Dipyramidal Zircon Crystals From Alkaline Rocks of the Azov Region

2016 ◽  
Vol 38 (3) ◽  
pp. 9-23 ◽  
Author(s):  
V. Kvasnytsya ◽  
O. Vyshnevskyi ◽  
I. Kvasnytsya ◽  
I. Gurnenko
Keyword(s):  
2020 ◽  
Vol 42 (4) ◽  
pp. 3-22
Author(s):  
V.V. SHARYGIN ◽  
S.G. KRYVDIK ◽  
O.V. DUBYNA

Over recent years, new rare minerals have been discovered in the alkaline rocks of the Ukrainian Shield. Agpaitic varieties of alkaline magmatic and metasomatic rocks turned out to be especially abundant in rare minerals. Numerous findings are related to alkaline metasomatites which are considered to be fenites and apofenite albitites of the Dmytrivka quarry. It is well known primarily by the presence of various accessory (Nb, REE, and Zr) minerals, as well as silicate and oxide minerals that are rare for Ukraine. The most common albite microcline fenites of this quarry are characterized by rare-earth mineralization, whereas the concentration of REE decreases in apofenite albitites and Zr and Nb increase. New rare minerals were also found in the essentially albite rock with astrophyllite, alkaline pyroxene and amphibole of the Malatersa massif and agpaitic phonolites of the Oktyabrsky massif. In the rocks of the mentioned massifs and occurrences of alkaline rocks the most interesting are the findings of the perraultite — jinshajiangite series. They were found in three points of the Azov area and include 1) perraultite and jinshajiangite in the alkaline metasomatites of the Dmytrivka quarry; 2) only perraultite in agpaitic phonolites of the Oktyabrsky massif (Kam’yana gully); 3) jinshajiangite in a veined albite rock among the gabbro of the Malatersa massif. Baotite and minerals of the hejtmanite — bafertisite series were also found in the metasomatites of the Dmytrivka quarry. The latter belong to intermediate varieties in terms of MnO (10-17 wt.%) and FeO (10-17 wt.%) which distinguishes them from Fe-rich bafertisite from other regions. A silicate mineral with high content of Na, Zr, Mn and elevated Ti and Nb is rarely observed as small inclusions in the kupletskite grains from alkaline metasomatite of the Dmytrivka quarry. According to the chemical composition it was previously diagnosed as janhaugite. Tainiolite was found in some occurrences of alkaline metasomatites in the Azov region. In addition small aggregates of the REE-enriched epidote were found in fenites of the Kaplany village, which is probably the first finding in Ukraine. Two new Zr minerals have been found in the aegirine syenites of the Korsun-Novomyrhorod pluton: elpidite and mineral with a high content of Y2O3 (13-14 wt.%) (Y-hagatalite ?).


Author(s):  
I. Kvasnytsya ◽  
V. Kvasnytsya

The main basics in geometric crystallography of zircon, developed by many researchers in the 18th - 20th centuries, are briefly described. The data of goniometric study of zircon from crystalline rocks of the Ukrainian Shield (USh) are summarized. They cover zircon predominantly from granites and alkaline rocks of most the USh megablocks. The set of habit simple forms on zircon crystals is small: {111}, {110}, {100}, {221}, {331} and {311}. These forms define two contrasting habits of zircon crystals - prismatic and dipyramidal. Among the prismatic crystals several main morphological types of crystals are distinguished: {110} + {111} – zircon type, {100} + {111} – hyacinth type, {110} +100} + {111}, {110} +{100} + {111} + {311} and {110} + {100} + {311} – intermediate hyacinth-zircon types. Among the dipyramidal crystals two morphological types are contrasting — faceted by {111} dipyramid and {111} + {331} + {221} dipyramid combinations. The simple form {111} is developed on almost all zircon crystals from crystalline rocks of the USh, unless it is completely displaced on the heads of the crystals by the ditetragonal dipyramid {311}. For zircon crystals from syenites, mariupolites, albitites and some pegmatites the {111} is habit form. The simple form prism {110} is also developed on almost all zircon crystals from crystalline rocks of the USh, with the exception of many {111} dipyramidal crystals from syenites of the Zhovtnevy massif and hyacinth type of zircon crystals. It determines the most common morphological type of zircon crystals of prismatic habit – zircon type. The simple form prism {100} is less common on zircon crystals from crystalline rocks of the USh than the form {110}. It determines the hyacinth morphological type of zircon crystals of a prismatic habit. It is characteristic of zircon from granites of the Azov and Middle Dnipro regions. The simple form {311} is well developed on zircon crystals of hyacinth-zircon type from granites. It is almost absent on dipyramidal zircon crystals from alkaline rocks. The simple forms {221} and {331} are well developed only on dipyramidal crystals from syenites, mariupolites, albitites and some pegmatites of the Azov region. They are especially characteristic of zircon crystals of the Azov deposit. The simple form pinacoid {001} is rare and poorly developed; it was found only on zircon crystals of a prismatic habit from carbonatites of the Chernigiv massif and on dipyramidal crystals from syenites of the same massif. Another two dipyramids {101} and {211} can be attributed to reliable simple forms on zircon crystals from crystalline rocks of the USh. However, they are rare and found only on zircon crystals from acid rocks. Other goniometrically studied simple forms are poorly developed and incomplete, their reliability is questionable and therefore not accepted by us for consideration. The data presented on simple forms, habits and the main morphological types of zircon crystals from crystalline rocks of the USh almost completely confirm the main points on the morphological and structural bases of the crystallomorphology of zircon. First of all, this concerns two contrasting habit types of zircon crystals: dipyramidal crystals grow mainly in alkaline rocks and various morphological types of prismatic crystals grow in acidic rocks. In general, the set, the degree of importance and the distribution of simple forms on zircon crystals from crystalline rocks of the USh correspond to the morphological and structural series of crystals of this mineral. At the same time, the diversity of the morphological types of prismatic zircon crystals from granites still does not have a proper explanation. For the time being, it can be stated that each petrological type of granite can be characterized by a specific morphological type or types of prismatic zircon crystals. The dipyramidal zircon from most manifestations of alkaline rocks of the USh is younger than prismatic zircon from acidic rocks of the USh. Zircons from syenites of the Yastrubetsky and Zhovtnevy massifs and the Azov deposit have a Paleoproterozoic age of ∼1770 Ma. It characterizes the only stage of Paleoproterozoic alkaline magmatism, powerfully manifested in the USh and rich in rare-earth geochemical specialization. Dipyramidal zircons in these rocks are prevalent and even dominate (in mariupolites of the Zhovtnevy massif and syenites of the Azov deposit). Zircons from syenites and carbonatites of the Chernigiv massif, among which there are more rare dipyramidal crystals, are much more ancient - about 2000 Ma. Zircons from acidic rocks of the USh formed mainly in the period of 2.2–1.8 billion years. The dipyramidal zircon on the USh is a Precambrian formation, which reflects the Paleoproterozoic stage of the USh history, which is relatively narrow in time. Such zircon occurs in the Neogene and Quaternary terrigenous sediments of the southwestern part of the USh, which may indicate the presence in this area of still unknown Paleoproterozoic sources of alkaline magmatism. Dipyramidal zircon crystals may also belong to different albitized rocks and pegmatites of acidic and alkaline rocks.


2016 ◽  
Vol 38 (3) ◽  
pp. 24-38 ◽  
Author(s):  
S. Kryvdik ◽  
V. Sharygin ◽  
V. Gatsenko ◽  
E. Lunev
Keyword(s):  

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.


1968 ◽  
Vol 5 (6) ◽  
pp. 1401-1407 ◽  
Author(s):  
Ronald Doig ◽  
Jackson M. Barton Jr.

Potassium-argon ages have been determined for alkaline rocks, including carbonatites, from some fifteen localities in Quebec. Nine centers of intrusion, including two previously documented localities, yield ages in the range 400 to 600 million years. All but two of these are located on or very near the northern boundary fault of the St. Lawrence graben system. Included in this group are four carbonatites with remarkably similar ages of intrusion (565 m.y.). The existence of this widespread coeval igneous activity along a 1200-mile segment of the lowland area and its westward extension supports the hypothesis that the St. Lawrence graben is a continuous structure, and indicates that the system has been active for at least 600 million years.


Author(s):  
J. B. Allen ◽  
T. Deans

SummaryA detrital assemblage of magnesian ilmenite, pyrope, chrome-diopside, rutile, and zircon has been traced to outcropping ultrabasic alkaline rocks, hitherto unknown in the Melanesian region. Analyses and descriptions of these ‘kimberlite indicator minerals’ are given. The host rocks comprise alnöite, an alnöite breccia with calcite matrix, and a magnesian ankaratrite, which are described, with chemical analyses. Emphasis is laid on the abundance of ultrabasic inclusions and xenocrysts and the replacements and transformations they have undergone. Malaita Island promises to contribute significantly to the understanding of the relations between alnöite, melilite basalts, and kimberlites.


Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 354
Author(s):  
Anatoly M. Sazonov ◽  
Aleksei E. Romanovsky ◽  
Igor F. Gertner ◽  
Elena A. Zvyagina ◽  
Tatyana S. Krasnova ◽  
...  

The gold and platinum-group elements (PGE) mineralization of the Guli and Kresty intrusions was formed in the process of polyphase magmatism of the central type during the Permian and Triassic age. It is suggested that native osmium and iridium crystal nuclei were formed in the mantle at earlier high-temperature events of magma generation of the mantle substratum in the interval of 765–545 Ma and were brought by meimechite melts to the area of development of magmatic bodies. The pulsating magmatism of the later phases assisted in particle enlargement. Native gold was crystallized at a temperature of 415–200 °C at the hydrothermal-metasomatic stages of the meimechite, melilite, foidolite and carbonatite magmatism. The association of minerals of precious metals with oily, resinous and asphaltene bitumen testifies to the genetic relation of the mineralization to carbonaceous metasomatism. Identifying the carbonaceous gold and platinoid ore formation associated genetically with the parental formation of ultramafic, alkaline rocks and carbonatites is suggested.


2021 ◽  
Vol 37 (1) ◽  
pp. 231-252
Author(s):  
ZHANG Jian ◽  
◽  
LI HuaiKun ◽  
TIAN Hui ◽  
LIU Huan ◽  
...  

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