The significance of cherts as markers of Ocean Plate Stratigraphy and paleoenvironmental conditions: New insights from the Neoproterozoic–Cambrian Blovice accretionary wedge, Bohemian Massif

Multi-stage metal enrichment and formation of gold mineralization in black shales: the role of high heat flow in a rift setting

“…1c). The chert forms blocks up to several hundred meters in length, enclosed within siliciclastic matrix, which is dominated by finegrained graywacke, siltstone, and shale (Ackerman et al 2023). The chert-graywacke unit has been interpreted as an olistostrome formed presumably on a trench slope, overlain by a monotonous graywacke succession (Hajná et al 2019).…”

Seawater silica cycling and chert formation at the Neoproterozoic–Cambrian transition: Insights from δ30Si and Ge/Si systematics of hydrothermal cherts from the Bohemian Massif

“…1). The Belts 1-3 consist of predominant graywacke and shale with subordinate black shale (e.g., Pašava et al, 2021), chert (Belt 1 and 2; Ackerman et al, 2023) and limestone (Ackerman et al, 2022), and abundant basaltic blocks of MORB and OIB composition (Ackerman et al, 2019;Pin and Waldhausrová, 2007). In contrast, the Belt II-III section almost devoid of basaltic rocks is represented by rather uniform sedimentary successions dominated by graywacke-shale, sometimes accompanied by black shales (Belt II; e.g., Pašava, 2000); the graywacke-chert Belt I was interpreted as an olistostrome formed at the outer trench slope of the subducted slab (Hajná et al, 2019).…”

“…In contrast, the Belt II-III section almost devoid of basaltic rocks is represented by rather uniform sedimentary successions dominated by graywacke-shale, sometimes accompanied by black shales (Belt II; e.g., Pašava, 2000); the graywacke-chert Belt I was interpreted as an olistostrome formed at the outer trench slope of the subducted slab (Hajná et al, 2019). Recent studies (Ackerman et al, 2023(Ackerman et al, , 2022 argued that Blovice accretionary complex is an Ocean Plate Stratigraphy mélange (e.g., Wakita, 2015), where material derived from a lower oceanic plate (basalt, chert, limestone) was mixed with the predominantly arc-derived siliciclastic detritus derived from the upper plate (Fig. 1).…”

“…1). Recently, Ackerman et al (2023) estimated the chert deposition in the Blovice accretionary complex between ~591 and 547 Ma and identified two major types based on their field relationship, petrography and elemental as well as isotope compositions: (1) deep-water cherts that are particularly abundant in Belt I and partly also in Belt 2 being formed on an outer trench slope of a subducted oceanic slab, and…”

“…In this study, we investigated Si isotope compositions and Ge/Si ratios in a suite of cherts from the late Neoproterozoic-early Cambrian Blovice accretionary complex (Teplá-Barrandian Unit, Bohemian Massif, Czech Republic) previously well-characterized in terms of their major/trace and Sr-C-O isotope compositions (Ackerman et al, 2023;Hajná et al, 2019). The collected data are used to (i) establish the nature of cherts and processes of their formation, (ii) identify the sources of Si and Ge, and (iii) discuss the possible effect of the Neoproterozoic-Cambrian transition on the combined Si isotope and Si-Ge elemental systematics of the cherts.…”