Early Cretaceous granitoids of the Samarka terrane (Sikhote-Alin’): geochemistry and sources of melts

Abstract

We present new data on the geologic position, composition, and isotope characteristics of the Early Cretaceous granitoids of the Samarka terrane, Sikhote-Alin’, formed on a transform continental margin. Geological and geochronological data show that these granitoids were generated at two stages of magmatism: in the first half (Hauterivian–Barremian, 130–123 Ma) and second half (Albian–Cenomanian, 110–98 Ma) of the Early Cretaceous. Granitoids of the first stage form an autonomous (free of basic precursors) unimodal melanogranite–granite association and are characterized by normal alkalinity with domination of K over Na, low contents of Ca, and elevated contents of Al2O3. By composition, these are S-granites with a model Nd age of ∼1.3 Ga. Granitoids of the second stage are of more diverse petrogeochemical types. They show wider variations in K/Na and A/CNK, are richer in Ca and, sometimes, Sr, and are poorer in P than the granitoids of the first stage. Their compositions form a continuous trend from S- to I-granites, and their model Nd age is ≤1.2 Ga. Comparison of the petrochemical, trace-element, and isotope characteristics of the Early Cretaceous granitoids and upper-crustal rocks (sandstones and siltstones of the turbidite matrix of a Jurassic accretionary prism and basalts from the inclusions in it) of the Samarka terrane and the coeval garrboids has shown that the potassic S-granitoids formed at the early (Hauterivian–Barremian) stage of magmatism as a result of the anatexis of upper-crustal sedimentary rocks. At the late (Albian–Early Cenomanian) stage, the intrusion of mantle magmas led to a temperature increase in the lower crust, which favored more active anatexis, involvement of high-melting substrates (oceanic basalts) in the granite formation, and interaction of mantle and crustal magmas. This resulted in a great diversity of granitoids (from S- to I-type).

The Cretaceous Turn of Geological Evolution: Key Evidence from East Asia

“…Our planet released 'escaped vapor' at the beginning of its seasonal contraction. Formation of the colossal petroleum reserves sourced by the Aptian-Turonian strata (about 1/3 of all the The Far Eastern Russia changes are presented after Baskina et al, 2006;Berdnikov and Karsakov, 1999;Chashchin et al, 2014;Faure et al, 1994;Geological …, 2014;Golozoubov et al, 2006;Jahn et al, 2015;Krasilov, 1967;Kruk et al, 2014;Markevich et al, 2000;Markevich, 1995;Oleynikov et al, 1990;Podolyan et al, 1997;Prikhod'ko et al, 2009;Sakhno et al, 2011;Sharudo, 1972;Simanenko et al, 2006;Volynets, 2009;Wu et al, 2017. world's oil and gas reserves) was one of the great economic results of this escape (Klemme and Ulmishek, 1991;Larson, 1991). Biogenic sedimentation, which predominated in the Early Mesozoic oceans, started being replaced by terrigenous deposits at about 120 Ma, when oceanic red clays appeared (Hu et al, 2012;and references therein).…”

“…The major orogenic phase, that finally consolidated the Sikhote-Alin terranes, happened during the late Aptianearly Albian (115-110 Ma). This event is reflected in isotopic dating of mica from the Anyuy metamorphic dome (Faure et al, 1995;Kruk et al, 2014) and hydrocarbon metasomatic rocks from the Dal'negorsk ore district (Baskina et al, 2006), that are close to the mid-Cretaceous plate reorganization in both the Pacific and more globally (Matthews et al, 2012;Vaughan, 1995).…”

“…This was accompanied by S-type collisional granites (Valanginian-Hauterivian) containing methane-rich fluid inclusions (Berdnikov and Karsakov, 1999) and then transitional Sand I-type granites of unclear (transformed?) geodynamic nature (Kruk et al, 2014). This unusual magmatic suite was replaced by Upper Cretaceous subduction-related volcanics forming the East Sikhote-Alin Belt and the Alchan zone and associated granitic intrusions (geological processes in the lithospheric plates subduction, collision, and slide environments, 2014; Jahn et al, 2015).…”

Zircon U–Pb dating and whole‐rock geochemistry of volcanic rocks in eastern Heilongjiang Province, NE China: Implications for the tectonic evolution of the Mudanjiang and Paleo‐Pacific oceans from the Jurassic to Cretaceous

“…The Sikhote‐Alin terranes were accreted one by one to the eastern margin of the Bureya‐Jiamusi‐Khanka Block before the Late Cretaceous (Golozoubov, Markevich, & Bugdaeva, ; Khanchuk et al, , ). Cretaceous to Cenozoic magmatism is widespread in the whole area, which is mainly recorded by plutons and their extrusive equivalents, in which most of them are rhyolitic to andesitic (Jahn et al, ; Kruk et al, ; Figure ). The known zircon U–Pb ages of the magmatic rocks range from the Early Cretaceous in the west to Paleogene in the southeast (Jahn et al, ; Khanchuk et al, ; Tang et al, ).…”

“…For instance, previous studies showed that the volcanic rocks with ages of 135 to 110 Ma were mainly located in the western NE China (mainly in the Great Xing'an Range and Songliao Basin). However, recent studies reveal that the arc‐related granitoids in the western the Sikhote‐Alin area also have ages from 135 to 110 Ma (Cheng et al, ; Jahn et al, ; Kruk et al, ). Thus, the migration of magmatism in NE Asia should include both the continental arc and back‐arc areas, like suggested by the third model (M. Sun et al, ).…”