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"magmatism"
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What are igneous rocks?
Igneous rock has a dramatic beginning--it requires red-hot volcanic activity. This fact-filled book explains how granite, lava, basalt, silica, quartz and feldspar are formed after hot, molten rock cools.
Book
Ar/sup.39Ar age of gold mineralization of the Malomyr deposit
Reliable age estimation was obtained originally in this study for gold mineralization of the Malomyr deposit (the eastern part of the Mongolian-Okhotsk foldbelt), which is one of the most well-known deposits in the Russian Far East. The data obtained show that the age of hydrothermal process that resulted in the formation of the Malomyr deposit may be estimated as ~133-132 Ma. Data on magmatism of the same age within the considered region are absent. In the opinion of the authors, mobilization, redistribution of the ore material, and the formation of the Malomyr deposit were mostly controlled by dislocation processes accompanied by hydrothermal activity, which is supported by the results of structural studies. DOI: 10.1134/S1028334X16010153
Journal Article
Isotopic U-Pb Age of Zircon : First Evidences for Post-Collisional Ore Formation in the Kurama Segment of the Middle Tien Shan
The paper presents isotopic U-Pb zircon data (LA-ICP-MS method) for the main types of high-potassic intrusive rocks of the Chorukh-Dairon W-Mo(-Cu-Au) skarn deposit situated in the Kurama segment of the Middle Tien Shan near the largest porphyry Cu-Mo-Au deposits of the Almalyk mineralized cluster. Together with the other Au, W, Mo and Cu deposits, all these deposits are parts of the extended Late Paleozoic metallogenic belt of Tien Shan. The concordant isotopic U-Pb zircon data obtained for the rocks of successive intrusion phases in the Chorukh-Dairon pluton span from about 298 Ma to 290 Ma. This interval included crystallization of monzodiorite (295.1 ± 3.3 Ma), quartz syenite (294.7 ± 2.3 Ma), quartz monzonite (294.1 ± 2.1 Ma), and monzogranite (293.0 ± 3.0 Ma). These dates correspond to the pluton emplacement at the Late Carboniferous-Early Permian boundary and highlight its younger age compared to the productive high-potassic intrusions of the porphyry Cu-Mo-Au deposits in the Almalyk mineralized cluster, the latter assigned to the Late Carboniferous (about 337-313 Ma and partially to 308-297 Ma). By contrast to the latter, which were intruded in the subduction-related environment, the emplacement of the high-potassic rock of the Chorukh-Dairon pluton occurred in the transitional subduction-related to post-collisional environment or even under an actual post-collisional regime. This allows distinguishing two pulses of ore-bearing Carboniferous-Permian high-potassic calc-alkaline to shoshonitic series magmatism in the Middle Tien Shan. Consistently, there is a metallogenic evolution in the region that was expressed in the transition from porphyry Cu-Mo-Au deposits associated with subduction-related potassic magmatism, and likely evolving toward epithermal Au-Ag deposits, to essentially tungsten (W-Mo-Cu-Au) deposits associated with younger potassic magmatism occurring rather in the post-collisional environment.
Journal Article
Did magmatism of the Central Atlantic Magmatic Province
Pre-Gondwana breakup configurations suggest that the Borborema Province of Northeast Brazil and the areas of present-day Gulf of Guinea in West/Central Africa formed a conjugate fit in the West Gondwana supercontinent. Pangea breakup was associated with extensive magmatism, e.g., emplacement of the Central Atlantic Magmatic Province (CAMP). CAMP manifested as dykes, sills, and flows in areas of present-day West Africa, South America, east coast of North America (USA and Canada), and in Europe. While the Borborema Province of Northeast Brazil was widely affected by pre-, syn-, and post-Pangea breakup magmatism (including CAMP), it is not clear why whole-time equivalents, i.e., similar magmatism, have not yet been reported in areas of present-day Jos Plateau, Benue Trough, and the Cameroon Line in the Gulf of Guinea. We gathered 467, 444, and 125 radioisotope age data, respectively, for the Gulf of Guinea, Northeast Brazil, and global CAMP systems. In addition to confirming the Hettangian (201.43 ± 0.15 Ma) global CAMP peak activity, the assembled data confirm a later 'tailing' CAMP in Guinea, Northeast Brazil (Maranhão) and Canada, that occurred at ~ 192.5 ± 0.5 Ma. Very few mafic dykes in the Gulf of Guinea have been dated. The assembled data show that one of them at Kendem on the Cameroon Line gave a .sup.40Ar-.sup.39Ar plateau age that falls within the tailing CAMP window. When compared to 1100 and 490 geochemical data collected for the Gulf of Guinea and global CAMP, respectively, this Lower Jurassic Cameroon Line dyke closely resembles CAMP in Northeast Brazil. We use the radioisotope age and geochemical similarity between the Cameroon Line dyke from Gulf of Guinea and CAMP from Northeast Brazil to argue for the need to investigate a more eastward extension of CAMP than is presently known. Currently available radioisotope age data on the Cameroon Line suggest that the onset of magmatism on different centers of the line may have a space-time relationship. This has implications for deep mantle involvement in the magmatism of the volcanic chain and therefore needs further investigation.
Journal Article
Isotopic Systematics of the Sikhote-Alin Basic-Hyperbasic Complexes
-The paper demonstrates the possibility of application of the .sup.143Nd/.sup.144Nd-Sm/Nd and Nb/Y-Zr/Y diagrams to systematics of basic-ultrabasic complexes of different age: Paleozoic Kalinovsky, Cambrian Sergeevsky and Vladimiro-Aleksandrovsky, and Jurassic and Paleocene ones. The position of data points of the Kalinovsky, Sergeevsky, and Vladimiro-Aleksandrovsky complexes in the diagrams indicates their derivation from a primitive mantle-type (BSE) source, the derivatives of which are frequently associated with Cu, Ni, Co, and PGE mineralization. The position of data points of metabasic rocks of the Avdokimovsky complex and peridotite rocks of the Dalny Kut massif in these diagrams suggests that they have originated from depleted mantle and are promising for the discovery of PGE-bearing chromite mineralization. Data points of Paleocene explosive structures of Sikhote-Alin in the Nb/Y-Zr/Y diagram fall on the trend of recycled crust as a source. This explains the alkaline (to subalkaline) type of magmatism and the high gas saturation of magmas. The explosive structures resemble lamproite pipes, while their rocks are geochemically and mineralogically close both to lamproites and kimberlites.
Journal Article
The Age of the Early Formation Stage of the Khovu-Aksy Ag-Bi-Cu-Ni-Co Deposit Geochronological Studies of Garnet
Mineralogical and U-Pb (ID-TIMS) geochronological studies of garnets from three types of scarn associations of the Khovu-Aksy Ag-Bi-Cu-Ni-Co deposit (Republic of Tuva) are carried out. The U-Pb garnet age estimate (404 ± 2 Ma) is close to the Early Devonian stage of basite and alkaline-basite magmatism identified within the Tuva trough of the Altai-Sayan folded area. The age of the scarn formation and the associated early stage of mineralization of the Khovu-Aksy Ag-Bi-Cu-Ni-Co deposit has been established for the first time.
Journal Article