Va. Makrygina et al., Correlation of Precambrian basic magmatism in lithospheric blocks of Western and Northern Prebaikalia (according to geochemical data), GEOL GEOFIZ, 41(3), 2000, pp. 414-427
A comparison is made between the geochemical compositions of metabasic rock
s from Western and Northern Prebaikalia. In geochemistry metagabbros from t
he Kocheriki block are most similar to metabasic rocks of the Nyurundukan s
eries, various parts (plates) of which are considered to have formed in the
settings of a back-are basin and a primitive island are. In addition, the
Kocheriki gabbros are similar to metatholeiites of the Ol'khon series, whic
h also formed in the setting of a marginal sea but, unlike the gabbros, are
associated with abundant metasediments and the Anga volcanosedimentary ser
ies - the product of a mature island are. The Kocheriki block passed throug
h two stages of metamorphism. It formed in space and time separately from t
he Sarma black and merged with the latter by the second stage of metamorphi
sm, 445 Ma ago, as a result of tectonic processes. Metabasic rocks of the S
arma block are compositionally close to gabbros of the Kocheriki block, and
dikes of basic composition in granites of the Primorsky complex are somewh
at closer to metabasic rocks of the Boguchany block in Northern Prebaikalia
, which seem to be of within-plate origin. "Diorite-like" dikes are most li
kely the products of metasomatic reworking of basic dikes and granites duri
ng cataclasis. Dikes in granites might have formed synchronously with the c
onformable horizons of basic rocks of the Sarma series.