Types of available ores and metallurgy on a "newly" terraformed planet?

Question

I am developing a story set on an exoplanet that was colonized by spacefaring humans but has long since lost all contact with the homeworld due to some unknown catastrophe at least 12,000 years before the present. The current civilizational level is pre-electrical, although some more forms of power that do not require electricity may possibly be available (i.e., primitive steam power, wind/water-driven mechanical power for things like milling, maybe pneumatic power).

The planet is tidally locked within the habitable zone of an M-type red dwarf star, which itself orbits an M-type yellow star at approximately 1.5 AU. It has a roughly Earthlike silica and metal composition, but it is a stagnant lid planet (no plate tectonics). Roughly 90% of its surface is covered with relatively shallow oceans (average depth of about 100m), and the only land masses are large volcanic island chains formed through volcanic hotspots underneath the shifting stagnant lid (this is how mid-plate islands like the Hawaiian islands are formed; also the large shield volcanoes on Mars like Olympus Mons).

It is my understanding that due to the lack of plate tectonics, some common metals and metal ores may be scarce or difficult to access on land on such a planet. Although from the research I've done, the volcanic activity would still tend to deposit some of the basic metals such as copper, nickel, iron, tin, etc., just not in the amounts present in many places on Earth. The Hawaiian islands, for instance, don't have a lot of easily mineable resources, it seems.

Furthermore, this planet was only recently (on a geological timescale) terraformed, beginning approximately 50,000 years before present. Before this process began, it was a dead planet and therefore has no fossil fuel deposits like coal which could be used for metallurgy.

My question is, given all of this background information, what level of metallurgy would it be feasible for a pre-electrical civilization on this planet to have? Real-life Polynesian cultures were at pre-Bronze Age levels of metallurgy. On the other hand, other volcanic hotspot islands such as Iceland have supported Iron Age to modern civilizations, although I'm not sure how much of that is due to importing resources from other parts of the world.

Answer 1

You can have all resources that do not require life to form. Beside lacking fossil fuels you also will not have large deposits of white chalkstone like at the coast of Dover which are formed from ancient sea shells and the like.

However, many lifeless solar system bodies are covered in hydrocarbons, tars of complex organic substances and soot-like amorphous carbon. Organic compounds, while overall rare in the Earth crust, are extremely common in the universe. Your planet could have orders of magnitude more "fossil fuel" in the ground than Earth, provided that conditions in its past - before it was terraformed - were reducing, so that the carbon compounds did not oxidise.

By the way, you do not need coal for metallurgy. In 18th century Europe, at the start of the industrial revolution, people often used char for metallurgical purposes. The Japanese had a technique to make high quality char which in consistence came close to bituminous coal.

If, as you say, the planet has less geological activity (and less land) than Earth, then you may have a smaller amount of ore deposits. Many ore forming processes need water to be effective (including those of volcanic nature). Therefore, much depends on if there was liquid water present before the planet was terraformed.

You also could have had a liquid other than water, ammonia for example, hydrocarbons or sulfur compounds. Solvents other than water would allow for exotic evaporite ores and when there was a variety of different fluids in different mixtures you could get a rich inventory of minerals, because substances have different solubility in different solvents. Which liquids were present on the planet depends on the atmospheric conditions it had before terraforming. A lack of atmosphere would have kept the planet frozen on one side and fluids would have only been possible (and likely) underground. A thick atmosphere on the other hand would even allow things like oceans of carbon dioxide.

If you want your planet to have plenty of ore despite little geologic activity I would recommend such a "wet" past with complex climatic conditions in an overall reducing environment and much opportunity for sedimentary processes to go on.

Another important point is the bulk composition of the planet. Earth for example has much less magnesium, chromium, manganese, chlorine and fluorine in its crust than Mars. If a planet has a high bulk abundance of an element than you get a higher probability to have ores of this element.

When the planet is rich in sulfur then chalkophile elements have a higher chance to form sulfide deposits. Those elements include copper, zinc, silver, mercury, tin, lead to name the more important ones. Siderophile elements like nickel and cobalt can form sulfide deposits as well. In highly reducing conditions even lithophile elements can exist as sulfides, for example magnesium sulfide (niningerite) or chromium sulfide (brezinaite). Sulfide deposits on Earth need volcanism, but in case liquid hydrogen sulfide (a common volatile in the solar system) was originally present on the planet, then sulfide deposits of sedimentary or evaporite nature could exist as well.

A high carbon content in the ground could enable naturally occurring carbothermic reactions allowing for deposits of native metal, especially iron and other transition metals, to form. Earth is pretty much depleted in carbon despite its importance for life.

M-stars are not as stable as the Sun. They periodically produce flares which increase their luminosity by orders of magnitude. Any life on a planet in their orbit, if it can exist at all, must have adaptations to survive such occurrences.

I am not sure if the rather close binary system that you describe even allows for a dynamically stable orbit in the habitable zone around the M-dwarf.

One last point: the technological stage of a local society has little to do with locally available resources. Icelanders did not invent metallurgy on their own, Iceland was settled by people who already knew how to make iron. Polynesia on the other hand remained a stone age culture simply because they had no trade contact with any society that had iron tools.

Answer 2

Sidestepping most of the planetary formation / ore distribution matters:

You could cheat and have had biological concentration / diffusion of the elements

Almost every first row transition metal, as well as most p-block elements, are used in biochemistry. The ones that aren't, aren't because they are so scarce.

Think: Magnesium, Titanium, Chromium, Molybdenum, Iron, Cobalt, Copper, and Zinc.

Your terraforming may have used engineered bacteria that either needed an element and gradually diffused it to the point that there are no good ores, or deliberately concentrated them.

The elements that don't work so well for this are the heavy p block metals (tin, lead, arsenic), tungsten, mercury, silver, and gold. Although you could find excuses for bioaccumulating them too. Which just leaves aluminium, which given your lack of both electricity and fossil fuels for high temperature reactions, is probably not that feasible anyway.

With enough time, you might match the Victorian era, but you're more likely stuck in the early modern era with expensive steel

This depends on their economy. I'm just going to assume out of hand that you can get into the Iron Age using the same pathway as we did; copper from easy to process ores, arsenic and tin bronze, then iron.

To get into the Victorian era or just beyond, where steel becomes plentiful and trace elements start to get used in controlled fashion to create new steels and bronzes, you do need some readily available source of energy, and some available source of carbon, as well as some BIG inorganic calcium carbonate deposits. More on CaCO3 in a minute.

Does your civilisation produce e.g. huge amounts of sugar? Or lipids? Or have really great forestry? Any of these could probably produce the carbon you need. That's your main obstacle. It needs to be really cheap; even then, steel will be very expensive comparative to Earth.

The limestone problem

This is actually a pretty serious problem for bulk steelmaking. Limestone is formed biologically, and inorganic calcium carbonates, etc, come mostly from geothermal fields. See e.g. this question.

Maybe you can handwave a little and say that Ca was a bit more common and this planet had a lot of CO2 and a high pH in the past? Or have some volcanic fields that just happened to produce some limestone superdeposits?