Subsequent Events - Proportions of total Payable Copper (Details)	Mar. 20, 2023 T
Subsequent Event
Threshold Quantity of Refined Copper delivered to the Purchaser	33,000
Redemptions Backstop Facility \| Subsequent Event
Subsequent Event
Closing to 1st Anniversary of the Closing Date	0.00%
1st Anniversary of the Closing Date to 5th Anniversary	3.00%
5th Anniversary until 33,000 metric tonnes of Refined Copper delivered to the Purchaser (the "Threshold Quantity")	4.875%
Thereafter from the date that the Threshold Quantity has been met	2.25%

The percentage of payable copper, time period, closing to first anniversary of closing date.

No definition available.

Name:	mtal_PercentageOfPayableCopperTimePeriodClosingToFirstAnniversaryOfClosingDate
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of payable copper, time period, fifth anniversary until threshold quantity delivered to Purchaser.

+ References

No definition available.

+ Details

Name:	mtal_PercentageOfPayableCopperTimePeriodFifthAnniversaryUntilThresholdQuantityDeliveredToPurchaser
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of payable copper, time period, first anniversary of closing date to fifth anniversary.

+ References

No definition available.

+ Details

Name:	mtal_PercentageOfPayableCopperTimePeriodFirstAnniversaryOfClosingDateToFifthAnniversary
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of payable copper, time period, thereafter from the date that threshold quantity has been met.

+ References

No definition available.

+ Details

Name:	mtal_PercentageOfPayableCopperTimePeriodThereafterFromDateThatThresholdQuantityHasBeenMet
Namespace Prefix:	mtal_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The threshold quantity of refined copper to be delivered to Purchaser.

+ References

No definition available.

+ Details

Name:	mtal_ThresholdQuantityOfRefinedCopperToBeDeliveredToPurchaser
Namespace Prefix:	mtal_
Data Type:	dtr-types:massItemType
Balance Type:	na
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: