PhD Position — Silica Precipitation in Alkaline Lakes as an Analogue for Early Earth Chert Formation

IACT-CSIC (Granada, Spain) has a job opening for a PhD Student to work on the topic “Silica Precipitation in Alkaline Lakes as an Analogue for Early Earth Chert Formation”

The position is funded for 3 years through the ERC Synergy Grant PROTOS and includes full social security coverage according to Spanish regulations.

About the PhD project

IACT-CSIC is offering a PhD position at the Laboratorio de Estudios Cristalográficos (LEC), Instituto Andaluz de Ciencias de la Tierra (IACT-CSIC, Granada, Spain), focused on the origin of silica deposits in alkaline lacustrine environments and their relevance to the formation and interpretation of Precambrian cherts on the early Earth.

The project will investigate whether silica deposits formed in modern alkaline lakes (“Magadi-type cherts”) can serve as robust analogues for silica deposition during the Hadean and early Precambrian, prior to the widespread emergence of biological silica cycling. In present-day systems such as Lake Magadi, silica precipitates under highly alkaline conditions (pH > 10), forming hydrated sodium silicates such as magadiite and kenyaite. These phases are hypothesized to act as precursors to microcrystalline silica, potentially representing an alternative abiotic pathway for chert formation beyond classical hydrothermal models.

The research will pursue three main objectives:

1. Characterization of silica precipitation pathways in modern alkaline lakes through field sampling and detailed mineralogical and geochemical analyses, with special emphasis on the environmental conditions controlling the formation of hydrated sodium silicates.
2. Controlled laboratory experiments designed to reproduce silica precipitation and early diagenetic transformations under high-pH conditions, simulating the evolution from dissolved silica to sodium silicates and ultimately to microcrystalline silica.
3. Comparative analysis with Precambrian cherts from selected Archean successions, including the Barberton Greenstone Belt and the Pilbara Craton, using petrographic observations and targeted geochemical proxies, including silicon isotopes where feasible.

By integrating field observations, experimental results and comparative geological analyses, the project aims to establish diagnostic criteria for identifying alkaline lacustrine silica deposits in the geological record. The expected outcome is a mechanistic framework contributing to improved models of Precambrian silica cycling, ancient sedimentary environments and plausible pathways for silica deposition on the early Earth.

Research Environment

The doctoral project is part of the ERC Synergy Grant PROTOS — The role of silica in the dawn of life on our planet. The successful candidate will work within the international and interdisciplinary PROTOS consortium and collaborate closely with researchers across several partner institutions.

Three research stays in laboratories of PROTOS partners are foreseen within the project framework:

• Studies on the geochemistry of Magadi Lake and their implications for silica precipitation will be done partially at the laboratory of Prof. Juan Manuel García Ruiz at Donostia International Physics Center, Donostia.
• Studies of early diagenetic transformations at the laboratories of Prof. Mark van Zuilen within the Marine Biodiversity Group at Naturalis Biodiversity Center, Leiden;
• The isotopic characterization will be done at the group of Prof. Stefan V. Lalonde in the Geo-Ocean Laboratory of the European Institute for Marine Studies, Brest.

The candidate will join the Laboratorio de Estudios Cristalográficos, part of the Instituto Andaluz de Ciencias de la Tierra (IACT-CSIC), a multidisciplinary Earth science institute of the Spanish National Research Council (CSIC). LEC conducts research on crystallization processes, mineral self-organization, geochemistry and pattern formation in natural systems, combining field observations, laboratory experimentation and theoretical approaches. The group provides a highly interdisciplinary environment with expertise spanning crystallography, mineralogy, geochemistry and Earth sciences, as well as access to advanced analytical facilities and international collaborations.

Candidate profile