi formation., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., ., Visean (Lower Carboniferous) ? Those in the Usuki, Nakano and Kashimine tectonic belts., ., ., ., ., ., ., ., ., undetermined 3) Each of the tectonic lines which separates the formations into the tectonic belts is not a simple fault but a narrow zone containing several faults accompanied with a sheared zone., Peculiar igneous and metamorphic rocks squeezed out along these tectonic lines are found frequently., They are leucocratic granite, schistose diorite-gabbro, quartz-porphyry, porphy-rites, hornblende-bearing biotite granite, gneiss and serpentinite., The structural features are similar to those in the Yatsushiro-Kuma area., (See T., MATSUMOTO and K., KANMERA, 1949)., 4) The Paleozoic rocks are generally intensely folded and locally metamorphosed, while the Mesozoic rocks are moderately folded., 5) It is noteworthy that an important tectonic epoch towards the mid-Cretaceous is indicated by the unconformity between the Haidateyama (K3) and the Yamabu (K7) and the Paleozoic formations., The post-Cretaceous (or at least post-Gyliakian) crustal movements also play an important role in the development of the geological structure of the Usuki Area.,